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Life in the Universe 

From the Miller Experiment to the 
Search for Life on other Worlds 

Edited by 

Joseph Seckhach, Julian Chela^Flores, 
Tobias Owen and Francois Raulin 

Springer Science+Business Media, B.V. 


Cellular Origin and Life in Extreme Habitats and Astrobiology 

Volume 7 

Series Editor: 

Joseph Seckbach 

Hebrew University of Jerusalem, Israel 

Life in the Universe 

From the Miller Experiment to the 
Search for Life on other Worlds 

Edited by 

Joseph Seckbach 

Hebrew University of Jerusalem, Israel 

Julian Chela-Flores 

The Abdus Salam International Center for Theoretical Physics, 
Trieste, Italy 

and Institute de Estudios Avanzados (IDEA), 

Caracas, Venezuela 

Tobias Owen 

Institute for Astronomy, Honolulu, Hawaii, U.S.A. 

Francois Raulin 

LISA, Universites Paris 12 & Paris 7, 

Faculte des Sciences et Technologie, France 


A C.I.P. Catalogue record for this book is available from the Library of Congress. 

ISBN 978-1-4020-3093-2 ISBN 978-94-007-1003-0 (eBook) 
DOI 10.1007/978-94-007-1003-0 

Cover artwork by Malte Reimold, von Kiedrowski laboratory, Ruhr-University Bochum, Germany. 

Printed on acid-free paper 

All Rights Reserved 

© 2004 Springer Science+Business Media Dordrecht 
Originally published by Kluwer Academic Publishers in 2004 
Softcover reprint of the hardcover 1st edition 2004 

No part of this work may be reproduced, stored in a retrieval system, or transmitted 

in any form or by any means, electronic, mechanical, photocopying, microfilming, recording 

or otherwise, without written permission from the Publisher, with the exception 

of any material supplied specifically for the purpose of being entered 

and executed on a computer system, for exclusive use by the purchaser of the work. 


This book is dedicated to Professor Stanley L. Miller in honor of his 50th jubilee 
experiments in the prebiotic origin of life. 

Professor Stanley Miller with the editor Joseph Seckbach during the Trieste-2003 
conference on Life in the Universe. 


Dedication v 

Biodata of editors xv 

Preface by the editors xxi 

Acknowledgements xxiii 

Group photograph and List of Attendees xxiv 

I. Opening 

Introduction to Life in the Universe 3 

T. Johnson 

The Abdus Salam Lecture 7 

H. Baltscheffsky 

The Beginning of Chemical Evolution Experiments 9 

S. Miller, J. L. Bada and A. Lazcano 

An Overview of Cosmic Evolution 17 

George V. Coyne 

Physical Phenomena underlying the Origin of Life 27 

Juan Perez-Mercader 

II. Where did the Chemical Elements Come From and When did Life Begin? 

The Origin of Biogenic Elements 55 

E. Matteucci and C. Chiappini 

Thermochemistry of the Dark Age 59 

D. Puy 

Searching for Oldest Life on Earth; A Progress Report 63 

S. Moorbath and B. S. Kamber 

The European Exo/Astrobiology Network Association 67 

Andre Brack 

III. Physical Constraints on the Origin of Life 

The Origin of Biomolecular Chirality 73 

J. Rivera Islas, J. C. Micheau and T. Buhse 



Salam Hypothesis and The Role af Phase Transition in Amino Acids 79 

W. Wang, N. Yao, Y. Chen and P. Lai 

A Mechanism for the Prebiotic Emergence of Proteins 83 

H. P. De Vladar, R. Cipriani, B. Scharifker and J. Bubis 

Functional, Self-Referential Genetic Coding 89 

R. C. Guimaraes and C. H. C. Moreira 

Importance of Biased Synthesis in Chemical Evolution Studies 93 

A. Negron-Mendoza, S. Ramos-Bernal and F. G. Mosqueira 

When Did Information First Appear in the Universe 97 

J. G. Roederer 

IV. From the Miller Experiment to Chemical and Biological Evolution 

Prebiotic Organic Synthesis and the Emergence of Life 103 

L. Delaye, A. Becerra, A. M. Velasco, S. Islas and A. Lazcano 

Origin and Evolution of Very Early Sequence Motifs in Enzymes 107 

H. Baltscheffsky, B. Persson, A. Schultz, J. R. Perez-Castineira and 

M. Baltscheffsky 

The Lipid World: From Catalytic and Informational Headgroups to 

Micelle Replication and Evolution without Nucleic Acids Ill 

A. Bar-Even, B. Shenhav, R. Kafri and D. Lancet 

Coenzymes in Evolution of the Rna World 115 

M. S. Kritsky, T. A. Telegina, T. A. Lyudnikova and Yu. L. Zemskova 

The Role of Heat in the Origin of Life 119 

P. R. Bahn, A. Pappelis and R. Grubbs 

A Possible Pathway for the Transfer of Chiral Bias from Extraterrestrial 

C“-Tetrasubstituted a-Amino Acids to Proteinogenic Amino Acids 121 

M. Crisma, A. Moretto, F. Formaggio, B. Kaptein, Q. B. Broxterman and 
C. Toniolo 

Prebiotic Polymerization of Amino Acids. A Makov Chain Approach 123 

F. G. Mosqueira, S. Ramos-Bernal and A. Negron-Mendoza 

The Electrochemical Reduction of C 02 to Formate in Hydrothermal Sulfide 

Ore Deposit as a Novel Source of Organic Matter 125 

M. G. Vladimirov, Yu. F. Ryzhkov, V. A. Alekseev, V. A. Bogdanovskaya, 

V. A. Otroshchenko and M. S. Kritsky 


Towards a Chronological Order of the Amino Acids 127 

W. J. M. F. Collis 

Origin and Evolution of Metabolic Pathways 129 

M. Brilli and R. Fani 

Conserved Oligopeptides in the Rubisco Large Chains 133 

P. B. Vidyasagar, P. Shil and S. Thomas 

On The Question of Convergent Evolution in Biochemistry 135 

A. A. Akindahunsi and J. Chela-Elores 

Diversity of Microbial Life on Earth and Beyond 139 

J. Seckbach 

V. Alternative Scenarios for the Origin and Evolntion of Life 

Mineral Surfaces as a Cradle of Primordial Genetic Material 145 

E. Gallori, E. Biondi and M. Eranchi 

Adsorption and Self-Organization of Small Molecules on Inorganic Surfaces 149 

D. G. Fraser 

Studies on Copper Chromicyanide as Prebiotic Catalyst 153 

Kamaluddin and S. R. Ali 

Phosphate Immobilization by Primitive Condensers 157 

F. De Souza-Barros, M. B. M. Monte, A. C. P. Duarte, 

J. A. P Bonapace, M. R. D. Amaral Jr., R. B. Levigard, 

Y. A. Ching-San Jr., C. S. Costa and A. Vieyra 

Adsorption and Catalysis of Nucleotide Hydrolysis by Pyrite in Media Simulating 

Primeval Aqueous Environments 161 

A. Vieyra, A. C. Tessis, M. Pontes-Buarque, J. A. P. Bonapace, M. Monte, 

H. S. De Amorim and F. De Souza-Barros 

VI. Cosmological and Other Space Science Aspects of Astrohiology 

Dust and Planet Formation in the Early Universe 167 

G. Vladilo 

Quasar Absorption-Line Systems and Astrohiology 169 

G. Vladilo 

A New Search for Dyson Spheres in the Milky Way 173 

D. Minniti, E. Capponi, A. Valcarce and J. Gallardo 


Space Weather and Space Climate 177 

M. Messerotti 

VII. Planetary Exploration in our Solar System: The Interstellar Medium, Micro-Meteorites 
and Comets 

Spontaneous Generation of Amino Acid Structures in the Interstellar Medium 183 

U. J. Meierhenrich 

Experimental Study of the Degradation of Complex Organic Molecules. Application 
to the Origin of Extended Sources in Cometary Atmospheres 187 

N. Eray, Y. Benilan, H. Cottin, M.-C. Gazeau and E. Raulin 

Eate of Glycine During Collapse of Interstellar Clouds and Star Eormation 191 

S. K. Chakrabarti, S. Chakrabarti and K. Acharyya 

Eormation of Simplest Bio-Molecules during Collapse of an Interstellar Cloud 195 

K. Acharya, S. K. Chakrabarti and S. Chakrabarti 

Chemical Abundances of Cometary Meteoroids from Meteor Spectroscopy 201 

J. M. Trigo-Rodriguez, J. Llorca and J. Oro 

VIII. Earth Analogues of Extraterrestrial Ecosystems 

Viable Halobacteria from Ancient Ocea 207 

H. Stan-Lotter, C. Radax, S. Leuko, A. Legat, C. Gruber, 

M. Pfaffernhuemer, H. Wieland and G. Weidler 

Mars-Like Soils in the Yungay Area, the Driest Core of the 

Atacama Desert in Northern Chile 211 

R. Navarro-Gonzalez, E. A. Rainey, P. Molina, D. R. Bagaley, 

B. J. Hollen, J. De La Rosa, A. M. Small, R. C. Quinn, E. J. Grunthaner, 

L. Caceres, B. Gomez-Silva, A. Buch, R. Sternberg, P. Coll, 

E. Raulin and Ch. P. McKay 

The Discovery of Organics in Sub-Basement Eossil Soils Drilled in the 
North Pacific (Odp Leg 197): Their Model Eormation and Implications for 

Astrobiology Research 217 

R. Bonaccorsi and R. L. Mancinelli 

Silica-Carbonate Biomorphs and the Implications for Identification 

of Microfossils 221 

A. M. Carnerup, S. T Hyde, A-K. Larsson, A. G. Christy and J. M. Gracfa-Ruiz 

Some Statistical Aspects Related to the Study of Treeline in Pico De Orizaba 223 

L. Cruz-Kuri, C. P. McKay and R. Navarro-Gonzalez 


IX. On the Question of Life on Mars and on the Early Earth 

The Beagle 2 Lander and the Search for Traces of Life on Mars 227 

A. Brack, C. T. Pillinger and M. R. Sims 

Minimal Unit of Terraforming an Alternative for Remodelling Mars 233 

H. O. Pensado Diaz 

Early Archaean Life 239 

F. Westall 

Extraterrestrial Impacts on Earth and Extinction of Life in the Himalaya 245 

V. C. Tewari 

Palaeobiology and Biosedimentology of the Stromatolitic Buxa Dolomite, 

Ranjit Window, Sikkim, Ne Lesser Himalaya, India 249 

V. C. Tewari 

X. Searching for Extraterrestrial Life, Europa, Titan and Extrasolar Planets 

Searching for Extraterrestrial Life 253 

T. Owen 

Search for Bacterial Waste as a Possible Signature of Life on Europa 257 

A. B. Bhattacherjee and J. Chela-Flores 

Sulfate Volumes and the Fitness of Supcrt92 for Calculating 

Deep Ocean Chemistry 261 

S. Vance, E. Shock and T. Spohn 

The Case for Life Existing Outside of our Biosphere 265 

R. S. Gatta 

Application of Molecular Biology Techniques to Astrobiology 269 

R. S. Gatta and J. Chela-Flores 

Titan 275 

F. Raulin, J-P. Lebreton and T. Owen 

Chemical Characterization of Aerosols in Simulated Planetary Atmospheres 281 

S. I. Ramirez, R. Navarro-Gonzalez, P. Coll and F. Raulin 

Observation, Modeling and Experimental Simulation: Understanding Titan’s 

Atmospheric Chemistry Using These Three Tools 287 

J.-M. Bernard, P. Coll, C. D. Pintassilgo, Y. Benilan, 

A. Jolly, G. Cernogora and F Raulin 


Exobiology of Titan 293 

M. Simakov 

XI. The Search for Extraterrestrial Intelligence (SETI) 

Seti-Italia 299 

S. Montebugnoli, J. Monari, C. Bortolotti, A. Cattani, A. Maccaferri, 

M. Poloni, A. Orlati, S. Righini, S. Poppi, M. Roma, M. Teodorani, 

C. Maccone, C. B. Cosmovici and N. D’Amico 

Seti on the Moon 303 

C. Maccone 

Proposing a United Nations Secretary General Seti International 

Advisory Board 307 

G. Picco, G. Genta, P. Galeotti and D. Noventa 

Some Engineering Considerations on the Controversial Issue of Humanoids 311 

G. Genta 

XII. The Search for Evolution of Intelligent Behavior and Density of Life 

The New Universe, Destiny of Life, and the Cultural Implications 319 

S. J. Dick 

Evolution of Intelligent Behavior 327 

J. Chela-Elores 

Evolution of Language as Innate Mental Eaculty 333 

K. T. Shah 

How Advanced is Et? 335 

P. Musso 

XIII. Epistemological and Historical Aspects of Astrobiology 

Chance or Design in the Origin of Living Beings 341 

R. Vicuna and A. Serani-Merlo 

Astrobiology and Biocentrism 345 

R. Aretxaga 

Analysis of the Works of the German Naturalist Ernst Haeckel 

(1834-1919) on the Origin of Life 349 

F. Raulin-Cerceau 


A Reexamination of Alfonso Herrera’s Sulfocyanic Theory 

on the Origin of Life 353 

E. Silva, L. Perezgasga, A. Lazcano and A. Negron-Mendoza 

Determinism and the Proteinoid Theory 357 

A. Pappelis and P. R. Bahn 

Glimpses of Trieste Conferences on Chemical Evolution and Origin of Life 361 

M. S. Chadha 

List of Participants 365 

Index 375 

Index of Authors 385 

Biodata of Stanley Miller, dedicatee of the volume ‘"Life in the Universe” 

Professor Stanley Miller, an American chemist and biologist was born in Oakland, 
California. He was educated at University of California (B.Sc. in 1951), and then at Univer- 
sity of Chicago (where he was a student of Nobelist Harold Urey, and received his Ph.D. in 
chemistry in 1954). He was an assistant professor (1958-1960), associate professor (1960- 
1968), and then full professor of chemistry at the University of California, San Diego (from 
1968). His research deals primarily with the origin of life and he is considered a pioneer 
in the field of exobiology. He has also studied the natural occurrence of clathrate hydrates 
and the use of hydrogen as a commercial fuel. In the 1950’s, Urey theorized that the early 
atmosphere of the Earth was probably like the atmosphere now present on Jupiter — i.e., rich 
in ammonia, methane, and hydrogen. Miller, working in his laboratory at the University 
of Chicago, demonstrated in 1953 that when exposed to an energy source such as spark 
discharges these compounds and water can react to produce amino acids essential for the 
formation of living matter. This watershed experiment gave the first demonstration that 
the building blocks of life could be produced spontaneously from a planetary environment. 
The current consensus is that the Earth never had an atmosphere that was so reducing, but 
similar results have been obtained with less reducing gas mixtures. Indeed, this experiment 
has been repeated tens of thousands of times with different mixtures of gases, and the basic 
results have been spectacularly confirmed by the discovery of amino acids in meteorites. 
Professor Miller is a member of the National Academy of Science and has received nu- 
merous honors and medals, including the Oparin Medal of the International Society for the 
Study of the Origin of Life (1983). He served as the President of the above society (ISSOL) 
from 1986 to 1989. 


Biodata of Joseph Seckbach, author of the chapter “Diversity of Microbial Life on Earth 
and Beyond” and editor (with co-editors Julian Chela-Flores, Tohias Owen and Francois 
Raulin) of this book (Life in the Universe (2004). 

Professor Joseph Seckbach is the initiator and chief editor of Cellular Origins, Life in 
Extreme Habitats and Astrobiology ( COLE ) book series, and author of several chapters 
in this series. He earned his Ph.D. from the University of Chicago, Chicago, IL (1965) and 
spent his postdoctoral years in the Division of Biology at Caltech (Pasadena, CA). Then 
he headed at the University of California at Los Angeles (UCLA) a team for searching of 
extraterrestrial life. Dr. Seckbach has been appointed to the faculty of the Hebrew University 
(Jerusalem, Israel) performed algal research and taught Biological courses. He spent his 
sabbatical periods in Tubingen (Germany), UCLA and Harvard University and served at 
Louisiana State University (LSU), (1997/1998) as the first selected occupant of the John 
P. Laborde endowed Chair for the Louisiana Sea Grant and Technology transfer, and as a 
visiting Professor in the Department of Life Sciences at LSU (Baton Rouge, LA). 

Among his publications are books, scientific articles concerning plant ferritin (phyto- 
ferritin), cellular evolution, acidothermophilic algae, and life in extreme environments. He 
also edited and translated several popular books. Dr. Seckbach is the co-author (with R. 
Ikan) of the Chemistry Lexicon (1991, 1999) and other volumes, such as the Proceeding 
of Endocytobiology VII Conference (Freiburg, Germany, 1998) and the Proceedings of 
Algae and Extreme Environments meeting ( Trebon , Czech Republic, 2000). His recent 
interest is in Life origins and extremophilic environments of microorganisms. 


Biodata of Julian Chela-Flores (editor) 

Professor Chela-Flores current positions are: Staff Associate of the Abdus Salam Interna- 
tional Center for Theoretical Physics (ICTP), Trieste, Research Associate, Dublin Institute 
for Advanced Studies (DIAS) and Professor Titular, Institute of Advanced Studies (IDEA), 
Caracas. He is a Fellow of: The Latin American Academy of Sciences, The Third World 
Academy of Sciences, the Academy of Creative Endeavors (Moscow, Russia) and a Corre- 
sponding Member of the Academia de Fisica Matematicas y Ciencias Naturales (Caracas). 
Professor Julian Chela-Flores studied in the University of London, England, where he ob- 
tained his Ph.D. (1969) in quantum mechanics. He was a researcher at the Venezuelan 
Institute for Scientific Research (IVIC) and Professor at Simon Bolivar University (USB, 
Caracas) until his retirement in 1990. His particular area of expertise is astrobiology, in 
which he is the author of numerous publications in this new science, including some in 
the frontier between astrobiology and the humanities (philosophy and theology). Professor 
Chela-Flores has been the organizer of a series of Conferences on Chemical Evolution and 
the Origin of Life from 1992 till 2003 (and was the co-director from 1995 till 2003). From 
1992 till 1994 he worked in collaboration with Cyril Ponnamperuma. This series contin- 
ued Ponnamperuma’s College Park Colloquia on Chemical Evolution, which had started in 
Maryland, USA in the 1970s. All the proceedings of the present series of conferences have 
been published. In 1999 Professor Chela-Flores co-directed and edited the proceedings of 
an Iberoamerican School of Astrobiology in Caracas at the IDEA Convention Center. 



Biodata of Tobias Owen (editor) 

Tobias Owen is a Professor of astronomy at the Institute for Astronomy of the University 
of Hawaii. He studies the Planets, satellites and comets of our solar system using the giant 
telescopes on Mauna Kea and by means of deep-space missions. He has participated in the 
Viking Lander on Mars, the Voyager, Galileo, Deep Space 1 , Nozomi and Contour Missions. 
He is currently an Interdisciplinary Scientist and member of several experiment teams on 
the ESA-NASA Cassini-Huygens Mission to the Saturn System, an Associate Scientist 
on the Rosina team for the Rosetta Mission to Comet Churyumov-Gerasimenko, and a 
Science team member of the Kepler Mission to search for terrestrial planets. Professor 
Owen received his Ph.D. in astronomy from the University of Arizona in 1965. He has 
published over 250 scientific articles and has co-authored two textbooks: “The Search for 
Life in the Universe” (with Donald Goldsmith) and “The Planetary System” (with David 
Morrison). He was awarded the NASA Medal for Exceptional Scientific Achievement for 
his Viking study of the Martian atmosphere. 



Biodata of Francois Raulin (Editor) 

Francois Raulin is Full Professor at University Paris 12, and head of PCOS (Space Organic 
Physical Chemistry) group of LISA, Laboratoire Interuniversitaire des Systemes Atmo- 
spheriques a joint University Paris 7, University Paris 12 and CNRS laboratory of more than 
80 persons, working on terrestrial troposphere in relation to environmental problems and on 
extraterrestrial environments, in relation to exobiology ( ). 
He is Director of LISA since 1995 and , since 1999, of CNRS “Groupement de Recherche” 
in Exobiology (GDR Exobio), federation of laboratories working on Exobiology, affiliated 
to NAI ( 

He got a diploma of Engineer from the Ecole Superieure de Physique et Chimie Indus- 
trielles de la Ville de Paris in 1969, and a Doctorat d’Etat es Sciences Physiques (on the 
role of sulphur in prebiotic chemistry) from the Universite Paris 6 in 1976. He). 

His research helds are related to planetology and exo/astrobiology: organic chemistry 
in extraterrestrial environments (Titan, giant planets, comets and Mars) using laboratory 
experiments (experimental simulations, spectroscopy, GC techniques), theoretical modeling 
and observation (remove sensing and in situ space exploration). 

F. Raulin is IDS (InterDisciplinary Scientist) of the Cassini-Huygens mission 
(Titan’s Chemistry and Exobiology program). He is also Co-I (Co-Investigator) of the 
CIRS (Cassini), ACP and GC-MS (Huygens) experiments. He is Co. I of the COSAC and 
COSIMA experiments of the Rosetta European cometary mission. He is Chair of COSPAR 
Commission F (Life Sciences), Vice Chair of COSPAR Planetary Protection Panel and Irst 
Vice-President of ISSOL. He has been member of the Microgravity Advisory Committee 
of the European space Agency and of ESA Exobiology Science Group. He is currently 
member of the Planetary Protection Working Group of ESA. 

He is the author or co-author of more than 200 scientihc papers, and 9 books related to 
the field of the origins of Life and Exobiology. He likes classical music, swimming, tennis 
and mountain climbing by foot in summer and by skis in winter and spring, with his wife 
Florence and his three children Antoine, Stella and Nicolas. 

E-mail: raulin @ 


This volume is a collection of chapters that have been presented as oral presentations or 
posters during the Seventh Trieste Conference on Chemical Evolution and the Origin of 
Life: Life in the Universe — “From Miller Experiments to the Search for Life on Other 
Worlds.” This conference took place at the International Center for Theoretical Physics 
(ICTP), Trieste, Italy on 15-19 September 2003 in Trieste, Italy. 

We were particularly delighted that Professor Miller himself was able to be with us 
for this singular occasion. We all greatly appreciated his retrospective and forward-looking 

The ICTP Center in collaboration with many other institutions has sponsored the previ- 
ous six conferences, since we first started planning the series with Professors Abdus Salam 
and Cyril Ponnamperuma. We were deeply honored, privileged and grateful to have had the 
following 10 sponsors: on this occasion: 

The Abdus Salam International ICTP, Trieste, Italy 
Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy 
Consiglio Nazionale delle Ricerche (CNR), Rome, Italy 
NASA Institute of Astrobiology (NAI), USA 
European Space Agency (ESA), France 
National Aeronautics and Space Administration (NASA) Washington, USA 
University of Paris 12, France 
Osservatorio Astronomico di Trieste, Italy 
Laboratorio dellTmmaginario Scientifico, 

with the collaboration of the book series of 
Kluwer Academic Publishers: 

“Cellular Origin, Life in Extreme Habitats and Astrobiology” 

Among the many presentations that we enjoyed during the conference we had contri- 
butions from experts on questions related to the origin, evolution and cosmic distribution 
of life, as well as talks on cosmology and the origin of biogenic elements and even two 
talks about the destiny of life in the universe from the perspectives of philosophy and 

Aspects of space exploration played a prominent part in our discussions, including 
the Galileo, Cassini-Huygens, Mars Express and Rosetta Missions, as well as proposed 
missions that are currently in the planning stage for Mars and, the Jovian satellite Europa. 
Two additional topics were included to round out our coverage of life in the universe: The 
search for planets outside the solar system, and the closely related subject of the possible 
manifestation of intelligence in potential galactic environments. 

Finally, we continued to dedicate lectures to commemorate Cyril Ponnamperuma and 
Abdus Salam, the two distinguished scientists who initiated this series of conferences. 

We would like to express our pleasure with the wide interest that this conference at- 
tracted. We had worldwide representation from 28 nations, with attendees from: Algeria, 
Argentina, Austria, Brazil, Cameroon, Chile, China, Colombia, Cuba, France, Germany, 
Hungary, India, Iran, Israel, Italy, Mexico, Morocco, Netherlands, Nigeria, Russia, Spain, 
Sweden, Switzerland, Turkey, UK, USA and Venezuela, 



With this conference the Chemical Evolution and the Origin of Life series has now 
brought together well over 500 scientists, philosophers and theologians, since the series 
began in October 1992. It seemed appropriate to remember in particular two members of 
our advisory board, who unfortunately were no longer with us, and whom we remember 
with particular affection for their many solid contributions to the previous meetings: The 
astrophysicist Professor Mayo Greenberg and the biologist Professor Martino Rizzotti. 
They shall remain perennially in our memory. 

February 2004 Joseph Seckbach 

Julian Chela-Flores 
Tobias Owen 
Fran 9 ois Raulin 


We thank all colleagues who assisted us in finishing this volume and made every effort to 
move things along as smoothly as possible. We acknowledge the assistance of Professor 
Mauro Messerotti (Trieste, Italy) for supplying a scientific document, Professor A. Lazcano 
(Mexico City) for assisting with some manuscripts, and Professor Andre Brack (Orleans, 
France) who recommended the source for the hook’s cover. We express our gratitude to 
Make Reimold from the laboratory of Professor von Kiedrowski, Ruhr-University, Bochum, 
Germany, for contributing her artwork to the cover. Last but not least, we appreciate very 
much the great and constant interest of Ms. Claire van Heukelom and Dr. Frans van Dunne 
(Kluwer Academic Publishers) in the series of “Cellular Origins, Life in Extreme Habitats 
and Astrobiology (COLE)’’ books. Their faithful investment in this book is very noticeable. 

Eebruary 2004 Joseph Seckbach 

Julian Chela-Flores 
Tobias Owen 
EranQois Raulin 












10 MILLER, S. 

11 MILLER, D. 

12 MILLER, Miss 

13 OWEN 

14 CHADHA, (Mrs) 













27 Participant 






33 SHAH 





38 MINNITI, Dante 




42 FANI 

43 BRIT 11 

44 FUSI 












56 DICK 





61 Participant 


63 Participant 

64 Participant 


66 Participant 


68a SHIL 



71 Participant 



74a BUSHE 

75 Participant 

76 Participant 


78 Participant 


80 Participant 





85 Participant 


87 PUY 


89 Participant 

90 Participant 

91 UNAK 


“Young Miller” in University of Chicago (1953) 


Photos by NINA ALEXANDRINA (BRAZIL) from “Life in The Universe-2003” Meeting 





I. opening 

“Are we alone?” 


Jet Propulsion Laboratory, California Institute of Technology, 
Pasadena, CA. USA 

Fifty years ago, the Miller experiment took the search for the chemical origins of life to 
a new level with the laboratory synthesis of compounds required for life under conditions 
that resembled the early environment of the Earth. Since that time, scientists from around 
the world have built on these seminal results, developing a multi-disciplinary held that 
explores the fundamental questions of life’s origin and emergence from the outer reaches 
of the universe to the hnest details of microfossils seen in an electron microscope. 

At the Seventh Trieste Conference on the Chemical Evolution and the Origin of Life, over 
one hundred scientists from many countries gathered to discuss and debate the current state 
of knowledge in the held. Highlights included the Cyril Ponnamperuma Lecture by George 
Coyne on Cosmic Evolution, Erank Drake’s pre-dinner talk on the future of SETI, and the 
Abdus Salam Lecture by Stanley Miller himself, rehecting on the history and current state of 
chemical evolution experiments. This volume contains papers describing the research and 
results presented during these deliberations. These papers clearly demonstrate the health 
and vibrancy of the held seen hfty years after the Miller experiment. 

In those hfty years, great advances have been made in many disciplines affecting the 
chemical evolution and origin life. Advances in biology, biochemistry and related helds 
have allowed the exploration of the mechanisms and processes of life at the molecular and 
atomic scale. Astronomical explorations have revealed a universe rich in the building blocks 
of life. Exploration of our own planet has demonstrated that primitive life emerged very early 
in Earth’s history, and we have found life hourishing today under extreme environmental 
conditions previously believed to be completely inimical to any biologic activity. Beyond 
the Earth, reconnaissance of most of the solar system has revealed a remarkable diversity of 
planetary environments, greatly expanding our concept of the ‘habitable zone’ in the solar 
system. Einally, as other planetary systems around distant stars are being discovered at an 
ever-increasing rate, we hnd ourselves asking the question “Are we alone?” in the context 
of new, quantitative information in all these helds. 

The program of the conference featured reviews and new research contributions related 
to all of the above. Looking at the various contributions and listening to the debates from 
my perspective as a planetary scientist, I was struck by several general currents running 
through the proceedings: 

Eirst, the conclusions and insights from the original Miller experiment have proved 
to be remarkably robust. Laboratory equipment and measurement capabilities have vastly 


J. Seckbach et al. (eds.), Life in the Universe, 3 - 5 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


improved in the last fifty years. Ideas about the chemistry of the early Earth’s atmosphere and 
the physics and chemistry of the solar nebula and planet formation have also evolved greatly. 
Nevertheless, the Miller experiment has remained the underpinning for understanding the 
chemical processes leading to the production of biologically interesting compounds, to the 
extent that modern variants of the experiment are still being performed routinely to provide 
samples for comparison with comet surfaces. Titan’s aerosols and interstellar material. 

Second, the search for the earliest evidence for life on Earth illustrates both the tremen- 
dous sensitivity and sophistication of our current technical capabilities but also the frustra- 
tions of trying to wrest unambiguous results from the fragmentary records available to us 
from that early era. Interpretations of claims made on the basis of the fossil record, micro- 
and “nano-” fossils, and blo-markers of various kinds are still being advanced, challenged 
and hotly debated. It is notable that many of these issues arise also in one form or another 
with respect to interpretation of the Martian meteorite results. Clearly, this on-going de- 
bate should make us appropriately cautious and inform our approach to evaluating future 
searches for evidence of extra-terrestrial life. 

Third, the convergence of research on terrestrial life in extreme environments and explo- 
ration of the diverse worlds of our solar system is expanding the range of investigations into 
sites for pre-biotic chemistry and possible habitats for extra-terrestrial life. The following 
are just a sampling of the exciting research areas related to our expanding exploration of 
our local cosmic neighborhood: 

Interstellar dust grains and cometary material have long been regarded as potential windows 
to the original material from which the planets formed and reservoirs of pre-biotic organic 
compounds. The prospects of sample return from the NASA Stardust mission and the ap- 
proaching launch of ESA’s Rosetta promise an exciting new chapter in our understanding of 
these materials. 

Evidence for liquid water flowing on the surface of Mars in past epochs has driven a new 
wave of Mars exploration. Results from NASA’s Odyssey mission have provided maps of 
likely subsurface ice deposits even at low latitudes. During the meeting, the results from past 
missions were reviewed and prospects for future exploration explored. At the time of the 
meeting two NASA rovers and the ESA Mars Express mission with the Beagle 2 lander were 
headed toward Mars. As these proceedings go to press, the Beagle 2 appears to be lost, but 
both Spirit and Opportunity rovers and the Mars Express Orbiter are returning exciting new 
data, beginning a new phase of Mars exploration. 

Other planetary environments of intense interest to the conferees are possible subsurface oceans 
on the icy satellites of the outer solar system. Raised as a theoretical possibility over twenty- 
five years ago, oceans under the icy crusts of Europa, Ganymede and Callisto are strongly 
suggested by a number of lines of evidence from the Galileo mission. Magnetic field data taken 
during close fly-bys of these satellites showed perturbations from induction magnetic fields 
created by the time-varying Jupiter magnetic field (Ganymede also has a large, permanent 
dipole field presumably generated in its core). The best current explanation for this behavior is 
the presence of a global electrically conducting layer near the surface. Rock and ice are poor 
electrical conductors, but saline ocean water would be consistent with the data. 

Europa is particularly interesting because of its geologically young, lightly cratered surface. 
Tidally produced fracture patterns and chaotically disrupted regions reminiscent of melting 


and/or solid-state convective activity in the ice crust suggest that the ocean has been in commu- 
nication with the surface in recent geologic times. Gravitational data suggest a total water plus 
ice thickness of about one hundred kilometers, raising the possibility that this satellite has a 
volume of liquid water in its oceans over twice that in all of Earth’s oceans. NASA is studying 
a future mission, the Jupiter Icy Moons Orbiter, which would return to the Jupiter system and, 
using nuclear ion-drive propulsion, orbit each of the icy satellites and study them in detail. 

Saturn’s large icy satellite Titan is another fascinating world for study of natural organic 
synthesis. With a massive nitrogen/methane atmosphere (surface pressure ~1.5 Earth’s despite 
its low gravity). Titan represents an extraordinary natural laboratory where versions of the 
Miller experiment have been conducted in its atmosphere for perhaps billions of years. Its 
atmosphere rich in hydrocarbons and aerosols and its surface probably a mixture of water ice 
and liquid hydrocarbons. Titan is believed to be an ideal place to study pre-biotic processes and 
compounds. The NASA Cassini mission carrying ESA’s Huygens probe to Titan will arrive at 
Saturn in July 2004, and Titan will one of the major targets of its projected four-year mission 
of exploration. 

Finally, the discovery of extra-solar planetary systems around other stars has added a 
new dimension to the discussions of life in the universe. Discussions at the conference 
ranged from the nature of these systems and the types of environments for life they might 
harbor to methods of detecting the presence of life by remote observations of these systems. 
It is clear that we are now only looking at the hrst hints of what will be in the future a large, 
exciting field of study. 

The discussions of this Trieste Conference and the papers in this volume represent a 
“snap-shot” of the status of our understanding of the chemical evolution of life and the 
current issues related to life in the universe - fifty years beyond the Miller experiment and 
at the opening of the next century of exploration. We can only speculate about and eagerly 
anticipate the advances the next fifty years may bring. 



Department of Biochemistry and Biophysics, Arrhenius Laboratories, 
Stockholm University, S-106 91 Stockholm, Sweden. 

Professor Stanley Miller, Professor K. R. Srinivasan, Organizers and Sponsors 
of this Conference, Ladies and Gentlemen; 

We are getting ready for the Abdus Salam Lecture, honoring two most distinguished scien- 
tists. Both have very significantly contributed to the rapid growth of the sphere of funda- 
mental knowledge in the second half of the twentieth century. 

Abdus Salam, theoretical physicist, Nobel Prize winner, creator and long time leader 
of The Abdus Salam Center of Theoretical Physics. With his active interest in the origin 
of life he played a leading role in instigating these conferences on Chemical Evolution and 
the Origin of Life here in Trieste, which still are of such primary importance in this field. 
He left this world in 1996. 

And Stanley Miller, who most generously, as the Abdus Salam Lecturer, is going to 
give us his “Recollections of the beginning of chemical evolution experiments”: 

Dear Stanley, it is a great privilege, and indeed a pleasure to introduce you. This is in a 
way a quite easy task, because we all already know that “the Miller experiment”, which is 
most appropriately placed in the title of this conference, in 1953, exactly 50 years ago, was 
a major breakthrough, opening up a new research field with, and for, rational and advanced 
chemical experimentation on the molecular origin of life. 

It would take too much time to try to describe here your scientific carrier, your prices, 
your Presidency of ISSOL and your many other successes. So I rather will end this intro- 
duction with a couple of personal recollections. 

First I would like to combine something of Abdus Salam and Stanley Miller. Abdus 
Salam gave the very first invited lecture of the University of Stockholm International Lec- 
tures on Human, Global and Universal Problems, in 1975. And 10 years later, at Lidingo 
close to Stockholm, Stanley Miller gave the opening lecture of a conference on the Molec- 
ular Evolution of Life. On a picture I took, as a co-arranger of these events, Stanley is seen 
approaching in his usual, modest way, more focussed on scientific discussion than on the 

Last but not least, I shall tell you the true story about when we learned that Stanley 
is an enthusiastic environmentalist, in the best sense of the word. About 25 years ago, in 
Stockholm, Stanley, my wife and I strolled in the King’s Garden. Its elmtrees were full 


J. Seckbach et al. (eds.), Life in the Universe, 7 - 8 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 

of young people who, some even spending nights in the trees, prevented the authorities 
from removing the elmtrees, hy ax and saw. Also Stanley signed a petition to save the 
elmtrees — and they were saved! 

Stanley, I believe that your greatness as a scientist and as a friend must be linked 
to the many facets of your wonderful personality. We much look forward to your 

Recollections and Perspectives 


^Department of Chemistry and Biochemistry University of California, San 
Diego 9500 Gilman Dr La Jolla, CA, USA, ^Scripps Institution of 
Oceanography University of California at San Diego La Jolla, CA 
92093-0212, USA, ^Facultadde Ciencias, UNAM Apdo. Postal 70-407 Cd. 
Universitaria, 04510 Mexico D.F. Mexico. 

I. Introduction 

In spite of the ongoing debate about the oldest morphological evidence of life, it is generally 
accepted by scientists that the first living beings emerged on Earth early in the history of 
the planet. However, our understanding of the processes that led to the emergence of life 
is also hindered by the lack of geological evidence of the prebiotic environment, i.e., we 
have no direct information on the chemical composition of the primitive atmosphere, the 
temperature of the planet, the pH of the primitive hydrosphere, and other conditions which 
may have been important for the origin of life. Hence, it is not surprising that this has led 
to intense debates and the formulation of different and even contradictory explanations of 
how life came into being. 

This situation is not new. Since the late 19th century, the belief in a natural origin 
of life had become widespread, and few years afterwards many attempts had been made 
by prominent scientists to explain the origin of life. As reviewed elsewhere (Miller et ah, 
1997), the list covers a rather wide range of explanations that include Pfliigger’s ideas 
on the role of HCN, to those of Svante Arrhenius on panspermia, and include Leonard 
Troland’s hypothesis of a primordial enzyme formed by chance events in the early oceans, 
the sulfocyanic theory of the autotrophic origin of the protoplasm developed by Alfonso L. 
Herrera, and Herman Muller’s proposal of the abrupt formation of a mutable gene endowed 
with hetero- and autocatalytic properties. In spite of the diversity of these concepts, most of 
them went unnoticed, in part because each was incomplete and speculative, unsubstantiated 
by direct evidence, and not subject to empirical investigation. 

Although it is true that many scientists favored the idea of primordial beings en- 
dowed with a plant-like, autotrophic metabolism that could allow them to use CO 2 as 
their source of cellular carbon, others like A. I. Oparin, J. B. S. Haldane, C. B. Lipman, 
and R. B. Harvey proposed independently an heterotrophic origin of life, required the 
synthesis of simple organic compounds by various processes. The most successful and 
best-known proposal was that by Oparin, who, from a Darwinian analysis, proposed a se- 
ries of events from the synthesis and accumulation of organic compounds to primordial 


J. Seckbach et al. (eds.), Life in the Universe, 9 - 16 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


life forms whose maintenance and reproduction depended on external sources of reduced 

The assumption of an abiotic origin of organic compounds rested on firm grounds. In 
1824 Wohler has achieved the chemical synthesis of urea and oxalic acid from inorganic 
starting materials, and in 1828 he was able to confirm the identification of urea formed from 
silver cyanide and ammonium chloride. In fact, many of the reactions previously studied by 
organic chemists have turned out to be important primitive Earth synthesis, including the 
laboratory synthesis of alanine achieved by Strecker in 1 850 from a mixture of acetaldehyde, 
ammonia, and hydrogen cyanide, and the formation of sugars from formaldehyde under 
strong alkaline conditions reported by Butlerow in 1861 (Bada and Lazcano, 2003). These 
efforts in fact heralded the era of organic chemistry but, as discussed elsewhere (Lazcano 
and Bada, 2003), the motivation of such studies was to synthesize organic compounds 
and not to understand what happened on the primitive Earth. The first successful prebiotic 
experiments in support of Oparin’s ideas came first from the laboratory of Harold C. Urey’s in 
the University of Chicago in 1953, and here we discuss come these experiments came about. 

2. A Laboratory Model of the Primitive Earth 

Erom the 1950s, chemists were drawn toward the origin of life. Driven by his interest in 
evolutionary biology, Melvin Calvin and his collaborators at the University of California, 
Berkeley, attempted to study the possibility of organic compounds under primitive Earth 
conditions with high-energy radiation sources. They irradiated a gas mixture of CO 2 , H 2 O, 
H 2 and a solution of Fe^+ with 40-meV helium ions using the Crocker Laboratory’s 60-inch 
cyclotron (Garrison et al., 1951). The results, however, were not encouraging: only small 
amounts of formic acid and formaldehyde were obtained, which is similar to results obtained 
in experiments done since the 1920s by several other researchers attempting to understand 
the chemical mechanisms underlying photosynthetic processes (Rabinowith, 1945). 

In 1950 the Nobel laureate Harold C. Urey, who had been involved with the study of 
the origin of the solar system and the chemical events associated with this process, began 
to consider the origin of life in the context of his proposal of a highly reducing terrestrial 
atmosphere. Urey presented his ideas during a seminar at the University of Chicago in 
October of 1951. In his lecture Urey pointed out that the solar system is reducing (that is, 
there is an excess of molecular hydrogen), except for the Earth and the minor planets (Mars, 
Venus and Mercury), which are more oxidized, with the terrestrial atmosphere being highly 
oxidized. According to Urey, a reducing atmosphere would contain methane, ammonia, 
water, and molecular hydrogen, as found on Jupiter and Saturn (except that the water has 
been frozen out) and on Uranus and Neptune, where both the water and ammonia have 
been frozen out. Urey thought that such type of reducing atmosphere would be a favorable 
place to synthesize organic compounds, which would form the basis to make the first living 
organism on Earth. It was only after this seminar that a biochemjist brought Oparin’s book to 
Urey attention, pointing out how Oparin had discussed the origin of life and the possibility of 
synthesis of organic compounds in a reducing atmosphere. Urey of course acknowledged 
Oparin’s contributions in a paper he published one year later detailing his model of the 
primitive atmosphere (Urey, 1952). 

The electric discharge experiment followed shortly after (Miller, 1953). In September 
1952, almost a year and a half after attending Urey’s seminar, one ofus(S.L.M.) approached 


E pctmdK 

Figure 1. The various apparatus used in the Miller experiment (see text for explanation). 

him about the possibility of doing a prebiotic synthesis experiment as a doctoral thesis topic. 
The issue was not just how to synthesize organic molecules under primitive terrestrial 
conditions, it was the first step in understanding how life started on our planet. Urey’s initial 
resistance to this project was outdone after agreeing to try the organic compound synthesis 
for six months or a year. If nothing came of the project by this time, then a different, more 
conventional thesis project would be undertaken. 

After realizing that ultraviolet light and electric discharges must have been the most 
abundant energy sources on the primitive Earth, and that very little work had been done 
on the effect of electric discharges on mixtures of methane and nitrogen or oxygen-bearing 
compounds, it was decided that amino acids were the best group of compounds to look 
for first, since they are the building blocks of proteins and since the analytical methods for 
their detection were at that time relatively well developed. Three spark discharge different 
apparatus to be used in the experiment where then designed (Figure 1). They were meant to 
simulate the ocean-atmosphere system on the primitive Earth, containing a model ocean, an 


atmosphere, and a condenser to produce the rain. Water vapor produced by heating would be 
like evaporation from the oceans, and as it mixed with methane, ammonia, and hydrogen, 
it would mimic a water vapor-saturated primitive atmosphere. The apparatus shown in 
Figures la and lb was the one most extensively used in the original experiments, and is 
the design most widely known today. The apparatus Ic led to a higher inner pressure, and 
an important aspect of its design is that it generates a hot water mist that could be consider 
similar to a water vapor- rich volcanic eruption. The apparatus shown in Figure Id used 
a so-called silent discharge instead of a spark, a concept that had been used previously 
in attempts to make organic compounds from CO 2 in order to understand the nature of 
photosynthesis (Lazcano and Bada, 1953). 

3. The Prebiotic Chemistry of Amino Acids 

Results were produced almost as soon as the experiments were begun in the fall of 1952. 
After filling the apparatus with the postulated primitive atmosphere of water, methane, 
ammonia, and hydrogen, the spark was turned on, and after two days the solution was a pale 
yellow. The solution was concentrated, and after running a paper chromatogram, a small 
purple spot was found which upon spraying with ninhydrin was shown to be moving at the 
same rate as glycine. 

It was decided to repeat the experiment one more time, sparking the mixture for a whole 
week. After the first night the solution looked distinctly pink, and as the sparking continued 
it became first a deeper red and then a yellow-brown which obscured somewhat the red 
color (Miller, 1953). After the week of sparking the inside of the upper flask was coated 
with an oily material and the water had a yellow-brown color. Contrary to some original 
speculations, the red color observed the first day turned out not to be porphyrins (Miller, 
1974), and was not observed when the apparatus was rebuilt, probably because the Pyrex 
glass of the first apparatus was particularly rich in trace elements. However, the search for 
amino acids was very successful. When paper chromatography was used to characterize 
the compounds that had formed, spraying with ninhydrin showed that the glycine spot was 
much more intense and spots corresponding to several other amino acids were also detected 
(Miller, 1974). Three of these amino acids were strong enough and in the correct position 
to be identified as glycine, a-alanine, and (3-alanine. Two spots were considerable weaker 
in color but corresponded to aspartic acid and a-amino-n-butyric acid. The two remaining 
spots did not correspond to any of the amino acids that occur in proteins or any known amino 
acids then available, so they were simply labeled as A and B (Figure 2). It was estimated 
that at least 10 mg of amino acids had been formed, and it was concluded that the total yield 
was in the milligram range (Miller, 1953). Experiments with the apparatus in Figure la and 
lb, as well as the one in Figure Ic produced in general a similar distribution and quantities 
of amino acids and other organic compounds. In contrast, experiments with the apparatus 
in Figure Id led to lower overall yields and a much more limited suite of amino acids: 
essentially only sarcosine and glycine were produced (Miller, 1955). 

After discussing the outcome of the experiment with Urey, it was decided to have its 
results published as soon as possible. A short manuscript was thus prepared, but in a very 
generous way Urey decided not to be included as a coauthor, in recognition of the work done 
largely by S. L Miller. The paper was first sent to Science on February 1952, but after some 


PHENOL 10.3% 

(2) y. 

I ® © ' 


Figure 2. The two dimensional paper chromatogram of the amino acids produced from the sparking experiment 
(Miller, 1953). 

delay and confusion it was retired and submitted to the Journal of the American Chemical 
Society, only to be retired and resubmitted to Science, where it was published on May 1953 
(Lazcano and Bada, 2003). 

Although by comparison with contemporary analytical tools the methods available in the 
early 1950s were crude, the search for amino acids was very thorough in terms of the tech- 
niques then available. These included the determination of the melting points of the amino 
acids that had been synthesized, which was at the time the usual method of positively iden- 
tifying organic compounds. This represented several months work, but the identifications 
were then firmly established and have not been disputed ever since. Equally important, the 
possibility of biological contamination was completely ruled out by autoclaving the appara- 
tus, which had been filled wifh fhe mixfure of reduced gases, for 18 hours. The experimenf 
was repeafed and fhe yield of amino acids was fhe same as fhe runs where fhe apparafus 
was not autoclaved (Miller, 1974). 

4. The Dawn of Organic Chemistry and Prebiotic Syntheses 

It is not strictly correct to say that the 1953 Miller experiments were the first organic com- 
pound synthesis under primitive Earth conditions, since many of the reactions previously 
studied by organic chemists have turned out to be important primitive Earth synthetic reac- 
tions (Miller, 1974). In 1824 Eriedrich Wohler reported that the reaction of cyanogen with 
ammonia solution led, in addition to several other products, to oxalic acid and “a crystalline, 
white substance” which was properly identified as urea four years lafer (Wohler, 1828). As 
reviewed elsewhere (Bada and Lazcano, 2003), alfhough it was not immediately recognized 
as such, a new era in chemical research had begun: in 1850 Adolph Strecker achieved the 
laboratory synthesis of alanine from a mixture of acetaldehyde, ammonia, and hydrogen 
cyanide, and in 1861 Alexandr M. Butlerov showed that the treatment of formaldehyde 
with strong alkaline catalysts, such as sodium hydroxide (NaOH), leads to the synthesis of 
a wide array of sugars. 


Research on the laboratory synthesis of biochemical compounds was soon extended to 
include more complex experimental settings. Towards the end of the 19th century a large 
amount of research on organic synthesis had been done, and had led to the abiotic forma- 
tion of fatty acids and carbohydrates using electric discharges with various gas mixtures 
(Rabinovitch, 1945). As summarized elsewhere, this line of research was continued into 
the 20th century by Klages (1903), Ling and Nanji (1922), and Herrera. (1942) Moreover, 
Walter Lob, Oskar Baudish and others worked on the synthesis of amino acids by exposing 
wet formamide (CHO-NH 2 ) to silent electrical discharges (Lob, 1913) and to UV light 
(Baudish, 1913). 

As discussed elsewhere (Bada and Lazcano, 2002), Lob did indeed report the synthesis 
of glycine by exposing wet formamide to a silent discharge. He suggested that because of 
either the ultraviolet light or the electric field generated by the silent discharge, formamide 
is first converted to oxamic acid, which in turn is reduced to glycine. He also claimed 
that glycine is produced when wet carbon monoxide and ammonia are subject to the silent 
discharge, and proposed formamide as the intermediate in this synthesis. Lob also theorized 
that glycine might also be produced from wet carbon dioxide and ammonia in a pathway 
wherein formamide was again the intermediate, but he did not demonstrate this directly. 
Although Lob apparently did produce glycine from formamide, this cannot be considered a 
prebiotic reaction because formamide would not have been present on the primitive Earth in 
any significant concentrations. It is also possible that the wet carbon monoxide and ammonia 
led to the synthesis of HCN, which would have produced glycine on polymerization and 
hydrolysis (Lazcano and Bada, 2003). 

In retrospect, the efforts by Wohler, Strecker, Butlerov, Klages, Lob and others to produce 
simple organic compounds from simple reagents heralded the dawn of prebiotic chemistry, 
and have some bearing on our understanding of prebiological evolution. However, there 
is no indication that Lob and the others who carried out these studies were interested in 
how life began in Earth, or in the synthesis of organic compounds under possible prebiotic 
conditions. This is not surprising; since it was generally assumed that the first living beings 
had been autotrophic, plant-like microbes, the abiotic synthesis and accumulation of organic 
compounds was not considered to be a necessary prerequisite for the emergence of life. In 
fact, these experiments were not conceived as laboratory simulations of Darwin’s warm little 
pond, but rather as chemical models designed to understand the autotrophic mechanisms of 
nitrogen assimilation and CO 2 fixation in green plants (Bada and Lazcano, 2002). 

5. Afterword 

The lack of direct geological evidence of the environmental conditions of the primitive 
Earth at the time life emerged always raises the question of whether the spark discharge 
experiments and other laboratory simulations are an adequate model of the primitive Earth. 
Contemporary geoscientists tend to tend to doubt that the primitive atmosphere had the 
highly reducing atmosphere modeled in the original Miller experiment. One additional 
objection would be that the input of electrical energy was far higher than possible in the 
primitive atmosphere. However, a striking confirmation of the general validity of this ex- 
perimental simulations came from the analysis of the Murchison meteorite, which fell 
in Australia on September 29, 1969. This meteorite was shown to be a carbonaceous 


chondrite that was particularly rich in organic compounds, including a wide array of indige- 
nous amino acids. The amino acids first reported in the Murchison meteorite were glycine, 
alanine, sarcosine, glutamic acid, and a-aminoisobutyric (Ring et al., 1972), all of which 
had been found in the original electric discharge experiment (Miller, 1953), as well as valine 
and proline. A second paper on amino acids in Murchison reported the presence of N-methyl 
alanine, (3-alanine, aspartic acid, and a-amino-n-butyric acid (Wolamn et al., 1972). Al- 
though a number of amino acids have been reported in the Murchison had not been found 
in the electric discharge experiment, the meteorite contained most of those formed in the 
1953 Miller experiment. Thus, although there is no geological evidence for the existence of 
Oparin’s postulated prebiotic soup, the occurrence of amino acids, as well as purines, pyrim- 
idines, sugar derivatives, and many other compounds in the 4.6 x 10® years-old Murchison 
meteorite makes it plausible (but does not prove) that similar abiotic synthesis took place 
on the primitive Earth. 

Many have suggested that the organic compounds needed for the appearance of life may 
have originated from extraterrestrials sources such as meteorites. It is of course unlikely that 
a single mechanism can account for the wide range of organic molecules that may have been 
present in the prebiotic Earth. Rather, the primitive soup was almost certainly formed by 
contributions from endogenous and exogenous sources — from local synthesis in reducing 
environments, and on metal sulfides at deep-sea vents, as well as from comets, meteorites 
and interplanetary dust. This eclectic view does not beg the issue of the relative significance 
of the different contributors of organic compounds: it simply recognizes the wide variety 
of potential sources of the raw material required for the origin of life. 

The existence of diverse non-biological mechanisms by which biochemically relevant 
monomers can be synthesized under plausible prebiotic conditions is now established. Of 
course, not all prebiotic pathways are equally efficient, but the wide range of experimental 
conditions under which organic compounds can be synthesized demonstrates that prebiotic 
syntheses of the building blocks of life are robust. The abiotic reactions producing such 
compounds span a broad range of seetings, and are not limited to a narrow spectrum 
of highly selective reaction conditions. Our ideas on the prebiotic formation of organic 
compounds are largely based on experiments in model systems. How life arose on Earth is 
of course unknown, but it is certainly encouraging to see that we have reached this level of 
understanding of the chemistry of the prebiotic Earth 50 years after the electric discharge 
experiments simulating the primitive environment were first performed. 

6. Acknowledgements 

Eor grant support, we thank the NASA Specialized Center of Research and Training 
(NSCORT, UCSD) (S.L.M, J.L.B, A.L.) and UNAM-DGAPA Proyecto PAPIIT IN 1 1 1003- 
3 (A.L.). 

7. References 

Bada, J. L. and Lazcano, A. (2002) Miller revealed new ways to study the origin of life. Nature 416, 475. 
Bada, J. L. and Lazcano, A. (2003) Prebiotic soup — revisiting the Miller experiment. Science 300, 745-746. 


Baudish, O. (1913) Ueber das CO 2 fixation. Angew. Chem. 2, 612-616. 

Garrison, W. M., Morrison, D. C., Hamilton, J. G., Benson, A. A., and Calvin, M. (1951) The reduction of carbon 
dioxide in aqueous solutions by ionizing radiation. Science 114 , 416^18. 

Herrera, A. L. (1942) A new theory of the origin and nature of life. Science 96 , 14. 

Klages, A. (1903) Ueber das methilamino-acetonitril. Berichte der Deutschen Chemischen Gesellschaft 36 , 1506. 

Lazcano, A. and Bada, J. L. (2003) The 1953 Stanley L. Miller experiment: fifty years of prebiotic organic 
chemistry. Origins Life Evol. Biosph. 33, 235-242. 

Ling, A. R. and Nanji, D. R. (1922) The synthesis of glycine from formaldehyde. Biochem. J. 16 , 702-705. 

Lob, W. (1913) Uber das Verhalten des Formamids unter der Wirkung des stillen Entladung. Ein Beilrag zur Frage 
der Stickstoff- Assimilation. Bercfihte der Deutschen Chemischen Gesellschaft 46 , 684-697. 

Miller, S. L. (1953) A production of amino acids under possible primitive Earth conditions. Science 117 , 528-529. 

Miller, S. L. (1955) Production of some organic compounds under possible primitive Earth conditions. J. Am. 
Chem. Soc. 77, 2351-2361. 

Miller, S. L. (1974) The first laboratory synthesis of organic compounds under primitive Earth conditions. In 
Jerzy Neyman (ed.). The Heritage of Copernicus: theories “pleasing to the mind” (MIT Press, Cambridge), 

Miller, S. L., Schopf, J. W., and Lazcano, A. (1997) Oparin’s “Origin of Life”: sixty years later. J. Mol. Evol. 44 , 

Rabinovich, E. I. (1945) Photosynthesis. Vol I (Interscience, New York), pp. 61-98. 

Ring, D., Wolman, Y, Friedmann, N., and Miller, S. L. (1972) Prebiotic synthesis of hydrophobic and protein 
amino acids. Proc. Natl. Acad. Sci. USA 69 , 765-768. 

Urey, H. C. (1952) On the early chemical history of the Earth and the origin of life. Proc. Natl. Acad. Sci. USA 
38, 351-363. 

Wohler, F. (1828) Ueber das organische synthese. Ann. Physik 12 , 253. 

Wolman, Y, Haverland, W. J., and Miller, S. L. (1972) Nonprotein amino acids from spark discharges and their 
comparison with the Murchison meteorite amino acids. Proc. Natl. Acad. Sci. USA 69 , 923-926. 



Specola Vaticana, V-00120 Citta del Vaticano Rome, Italy 

Abstract. Since chemical complexity and then life itself came about as part of the evolution- 
ary history of the cosmos, it would be helpful to have an overview of that history. After an 
introduction to a few key concepts, several relevant topics in modem cosmology are reviewed. 
These include: the Hubble Law and the age of the universe; large scale stmcturing; galaxy 
formation and evolution; and cosmic chemistry. 

I. Key Concepts 

A preliminary time scale for the evolution of the universe is basic to our discussion. If we 
take the age of the universe as of the order of 10^* secs (we will refine this shortly) then 
the universe became transparent, the decoupling of radiation from matter, at 10'^ secs. The 
Planck time is measured as 10“"^^ secs and inflation, of which we will speak shortly, occurred 
shortly after the Planck time. In the intervening period, from inflation to the present, stars 
and galaxies formed, structure in the radiating and non-radiating material developed and 
we came to be. 

Cosmological distances are typically expressed as a measure of the redshift, z. The 
relationship between distance and redshift requires a cosmological model which gives the 
fundamental constants of the expanding universe. It is usual to adopt the Standard Model 
(Longair, 1996). Thus, at z = 0. 1 the distance is approximately 1 .5 x 10® light years, at z = 

I. 0, about 9 X 10® light years and at z = 10, about 13 x 10® light years. When cosmologists 
refer to “high redshift galaxies” they mean those with redshifts greater than z — 0.1. The 
most distant galaxies yet detected have redshifts of about z = 6.5. 

When cosmologists say that the universe is “flat”, they mean that in its expansion it is just 
on the edge of expanding forever or collapsing in upon itself. Among all the possibilities 
for the expansion rate of the universe, it is remarkable that it is “flat” and this requires 
explanation. In 1980 Alan Guth (Guth and Tye, 1980) first proposed that the universe 
inflated at many times the velocity of light very shortly after the Planck time. The energy 
source is found in quantum mechanical phase transitions in the early universe before there 
was matter, so that velocities exceeding that of light could occur. A schematic presentation 
is given in Fig. 1 . In a non-inflationary universe, depicted at the top, when the universe was 
at t = 10“^^ sec it had a radius of 1 mm, which is much larger than the horizon distance of the 
universe at that time. With expansion the horizon of the visible universe is at a distance of 
10^^ cm (based on an age for the universe of 13.7 x 10® years). In an inflationary universe, 
depicted at the bottom, the universe inflated so that at t = 10“^^ sec it had a radius of 


J. Seckbach et al. (eds.), Life in the Universe, 17 — 26 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. A schema of a non-inflationary (a) and an inflationary universe (b) 

3x10^^ cm. Thus today it has dimensions which are much larger than the horizon distance 
of 10^* cm, the distance which light can travel in the total age of the universe. Our visible 
universe is, therefore, inserted in a “multi-verse” invisible to us. This, of course, raises 
the question of the verihability or falsifiability of such a multi-verse. However, the hrst 
predictions of observational tests of inflationary cosmologies are now being made (Hogan, 

2. The Hubble Law Revisited and the Age of the Universe 

One of the most fundamental ways of measuring the age of the universe is to determine 
its expansion rate, the velocity of expansion with distance, and thus calculate when the 
expansion began. This is called the “Hubble Law” and it is illustrated in Fig. 2 where 
the velocity in kilometers per second is plotted against distance measured in millions of 


parsecs (one parsec equals 3.26 light years). The slope of this relationship, the Hubble 
constant Hq, is inversely proportional to the time when the expansion began and thus to the 
age of the universe. The best ht to the observations (dots) is Hq = 67 km/sec/megaparsec; 
extreme values of Hq are also shown. The scatter in the observations, which increases with 
distance, reveals serious difficulties involved in obtaining accurate measurements both of the 
velocities and of the distances. In fact, measuring velocities is quite straight forward since 
it simply involves measuring the shift in wavelength of spectral lines in celestial objects, 
Doppler shift or redshift. But it is the selection of the objects and the interpretation of the 
measurements that create difficulties. What one wishes to measure is the expansion in the 
space-time structure of the universe, the so-called “Hubble flow.” To do this one must select 
objects that are participating in that expansion. This typically means measuring the redshifts 
of galaxies and clusters of galaxies. However, galaxies have their own peculiar motions in 
addition to their motion with the Hubble flow and clusters of galaxies have the peculiar 
motions of their member galaxies and the peculiar motion of the cluster as a whole. These 
difficulties are best overcome by measurements made for objects at very large distances 
where the expansion velocities are very large, so that peculiar velocities are an insignificant 
fraction of the total velocities measured. But then the difficulty arises in the measurement 
of distances, since the error in the distance measurement increases with distance. In fact, 
the whole case for getting an accurate measurement of the Hubble constant comes down to 
measuring astronomical distances. Even with telescopes in space, outside the perturbations 
of the earth’s atmosphere, geometrical determinations of distances are accurate to only 
about 3,000 light years, three percent of the diameter of the Milky Way. The usual way to 
proceed beyond is to use the so-called photometric distance measurements, whereby we 


assume the existence of “standard candles” in the universe, classes of objects that have the 
same intrinsic luminosity, so that their measured apparent luminosity is the result of only 
the inverse square distance for light propagation. Hubble, for instance, first measured the 
distance to the Andromeda nebula by using Cepheid variable stars as a standard candle. In 
order, however, to measure to very large distances we need objects which are intrinsically 
very bright. In recent years use has been made of type la supernovae (Saha et al., 2001; 
Sandage, 2002). The progenitors of these supernovae are binary white dwarfs wherein mass 
exchange causes a nuclear explosion. It is remarkable that the peak brightness in these 
systems is quite constant considering the origins of the energy and the fact that each system 
results in the nucleosynthesis of different amounts of certain isotopes, for instance Ni^®. 
Recently three other non-photometric methods have been used to measure large distances: 
measurements of the size and optical depth of holes in the cosmic background radiation 
(CBR) due to the Sunyaev-Zeldovich effect, gravitational lensing and fluctuations at high 
resolution in the CBR. Gravitational lensing is of particular interest since it allows the 
rather accurate determination to a lensed galaxy at a very large distance. Cardone et al. 
(2002) have made a determination of the Hubble constant by the measurement of the time 
delays in the arrival of the four images from a distant galaxy. Since there are more than 
50 multiply imaged systems known this promises to be an excellent way to obtain an 
independent measure of the Hubble constant. The result of all of the tedious measurements 
described above is a Hubble constant which translates into an age of 1 3.7 x 10® years for the 

3. Large Scale Structure. Clustering and Voids 

Why is it important to know the large scale distribution of matter in the universe? The distri- 
bution of matter today is the inheritance of the fluctuations in the early universe, propagated 
to the current epoch according to a given world model, i.e. the fundamental parameters 
of the universe: deceleration or acceleration, matter and energy densities, including dark 
matter and dark energy, etc. So the large scale distribution of matter will be a test of how 
well we know those fundamental parameters. Since galaxies are the luminous tracers of 
the way matter is distributed, it is important to map the distribution of galaxies to large 
distances. Hubble Space Telescope has observed rich clusters of galaxies, containing thou- 
sands of galaxies, out to distances of 8 x 10® light years. The first large galaxy redshift 
survey was conducted at the Harvard-Smithsonian Center for Astrophysics in the 1980s 
(Geller, 1990). That survey plotted 1,065 galaxies in a slice of the universe whose outer 
edge was at 450 million light years. Later about 10,000 additional galaxies were measured. 
This survey already began to reveal the so-called “soap bubble” structure with large clumps 
of galaxies and large voids. In recent years large automated sky surveys have already mea- 
sured redshifts for hundreds of thousands of galaxies. At the Anglo- Australian Observatory 
the Two-Degree Field (2dF) Galaxy Redshift Survey was completed in April 2002 (Colless, 
2003). It plotted more than 200,000 galaxies out to distances of 3 x 10® light years and con- 
firmed the soap bubble structure of the universe to larger distances. A detailed comparison 
of the galaxy distribution with the small scale temperature fluctuations in the CBR showed 
that the distribution of visible mass (galaxies) is an excellent tracer of the over all mass of 
the universe (including dark matter). It also confirmed that some unknown form of dark 


energy is the dominant constituent of the universe and is causing the universe to accelerate 
in its expansion. An even more ambitious survey, The Sloan Digital Sky Survey (SDSS), an 
international collaboration, is under way and will be completed in June 2005. It will have 
measured redshifts for 600,000 galaxies in addition to positions and 5 -color photometry for 
100 million celestial objects (mostly galaxies) over 6,600 square degrees or one-sixth of 
the sky (Frieman and SubbaRao, 2003). 

What is the largest scale on which clustering of galaxies and voids occur? Flow does one 
determine this? The apparent sizes must be corrected for inaccuracies in distance determi- 
nations. For instance, galaxies that appear to be at the edge of a void may be foreground or 
background objects to the actual void. Statistical methods have been developed for “walk- 
ing around” the edges of an apparent void and determining its actual diameter (Hoyle and 
Vogeley, 2002). The result is that the largest voids measure about 150 million light years 
in diameter, about 1500 times the diameter of the Milky Way. This result is confirmed by a 
detailed study of the 2dF Survey mentioned above (Roukema, Mamon and Bajtlik, 2002). 
A surprising result has been that intergalactic clouds have been found statistically to be as 
common within voids as elsewhere (Manning 2002). These clouds are discovered by the 
so-called “Lyman-alpha forest,” a series of Lyman-alpha absorption lines of the light from 
distant quasars shifted into the visual spectral regions by the Hubble flow. These clouds 
may be either proto-galactic, galaxies in formation, or simply the dissipation of a gas cloud 
which failed to form a galaxy. At any rate voids are apparently not altogether empty! 

An important issue is the change in structure with distance and thus with time since 
the Big Bang. The problem here is that there are two effects which tend to cancel out each 
other. Any clustering that begins will generally increase with time. That is the way gravity 
works. So we should see more clustering nearby. But as we observe to greater distances we 
preferentially see the more clustered arrays, since they are the brightest and more obvious. 
The surveys mentioned have not yet succeeded in separating out these two effects and 
providing an answer to the development of structure with time in the expanding universe. 

4. Galaxy Formation and Evolution. The Rate of Star Formation 

Did the nuclei of galaxies form first and then by their gravity assemble stars already formed 
elsewhere? Or did stars form within a galaxy as the nucleus and other galactic features were 
also forming. The most likely answer is both with one or other scenario dominating in certain 
types of galaxies. One model of interest starts with the collapse of a 10'° solar mass cloud 
at about 12 x 10® years ago, just 1.7 x 10® years after the Big Bang (Mangalam, 2001). 
As a core forms the first generation of massive stars also forms. Thus enriched material 
is supplied to a rotational disk which forms after 0.5 x 10® years from the beginning of 
the cloud collapse. Stars continue to form in this disk, a second generation from material 
enriched by supernovae from the first generation, and the core continues to collapse to from 
a black hole of 10® solar masses. The only reason that star formation can continue is that 
the supernovae heat energy is less than the binding energy or that the cooling time of the 
hot gas is less than the time to escape the halo. At the end of this process we have a black 
hole nucleus, a bulge, a halo and a disk in which star formation continues. These structures 
are typical for galaxies as we observe them, varying in how much one or other structure 
dominates in different galaxy types: elliptical, spiral, irregular, etc. 


Figure 3. The rate of star formation is plotted as a function of “look back time” for: observations in the 
ultraviolet to submillimeter wavelength range (solid line); for gamma-ray bursters interpreted as “collapsers” 
(histograms to the lower right); for gamma-ray bursters interpreted as “mergers” (histograms to the upper 
right). See text for further explanation. 

Since one of the principal reasons for the difference in galaxy types is the rate of star 
formation, it is important for an understanding of galaxy evolution to study star forma- 
tion rates as a function of redshift or “look hack time” in the expanding universe. A best 
representation using data from the ultraviolet to submillimeter wavelengths is shown by 
the solid line in Fig. 3 (Blaine 2001) where the star formation rate, p(z), normalized to 
z = 1.5, is plotted against 1 + z. The maximum rate occurs at a look back time of about 
10 X 10® years, 3.7 x 10® years after the Big Bang. However, there is almost certainly an 
undersampling at large distances where only very intrinsically bright objects can be seen at 
the wavelengths covered. For this reason an interesting attempt has been made to sample 
star formation by using gamma-ray bursts, since these are very energetic events both in 
gamma-rays and in the associated optical transient emission and since their progenitors are 
thought to be short lived massive stars (Lloyd-Ronning et ah, 2002). The results of this 
study of 220 gamma-ray bursts is shown by the four histograms in Fig. 3. It is thought that 
gamma-ray bursts arise from either the mergers of massive stellar remnants (neutron stars 
and black holes; Paczyhski 1986) or from the collapse of massive stellar cores (hypernovae, 
Paczyhski 1998). In either case they apparently help us to sample massive star formation 
at early epochs. In Fig. 3 the two histograms extending to the bottom right are derived by 


considering the collapse model and those rising to the right top hy considering the merger 
model. In each case the difference between the two histograms is of no significance to our 
discussion, since it considers the flatness of the initial mass function which is not of concern 
to us now. It is clear, however, that, whatever the interpretation of the massive progenitors of 
gamma-ray bursts, massive stars formed in the very early epochs of the universe, as early as 
0.5 X 10® years after the Big Bang. This could not be determined by observations in the uv 
to submillimeter wave range (solid curve in Fig. 3). The universe was developing structure: 
stars, galaxies, even clustering, at a much earlier epoch than had been thought possible a 
few years ago. 

5. Cosmic Chemistry 

All chemicals, except for the lightest elements, come from nucleosynthesis in stars. In the 
very early hot universe hydrogen, deuterium, helium and a few other light elements were 
made, but, as the universe expanded and cooled down, hot spots which housed thermonu- 
clear furnaces were required to generate the heavier elements. With the passage of each 
generation of stars the universe became more metal abundant. The heaviest elements come 
from supernovae explosions, the death of massive stars. In cool, dark clouds in the interstel- 
lar medium molecules, even somewhat complex ones, can form sometimes with the help 
of interstellar grains on whose surfaces they find fertile grounds for development. These 
grains are, of course, themselves assemblages of somewhat complex molecules. A great 
deal of terrestrial biochemistry takes place in liquid water. This cannot be the usual case in 
the interstellar medium. Table 1, taken from Ehrenfreund and Charnley (2000), lists organic 
molecules discovered thus far in the interstellar and circumstellar environments. Of partic- 
ular interest are the studies of infrared absorption spectra to young stellar objects embedded 
in cold dense envelopes. The line of sight typically passes through a large column density of 
interstellar ices. An example is seen in the spectrum of the star W33A, taken by the Infrared 
Space Observatory (Gibb et al. 2000) and shown in Fig. 4 where the absorption features of 
several organic molecules are identified. In recent years there has been an ongoing debate 
about the possible biotic origin of the 3.4 micron absorption signature of C-H stretching 
modes found in an amazing variety of objects, as shown in Fig. 5 taken from Ehrenfreund 
and Charnley (2000): the solid line is for an infrared galaxy at a distance of about 9x10® 
light years; the points are for the center of the Milky Way; the dashed line is for an organic 
residue of the Murchison meteorite. It appears that certain activities in carbon chemistry 
occur throughout the universe and there may be a rather universal reservoir of prebiotic 
organic carbon. However, from a study of the whole spectral region from 2 to 20 microns 
Pendleton and Allamandola (2002) conclude that there is no evidence for a biological origin 
to the 3.4 micron feature. 

6. Summary 

Since the physical evolution of the universe has led through increasing chemical complexity 
to the origins of biotic systems, an overview of recent results in cosmology is proposed as a 
background to discussions of the chemistry which led to life. Various independent methods 

TABLE 1. Interstellar and circumstellar molecules 









O u 
Z. U X' 

iri (N h1- 

u ^ u 


u u 

X X 
u u 


Ci (N 

m r~ T" 

S a: u 
y,u X u 




CJ \o 

iJm r- 

U U X 



^ X X £0 
U U Z y U X 

® X X U 8 X u 
U U U X X Z o 

+ o o 

^ zyxffixxx 


T' <N T' CO m m (N '7 



(N Z 

- ^ ^ 

U 5 Z o z 

z z s a: ° 



, o 

^ M- O, U r? 

^ ty-i ^ ^ ^ ^ o cj z y X" cj 



J. + + 

Kx NQZffiO^OoZc« + 




o&y raXXZOOo.Kuyxoc/3S^XzooS 

SiO CO 2 


Figure 4. Absorption spectrum in the line of sight to the protostar WW 33A. 

Wavelength (|im) 

Figure 5. The 3.4 micron absorption feature due to C-H stretching modes in various objects. See text for 
further discussion. 

conclude that the age of the universe is 13.7 ± 0.2 x 10® years. For the first time in the 
history of these determinations a decimal point has been placed on the year in which we 
celebrate the birthday of the universe. This is due in no small part to the refinements in 
old methods and to the development of new methods for determining large distances in the 


universe. It has become increasing clear that quantum cosmology has claimed priority in 
our attempt to understand the origin of the universe and that an inflationary epoch occurred 
very soon after that origin. The large scale distribution of luminous matter has become much 
better known with ambitious redshift surveys of galaxies and it appears that the distribution 
of all gravitating matter, including dark matter, follows this distribution. The largest scale 
on which the universe clumps is about 1500 times the size of the Milky Way. Structure as we 
know it today: stars, galaxies, clusters of galaxies, developed much earlier than expected, 
within perhaps 0.5 x 10® years of the universe’s origin and this claim is supported by recent 
measurements at high resolution of fluctuations in the cosmic background radiation. The 
rate of star formation is one of the principal elements in the development of structure and 
it now appears that many more massive stars were produced in the early universe than 
we had known previously. Organic chemicals are widespread in the universe, especially in 
star forming regions. There is increasingly persuasive evidence that numerous pathways of 
carbon chemistry are prevalent in the universe and that it contains a reservoir of prebiotic 
organic carbon. Other than what we find on the earth, there is to date no evidence that this 
has led to the formation of biotic systems. 

7. References 

Blaine, A.W. (2001) Starburst Galaxies, Berlin, Springer, p. 303. 

Cardone, V.F., Capozzielo, S., Re, V., and Piedipalumbo, E. (2002) A new method for the estimate of Hq from 
quadruply imaged gravitational lens systems, Astron. & Astrophys.382, pp. 792-803. 

Colless, M. (2003) The great cosmic map, Mercury 32, pp. 30-36. 

Ehrenfreund, R and Chamley, S.B. (2000) Organic molecules in the interstellar medium, comets and meteorites: 
A voyage from dark clouds to the early earth, Ann. Rev. of Astron. & Astrophys. 38, pp. 427^83. 

Frieman, J.A. and SubbRao, M. (2003) Charting the heavens, Mercury 32, pp. 13-21. 

Geller, M. (1990) Mapping the universe: Slices and bubbles. Mercury 19, pp. 66-76. 

Gibb, E.L., Whittet, D.C.B., Schutte, W.A., Boogert, A.C.A., Chiar, J.E., Ehrenfreund, R, Gerakines, P.A., Keane, 
J.V., Tielens, A.G.G.M., Van Dishoek, E.F., and Kerkhof, O. (2000) An inventory of interstellar ices toward 
the embedded protostar W33A, Astrophysical J. 536, pp. 347-356. 

Guth, A.H. andTye, S.-H.H. (1980) Phase transitions and magnetic monopole production in the very early universe, 
Phys. Rev. Letters 44, pp. 631-635. 

Hogan, C.J. (2002) The beginning of time, Science 295, pp. 2222-2225. 

Hoyle, F. and Vogeley, M.S. (2002) Voids in the point source catalogue survey and the updated Zwicky catalog, 
Astrophys. J. 566, pp. 641-651. 

Longair, M.S. (1996) Our Evolving Universe, Cambridge, Cambridge University Press, pp. 109-113. 

Lloyd-Ronning, N.M., Fryer, C.L. and Ramirez-Ruiz, E. (2002) Cosmological aspects of gamma-ray bursts: 
Luminosity evolution and an estimate of the star formation rate at high redshifts, Astrophys. J. 574, 554-565. 

Mangalam, A. (2001) Formation of a proto-quasar from accretion flows in a halo, Astron. & Astrophys. 379, 
pp. 1138-1152. 

Manning, C.V (2002) The search for intergalactic hydrogen clouds in voids, Astrophys. J. 574, pp. 599-622. 

Paczyhski, B. (1986) Gamma-ray bursters at cosmological distances, Astrophys. J. 308, pp. L43-L46. 

Paczyhski, B. (1998) Are gamma-ray bursts in star-forming regions?, Astrophys. J. 494, pp. L45-L48. 

Pendleton, Y.J. and Allamandola, L.J. (2002) The organic refractory material in the interstellar medium: Mid- 
infrared spectroscopic constraints, Astrophys. J. Suppl. 138, pp. 75-98. 

Roukema, B.F., Mamon, G.A. and Bajtlik, S. (2002) The cosmological constant and quintessence from a correlation 
function comoving fine feature in the 2dF quasar redshift survey, Astron. & Astrophys. 382, pp. 397^1 1. 

Saha, A., Sandage, A., Tammann, G.A., Dolphin, A.E., Christensen, J., Panagia, N. and Macchetto, F.D. (2001) 
Cepheid calibration of the peak brightness of type la supernovae, Astrophys. J. 562, pp. 314-336. 

Sandage, A. (2002) Bias properties of extragalactic distance indicators, Astron. J. 123, pp. 1179-1187. 



Centro de Astrobiologi'a ( CSIC-INTA ) 
Associated to the NASA Astrobiology Institute 
Carretera de Ajalvir, km 4 
28850 Torrejon de Ardoz, Madrid 

Living systems are examples of emergent behavior whereby complex chemicals assemble into 
hierarchical structures and systems with a collective set of properties that characterize them. 
We start by highlighting the basic properties of living systems in order that one can adopt an 
operational description (not really a definition) of living systems. This allows one to actually 
attempt a description of the properties of living systems and from there an unified description in 
terms of physics. Such a unified description can indeed be found by abandoning the traditional 
reductionist approach and using the notion of emergence. We give an analytical description of 
how emergence takes place. We will learn that the physics associated with the emergence of 
Life points towards the notion that life is a consequence of the evolution of the Universe. 

I. Introduction 

Today we recognize that the Origin of Life' on planet Earth must have involved at least the 
following phases: (1) synthesis of the basic chemical components and molecules; (2) transi- 
tion to a proto-biochemistry; that is, the formation of complex molecules capable of handling 
information, controlling self-reproduction, etc.; (3) RNA-to-DNA transition; (4) generation 
of a Proto-cell; (5) evolution into a cell. See for example Reference [1] for a description of 
the currently favorite “scheme”. 

This sequence points to an evolutionary pattern where certain out of equilibrium 
physico/chemical aggregates evolve from disordered configurations into ordered systems 
and where, in general, there are transitions from the “simpler” into the “more complex”. 
(Note that these stages can be viewed as a time-dependent “hierarchical” organization.) 

We will address the question of which fundamental physical principles must be at work. 
To use an analogy, what we will describe here puts together recent advances which can help 

* Inaugural Lecture delivered at the Symposium Celebrating the 50th Anniversary of Miller’s Experiment. 
Trieste, September 2003. 

^In honor of Professor Stanley Miller. 

* When we refer to life on planet Earth, the only one we know so far, we capitalize and write “Life”. Eor 
the generic phenomenon we will use lower caseand write “life”. 


J. Seckbach et al. (eds.), Life in the Universe, 27—51. 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


in establishing for the cell what the Carnot cycle is to the internal combustion, steam or 
engines in general. 

The material presented here has features of both, the bottom-up and top-down ap- 
proaches to the study of Life. From knowledge of the characteristics of living systems we 
can extract a generic set of properties that characterize living systems; from the current 
knowledge of the evolution of general out-of-equilibrium systems we can infer the prop- 
erties that the system must have in order to match the properties of living systems. These 
approaches meet at the Origin of Life and make its study an excellent scenario for the ap- 
plication and testing of ideas on the emergence and evolution of complexity. Furthermore, 
the ideas presented here have the advantage of being explicitly analytical and quantita- 
tive, and therefore are useful both in helping us understand the results of experiments and 
for proposing new experiments to understand the Origin of Life. Our aim is to provide a 
phenomenological framework for the study of these problems and contribute in helping to 
overcome the “intuitive understanding” that we now have. This time we find more than just 
“encouragement” as was the situation [2] ten years after Stanley Miller’s experiment, when 
J. Lederberg wrote that . .a consideration of contemporary theory on the origin of life is 
justified for two reasons: (1) exobiological research gives us a unique, fresh approach to 
this problem; and (2) we can find some encouragement that the recurrent evolution of life 
is more probable than was once believed.” 

For useful discussions on these topics, see for example References [3] and [4]. 

2. Some Generic (Basic) Properties of Living Systems 

To identify what physical phenomena underlie the origin of Life, we must first have a notion 
of “What is Life” [3]. This has been attempted many times (see for example [5] for a recent 
survey on this problem) and it may even be that it is not possible, so we must be for now 
contempt with just giving a “proxy description”: only in terms of its properties. 

We will describe the top-level properties of living systems. They will be used to give a 
list of the minimal set of properties that a system must have in order that it can qualify as a 
“living system”. In this way we will be able to infer the essential physics of such systems 
and, by exploring the physics, we will be able to say a lot about living systems and their 
potential origin. 

Somewhat vaguely, living systems are (1) open, (2) out-of-equilibrium^ (3) chemical 
systems with (4) limited available resources which (5) are subject to noise and fluctua- 

The properties of living systems can be roughly classified into three categories: (i) in- 
trinsic, (ii) operational (functional) and (c) historical (diachronic). The intrinsic properties 
are the ones with a phenomenology associated with the more essential or generic features 
of a living system; the operational properties are the ones that manifest by the expression 
or workings of the system. 

^ These systems can support long-range correlations generated out of shorter range interactions via the 
collective involvement of all the parts of the system. By short range we mean scales very small compared 
with typical system sizes. 


TABLE 1. Properties of Living Systems tabulated according as to whether they are Intrinsic, 
Operational or Historical in nature. We have (i) Replication/reproduction, i.e., the system is 
capable of giving rise to a new system, either by itself or by associating with other systems; 

(ii) Increasing free-energy gradient, the system is capable of changing its own free-energy by 
interacting with its environment; (iii) Robustness, meaning that the system maintains its integrity 
and operation under considerable changes in external conditions; (iv) Hierarchical/Modular 
(Scaffolding) organization, the system organizes itself into interconnected subsystems relevant for 
the stable operation of the full system. The next property we list is (v) Self-organization which 
means that the system organizes at all scales, both in space and in time, without any external 
intervention. Under (vi) Information we imply that the system is capable of both generating and 
handling external information in ways essential to being alive. They also display what is known as 
(vii) Collective/cooperative behavior. In these systems there is not only a free-energy flow but 
because of inhomogeneities and fluctuations in the system there are (viii) Fluctuations in 
free-energy which play a decisive role in the collective behavior. Next we list some basic 
Operational properties and finally the Historical properties of living systems. The (Darwinian) (i) 
evolution of living systems manifests through events that take place during a finite period of time 
and depends both on the set of circumstances intrinsic to the living system and those of the 
environment into which it is inserted. This is “historical” in nature: it manifests only after we 
compare records which are separate in time. There is an accumulation of change in the form of a 
more or less pronounced (ii) continuing novelty that eventually leads to (iii) transitions in the 
system. Sometimes these transitions involve such important quantitative and qualitative changes 
that they manifest in the form of major events in the historical process. Occasionally, these do not 
seem to be continuous, and instead manifest only after a period of subtle accumulated change; this 
is known as (iv) punctuated equilibrium, meaning that the changes that accumulate over time in 
the populations are so subtle that they seem to be in “equilibrium” until a certain threshold is 
reached and a new form of the system emerges. 

Properties of Living Systems 


Increasing free-energy gradient 

Hierarchy/Modular organization 

Information generation and Management 
Collective behavior 
Fluctuations in free-energy 


Interaction with the environment 
Metabolic networks 
Variation in reproduction 
Functional patterns 


Continuing novelty 
Transitions/Major Events 
Punctuated Equilibrium 

Finally, by historical properties we mean the global manifestations of the living system 
as time elapses. Living systems change with time both at the level of the individual sys- 
tem and at the population or species levels. These properties are summarized in Tables 1 
and 2. 


TABLE 2. The above characteristics of Living Systems lead to establishing 
an analogy with stochastic non-linear out of equilibrium systems with many 
chemical species in interaction. 

Features of Life as an Assembled Chemically Operated System 

a Self-Reproduction 

b Dynamical stability when subject to fluctuations: chemical/Quantum-Thermal 
c Hierarchical Organization 
d Chemical Patterns in space-time 
e Metabolism 

f Information storage and processing 
g Adaptation/Functional interactions with environment 
h Living/lineage evolve 


With this we can begin to draft a definition of a living system. It can be done in at least two 
ways: via a “synthetic” definition and via an “operational” definition. We will not pursue 
synthetic definitions here^ . 

An operational definition allows one to capture the properties of living systems by 
making direct reference to their general properties. The most complete"^ is that Life is a self- 
reproducing, dynamically stable to environmental fluctuations, hierarchically organized set 
of chemical space-time patterns, which collectively are capable of metabolizing, storing 
and processing information, adapting to the environment and whose assembled results are 
evolving lineages. 

3. The Physics of Generic Systems with the Basic Properties of Living Systems 

The above signatures and properties are known from work carried out over the last two 
decades, that they are present in condensed many-body systems with dynamics involving 
both random and regular attributes. 

These systems can be modeled in terms of sets of Stochastic, PArabolic, NOn-linear, 
Differential Equations (SPANODES) [7]. As a particular application of these equations we 
have the spatio-temporal evolution of a chemical species in interaction with itself, other 
species and a fluctuating environment. We will see that this provides a rich scenario for the 
study of the Origin of Life. 

The parabolic character of the equation ensures that the system is out of equilibrium 
(as in diffusion) and that there are next-to-nearest-neighbor interactions in the species’ 

^ An example of a “synthetic” definition is furnished by the following: “life is a self-sustained chemical 
system capable of undergoing Darwinian evolution". 

Except for the inclusion of fluctuations and the specificity to chemical processes, this definition of Life 
is due to Farmer and Belin [6]. The fluctuations could be quantum, thermal or chemical fluctuations due to 
the presence of composition inhomogeneities in the system or in the environment. 


concentration. This is so because parabolic partial differential equations involve the first 
derivative with respect to time of the unknown and therefore imply that there is the time 
asymmetry present in out-of-equilibrium systems. Parabolic partial differential equations 
involve the laplacian of the unknown quantity (say the concentration of a chemical species); 
the laplacian being a second derivative involves comparisons of the unknown at three 
consecutive space points. In this part of the collective dynamics there are contributions 
from both, the regular and the random characters. The regular come from the nature of 
the derivatives (differences between values of the unknown function at different points in 
space and time). The random character is present because the parabolic character implies 
the existence of irreversibility and this irreversibility ultimately can be traced to the presence 
of thermal and quantum fluctuations [8]. 

When there are many species involved in the dynamics many possibilities open up. From 
the existence of chaotic behavior as in the Rossler oscillator to the existence of synchronous 
patterns, the appearance of small worlds or the emergence of the various collective behaviors 
[9] . This is mostly regular in its character. 

Non-linearity ensures the presence of reaction terms: the species in the system will mix 
with each other and/or themselves. If the mixing term is non-linear then it can generate 
new species out of the original species and, simultaneously, do it in a way that goes beyond 
simple additivity. Again this is mostly regular in nature. 

The stochastic feature models the presence of noise or any other fluctuation in the 
system. Noise is nothing but a means of (a) summarizing the contribution to the dynamics 
of degrees of freedom whose typical scales are smaller than the scales at which we study the 
system or (b) modeling the contribution to the dynamics of non-deterministic^ processes 
which can only be statistically characterized through some probability distribution. 

These systems model at a very basic level a time-dependent flow of free-energy which, 
due to the presence of reaction-diffusion and a random component, becomes scale dependent 
both in space and in time. 

Next we briefly discuss some of their phenomenological features. 


These systems display critical behavior. That is, for certain values of the parameters in the 
system such as reaction or diffusion constants, the short range forces acting among the 
components of the system “align”, and the correlation between components does not decay 
exponentially. The system enters into a regime with pure power law correlations. This 
has very deep and important consequences. Exponential decay is associated with some 
dominant length scale and the system is not scale invariant. When the system enters into a 
power-law correlation regime it becomes scale invariant and very long range correlations 
between parts of the system are established: there is collective behavior! The transition into 
these regimes is of course what happens when a system experiences a phase transition (see 
Figure 1). 

^ Note the implication that this has for “reductionist” views. The presence of non-deterministic processes, 
even if they can be statistically represented by a noise term, implies that one is giving up the standard 
reductionist views. 


a P 

0 < 















Figure 1. Change in the ground state (phase) of a system as the relevant control parameter evolves with scale. 
The ground state is the most stable state and corresponds to the lowest potential energy. In C, we indicate a 
situation where a “tunneling” phenomenon could happen: the system tunnels from state a to |3. 

The systems we are considering are out of equilibrium; the phase transitions are said 
to be dynamical [10]. These phase transitions in chemical systems are known to lead not 
only to long range correlations, but also to self-organization and hierarchical organization 
[9] and [11], Which type of organization the system follows depends, as we will see later, 
on the nature of the scaling exponent in the power law: for imaginary exponents the system 
organizes into hierarchies. We will also see that the values of the exponents, and hence 
the nature of the critical point, are related to how the physical parameters change with 
length/time scales, a process known as “coarse graining” of the system. As in the better 
known equilibrium phase transitions the system goes into very different states depending on 
the side of the critical point where it sits. For example, below the critical point the system may 
be in its solid state whereas above the critical point it could be in a liquid or gaseous state. 

In addition, the states into which these systems transit can be very robust, implying that 
the system will have a tendency to organize itself into such states and to remain in them. 
This is often seen in living systems, where a particular pattern such as DNA chemistry, 
embryonic development or eyes, once they emerged, are used over and over again in the 
evolution of Life. They are states that organize themselves into spatial “clusters” [ 1 2] or into 


temporally synchronized phenomena, very much like the songs of crickets or the croaking 
of frogs in the night of a tropical forest. Additionally, these systems display geometrical 
patterns or even complex patterns that move together through space as time elapses. Some of 
them can even “spontaneously” “arise” and “die”! or evolve through variation [12] induced 
by fluctuations. Their potential for complexity generation is huge. 

What we have just described are precisely the properties of what are now called “Emer- 
gent Phenomena”. These phenomena and an analytical framework to describe them will be 
presented in some detail in the next section. For now, we simply remember that emergent 
behavior is usually associated with the simultaneous presence of (a) Collective Phenomena, 
(b) Evolution, (c) Self-organization, (d) Generation of Patterns, (e) Scaling behavior (not 
geometrical or engineering scaling!), (f) Hierarchical organization and (g) the Assembly of 
the “Probable into the Little-Probable”®. Hence Emergence provides a unifying theme from 
Cosmological and Astrophysical phenomena into Biological and Ecological phenomena 
where all of the above are known to take place. 

4. What Is Emergence? How Can It Be Described? 

Emergence can be defined as what occurs in phenomena where “the whole is more than 
the simple sum of its parts”. This happens, for example, in an ant hole where we see that 
the capabilities of the ant colony go far beyond the ability of a single ant. This is because the 
whole includes not only the individual ants, but also their social relations, communication 
abilities, etc. [14]. 

In prebiotic chemistry we can think of a “chemical soup” with many chemical species 
present in an environment where the chemicals are “stirred” by some noise. The chemicals 
interact among themselves as well as with the environment. The chemical system is open, 
i. e., exchanges energy and matter with the environment. The combined effect of non- 
linear interaction, spread in space, temporal and spatial evolution, as well as stochastic 
effects, are various forms of self-organized behavior; the “soup” goes into different basins 
of attraction for the parameters, each of these basins characterize the “emergent” behavior 
of the system. Emergence is what takes place when the system goes from one state into 

In chemistry we can think of the aromatic properties of benzene as an emergent property 
of aromatic rings. Or we can think of emergence in more complex systems like reaction 
networks, metabolism or living cells. Another example is provided by the processes from 
musical tones to notes to the emotion generated by listening to the music. 

Emergence is (1) associated with the spatio-temporal evolution of the system and (2) 
related to scale (and complexity) changes in the system. 

Properties (1) and (2) above imply that emergence arises when coarse-graining an open 
system. Coarse-graining [15] a system is the process of studying the system at different 
spatial and/or temporal scales. Or the process of considering various parts of the system 

® Holland (page 231 of Ref. [13]) puts this as “Transformation from the extremely unlikely to the likely”, 
meaning that once a little -probable configurations have emerged, they become very common and are used 
as “parts” of larger, more complex, systems. For example, once eyes emerged. Life has used them over and 



by averaging out subsets of the system’s degrees of freedom. In other words, as we coarse 
grain a system and take into consideration more and more of the details of its components, 
we also perceive an increase of the number and classes of states to which the system has 
access. The result is emergent behavior. 

5. “Predicting” Emergent Behavior. The Dynamical Renormalization 
Group and Emergent Behavior 

Let us consider a generic many body system. Let us for the sake of the argument assume 
that its components are very diluted and that, in addition, they interact very weakly with 
each other. Under these conditions the whole is simply the sum of its parts and one does 
not expect any cooperative phenomena to arise: additivity is all we will see. 

Next, imagine that we substantially increase the number of components to the point 
where the interactions between them become more significant. This has the implication that 
new states become available to the system as the relevance of the interactions is enhanced. 
Due to the non-linear character of the interactions the principle of superposition does no 
longer apply, but conservation of energy or maximization of available entropy may force 
the interacting parts of the system into assuming new configurations. Let us also have the 
system exchange energy and/or matter with its environment, i.e., let the system be open. 
Then the system may fragment or coagulate into new systems which, effectively, maintain 
some of the properties that made the original system stable. Not just any energy/matter 
transfer rate will lead to stable configurations. There will have to be, at least, some balance 
between the strength of the interactions and their associated rates, the energy/matter transfer 
and the relaxation times of the new states assumed by the evolving system. Many of these 
phenomena could be due to processes taking place at scales smaller than the one at which 
we are observing the system: to what we have called “noise”. 


The scale at which we study the system is thus basic to understand the phenomena that we 
observe in a many-body system. To implement “coarse graining” requires that we introduce 
a description of the physical variables (such as concentrations) in terms of fields, space-time 
dependent quantities which evolve according to some equations. We study these systems 
using what is known as Statistical Field Theory (see [10] and references therein), one 
example of which is provided by the previously mentioned “spanodes”. 

Observing the system at different scales and connecting the results of these observations 
to a phenomenological description means that we average the quantities in the system over 
some (graining) scale. In particular this implies that parameters such as viscosities, reaction 
“constants”, masses, noise amplitudes, etc., become scale dependent. The scale dependent 
parameters are called “effective parameters” and they obey some ordinary differential equa- 
tions which describe how they change with scale. For example, in chemical reactions the 
reaction rates become scale-dependent and make the dynamics scale-dependent. 

In general these differential equations have “fixed points”. That is values of the param- 
eters which remain independent of scale changes. When the parameters have these values, 
the system becomes scale independent and, therefore, all scales in the system participate in 


its dynamics. The system is scale independent and the correlations must become power law 
correlations (cf. Appendix A). These are “critical states” and the transition from one state 
to another as the graining scale changes is called a “phase transition” (see Figure 1). The 
power laws are characterized by some (calculable) exponent which depends on the values 
at the fixed point of the effective parameters. For out of equilibrium systems, these states 
have all the properties described earlier for “emergent” states and we can calculate many 
of their properties even if we cannot predict in complete detail all of them. The system is 
not fully reducible. 

There exists a quantitative and qualitative tool that allows us to carry out such calcu- 
lations. It is known as the Renormalization Group (RG) and has been extensively used in 
many body phenomena^ as well as in particle physics. It is now finding application in many 
other realms of science, including Biology and Ecology. We explore how this happens. 

5.1.1. Combining regular and random dynamics. The tools, (i) The effective action 
and (ii) the RGBs 

In statistical mechanics, the full description of a system is given in terms of a partition 
function. In a statistical field theory there is an analogue of the partition function that can 
be calculated and from which all the physical parameters can be derived; the Generating 
Functional, Z[J; {a,}]. Here J{x, t) represents the source for the field 4>(.v, t) and the ct, 
represent the couplings in the system, i. e., reaction constants, masses, etc. 

The generating functional comes with a problem which turns out to be a boon: it is 
plagued by divergences. But removing them is precisely what allows one to coarse grain the 
system! The divergences imply the existence of a scale that is either very large or very small 
compared with the length/time scales typical of the system. In some cases the divergences 
can be systematically removed by introducing an arbitrary length scale \. The scale X. is 
called^ the “sliding scale” and can be identified with the “graining” scale. The mathematical 
procedure for removing the divergences is called “renormalization”. Systems for which this 
is possible are called “renormalizable”. 

This procedure introduces a \-dependence in Z[/] which now becomes Z[/; {a,}; X]. 
Since the scale X was arbitrary, we must have that 


X ^ ^ 0. (1) 

The only way this can be satisfied is if the couplings themselves become scale dependent 
and satisfy equations equivalent to Eq. (1). These equations are the Renormalization Group 
Equations RGEs mentioned above. They are of the form, 

^^ = -(3c,({a,}), (2) 

^ The RG was introduced in the early fifties by Peterman and Stuckelberg and, independently by Gell-Mann 
and Low [16]. In the 60’s and 70’s it was extended to many-body systems. In fact, the 1982 Nobel Prize in 
Physics was awarded to K. Wilson for his application of the RG to the study of equilibrium phase transitions, 
and in 1991 to P. G. de Gennes for his application to the study of polymer dynamics. 

* Because the calculations are usually performed in momentum space, instead of configuration space, the 
sliding scale is usually taken in the literature to be its inverse, a momentum scale p,. Here we will always 
refer to the length scale X as the sliding scale. 


where the (non-linear) function (3a, ({aj}) can be explicitly calculated and contains the 
combined effect of the regular and fluctuating parts of the dynamics. 

5.1.2. Power laws, (i) Real and (ii) complex exponents. Some examples 
Since the generating functional satisfies Equation (1) and the derivatives of the generating 
functional with respect to the source J give the correlation functions for the field® 4>, 
Gjv(ri, . . . , r]v; {oty(X.)}; X.), it follows that the correlation functions also satisfy RGBs. These 
are partial differential equations whose coefficients are functions of the various coupling 
parameters and which, as was the case for the Pa, ({«; }), can in general be calculated using 
perturbation theory. The 7 <|,({ay}) are the anomalous dimensions of the field 4>, and they are 
to 4> what the Pa, were to the a, . They are of the form, 



G^(ri,...,r^;{a,.(\)};\) = 0 

( 3 ) 

and can be immediately solved using the method of characteristics. Their solution is 

Gw(n,r2, ...,rA,;{aj(\)};\) 

= GjvCri, T 2 , . . . , rjv; {a;(Xo)};Xo) x exp 


( 4 ) 

Here the subindex zero refers to a reference value: the length scale corresponding to the 
system configuration that we have observed and where the parameter had measured values 

Near a fixed point of the couplings, i. e., for those values a,- = a* where Pa, ({a*}) = 0, 
the couplings go to their constant fixed point value and the integral in the above N-point 
correlation function becomes proportional to log In other words. 

Here is the value of the anomalous dimension when the couplings are at their fixed 
point values. Note from the last line that at the critical point the correlation functions follow 
a power law and, as advertised earlier, the system is scale invariant and therefore all its 
components are involved in the dynamics: there emerges a cooperative phenomenon that 
involves the full system and which self-organizes all of its parts. 

In the case of the two-point correlation function (2PCF) Equation (5) becomes 

G'^’’irx, ti;r 2 , t 2 ) oc \r^ - r 2 ?-^F(^ (6) 

Vki - ri\^/ 

^ In the following, and for the sake of brevity, the r* represent with a single symbol the space-time coordinates 
Xk and t* . 


with X and z related to various suitably chosen (for convenience) combinations of anoma- 
lous, engineering and space dimensions. The scaling function F{u) can be shown to have 
the limiting behaviors 

lim F{u) oc constant (7) 

w — >0 

for small argument values, and 

lim F{u) oc (8) 

W— >-oo 

for large argument values. 

There are many examples in the literature of the above. A particularly useful one is 
provided by the evolution of an incompressible fluid subject to a stirring force which is 
random in both space and time [17]. This system is very generic in its properties and may 
be used to model many different physical situations from the evolution of the Universe at 
large scales, to self-reacting chemical systems to hypercycles. It has fixed points for the 
noise couplings which are both real and complex. The real fixed points lead to the standard 
power laws familiar from chemical kinetics [11]. The complex fixed points lead instead to 
hierarchical behavior [18]. One can also treat the case of several coupled chemical species 
[12], but the currently available calculational techniques escalate very quickly in complexity 
with the number of species and the only way to proceed is by numerical calculation where, 
unfortunately, there can be a loss of intuition. 


The deep reason why there are complex fixed points of the RG is as follows; because the 
system is not isolated and exchanges energy and matter with its environment, it does not 
have symmetry under time reversal and conservation of probability no longer holds. This 
opens up the possibility for fragmentation and coagulation phenomena together with self- 
organized behavior in these systems. Coarse graining out of equilibrium systems is the tool 
to describe the large class of phenomenological behaviors observed in these systems. Each 
set of fixed points defining an “emergent state”. The global properties of these states are 
determined by the stability properties of the fixed points. 

To understand this, we need to imagine the system at some fixed scale. At this scale 
reaction constants, diffusion constants, etc., will have some fixed values. As we change 
scale these couplings evolve according to their RGEs and “move” into different values. 
Towards which states the system evolves depends on where in the “basins of attraction” 
of the various fixed points are the initial values of the couplings. The system will “transit” 
to the new state corresponding to the couplings towards which it is being attracted (see 
Figure 1). 

We can now describe in some useful detail how the phenomenon of “emergence” takes 
place in these systems. 

In the system of ordinary differential equations Eq. (2) we can have various stability 
situations depending on the nature of the eigenvalues of the matrices characterizing the 
linearized version of the system. We can have improper nodes, saddle points, proper nodes, 
degenerate improper modes spiral points and centers. They can be attractive or repulsive at 


either short or long length scales. Each of these stability classes gives rise to a particular 
phenomenology and associated pattern. In going from one size scale to another the state of 
the system changes and its global stability properties also do change. 

Once a fixed point is reached, the properties and patterns corresponding to this particular 
state become manifest. If the new state is stable, the emergent state will be “persistent”. 
On the other hand, if the state is only metastable, the system will display emergence into 
a new ephemeral state'®. However all parts of the system are fully involved in its dynam- 
ics and this dynamics, in turn, drives the system into the emergence of a self-organized 

The M -point correlation functions are the coefficients in the functional expansion of 
the probability distribution function (PDF) [19]. In fact, the PDF can be shown to satisfy 
an RGE [20] which is a generalization of Eq. (3). The various emergent behaviors are 
characterized by the properties of the PDF in the basins of attraction of the respective fixed 
points. Of course these properties mirror and refine the results that are derived from the 
simpler 2-point correlation functions. 

Thus the emergence of complexity is to be studied by analyzing the scale-evolution 
of the PDF. The consequences of this are very deep: emergent behavior cannot be fully 
predicted although it can be characterized in terms of some basic effective parameters. The 
most one can make are probabilistic statements about the accessible states. These states can 
be identified for each level of description or of the hierarchy in the system. Full reducibility 
is not possible and we enter into a new realm where the binomial complexity/simplicity is 
harmonized through probability. 



It can be seen (cf. Appendix A) that because of the implied scale invariance, the real 
exponents are indicators of cooperative behavior. These exponents can be measured by 
studying log-log graphs of the correlation functions which in the scaling (power-law) regime 
will show up in this graph as a straight line with slope given by the exponent. The more 
negative an exponent is the tighter the correlation between components located at the various 
points to which the n -correlation function refers. 

Let us restrict ourselves to the two-point correlation function (2PCF), which together 
with the one-point correlation function determines the PDF for gaussian processes. The 
2PCF is the joint probability of finding two objects located in two independent volume 
elements. Since the 2PCF is a probability, it must be a real quantity. This has very important 
implications in the physical interpretation of complex exponents. 

We now examine the behavior of the 2PCF in the limit of large spatial separation. As we 
saw in Eqs. (6) and (7) the two point correlation function for the fluctuation in concentration 
of a chemical species, 8p(r), measured at points r and r' has in the critical regime the form 

(8p(r')8p(r)) oc |r — (9) 


The state could also be an ephemeral but synchronous state. 


where the angle-brackets denote that an ensemble average has been taken. Let us assume 
that X is complex and given by x = X« + iX/ • Then, since the 2PCF is real, Eq. (9) becomes 

(8p(/-') 8p(r)) = Rece'^ 



c • r 

- r'|2x« 


p -h 2x/ log 

( 10 ) 

Here the quantities c, tq, and p are constants. They are obtained by direct comparison with 
the experimental results. The form of Eq. (10) in a log-log plot is that of a log-periodic 
function modulated by a power law. The periodicity shows up in the form of “wiggles” in 
the graph of the 2PCF. The period of the logarithmic periodicity is controlled by x/ while 
the slope of the modulating power law is controlled by x« • 

From Eq. (10) one obtains that maximal correlation occurs for finite-size regions which 
are quantized by an integer n and whose size is given by 

k(«) - r'\ = ro ■ exp 



[tan \xr/Xi) 

P] -(e^T = A-b" 

( 11 ) 

with n = 0, ±1, ±2, . . .. We conclude that 

(i) there is a hierarchy of regions of average linear sizes R(„) = |r(„) — r'\ such that 
correlation on those scales is favored. 

(ii) the hierarchy can be classified according to an integer n, and 

(iii) note also that within each level of the hierarchy the correlation is a power law. 

In other words, for systems away from equilibrium, the collective organization of the 
system leads to self-organized cooperative behavior and, in some instances, the system self- 
organizes into interrelated regions whose average finite sizes can be classified according 
to integers. These regions are nested within each other and have the property that at a 
given level they all seem similar, however their specific small scale properties can be quite 
different. This is what is understood by a hierarchy (see for example [21] and [22]). 

Examples of the phenomenology just mentioned are abundant. They range all the way 
from the large scale structure of the Universe, to planetary systems, to geological faults, 
to chemical networks and cellular automata, evolutionary games and replicators, fragmen- 
tation and coagulation phenomena, proteins, allometries in living systems and ecologies. 
They also include self-replicating networks, catalytic hypercycles and the emergence of 
environmentally selected evolutionary pathways. All these are examples of “systems”, as 
discussed by Miller [23] more than two decades ago, but in a new incarnation and with a 
vengeance: we can describe them numerically (through algorithmic simulations) and are 
well on our way to describe them analytically, from first principles. 

6. The Emergence of Life and the Evolution of the Universe 

The history of the Universe started about 13.7 Gyr ago, when the period known as the Big- 
bang took place. It is a story progressing in space and time where at each stage the dominant 


Figure 2. An iconic representation of the evolution of the Universe and Life. 

forces have generated characteristic structures and patterns. The evolutionary histories of 
the Universe and of Life are iconically depicted in Figure 2. 

These patterns have to do with properties such as “synchronization”, “networks”, “emer- 
gence”, “scaling” and “hierarchies”. All of them are part of what is now known as “com- 
plexity science” or “complexity theory”. Complexity theory tries to identify non-obvious 
patterns of self-organization in Nature that occur in complex systems, i.e., in systems where 
“the whole is more that the sum of the parts”. Thus, trying to understand if “Life is a cos- 
mic imperative” [24] or, more precisely, if “Life is a consequence of the evolution of the 
Universe” [25], i.e., that it emerges every place in the Universe where there is an oppor- 
tunity for chemical evolution, requires that we frame these questions within the context of 
“complexity theory”. Complexity theory becomes the basic analytical tool for describing, 
understanding and unifying astrobiological phenomena. 

The presence of scale invariance with real and/or complex exponents is one of the 
hallmarks of self-organized behavior. As is the generation of complexity in open out of 
equilibrium systems. The existence of power laws in the galaxy-to-galaxy correlation func- 
tion has been known for a long time as well as a similar relation for clusters of galaxies 
and other structures. This can be understood as a consequence of the evolution of matter in 
gravitational interaction in the noisy environment provided by the Universe itself [26]. The 
fragmentation of the initial structures into their various hierarchical fragments (top-down 
components such as clusters of galaxies, galaxies of the various types, clusters of stars and 


the various types of molecular clouds) can also be described in terms of this evolution in 
an amazingly precise way [27]. At these scales the dominant few body force is the gravita- 
tional force. At smaller scales the dominant interaction is the electromagnetic force which 
dominates through chemistry and its many allied macroscopic processes. 


In correspondence with the above one can estimate the free-energy-rate density" involved 
in these processes to find [30] that, considered as a function of the structure size-scale, it 
follows a power law! Therefore, these structures and their emergence fit very well into the 
notion we have developed here of a hierarchical and self-organized emergent system. One 
can extend this calculation to living systems and find thaf indeed they also follow the same 
pattern of power laws with a common exponent; all the way from large clusters of galaxies 
to ecosystems there is a power law dependence of the free-energy-rate density. This is an 
excellent token connecting the evolution of structure in the Universe with the evolution 
of living systems. It should be telling us something about the period when the transition 
between them took place: the Origin of Life (at least!) on Earth. It is furthermore telling 
us that the Origin of Life can be considered as yet another (emergent) manifestation of the 
evolution of the Universe. 


Since the Universe is out of equilibrium, one expects to have complex exponents in the 
correlation functions. It therefore comes as no surprise that the Universe, at large scales, 
self-organizes into hierarchies. At smaller scales it is also expected that hierarchical orga- 
nization will emerge, because the non-equilibrium of the Universe is true at all scales. This 
hierarchical organization can be appreciated in the following example, which is a direct 
application of the out-of-equilibrium hierarchy theory deduced from Eq. (11). 

If we study the two-point correlation function for matter density fluctuations from the 
average density, 8p(ic, t), corresponding to the large scale structures in the Universe, all the 
way from the known horizon to the various classes of molecular clouds, one predicts [18] 
that each structure type j has a typical mass contained within a region of size R^jy, and 

that they are related by ~ ^2.|75± 0.075 observational data for all the structures 

is best fit by ~ which agrees, within the estimated uncertainties, with 

what is predicted. Predictions and observations are plotted in Eigure 3. 

The data for all the structures can be fit by the power law of Eq. (10). Erom this 
one predicts the existence of a mass-size hierarchy, and the size for each structure-type is 
predicted to be given by R(„) = |r(„) — r'\ asinEq. (ll),with A = (3.92 ± 0.67) x 10^® cm 
and b — 9.02 ± 0.24. This is represented in Eigure 4. Similarly, the mass is predicted to be 
— (123 ± 27)" X [(2.46 ± 0.62) x 10^°] g. In Eigure 5, we plot these predictions 

* * The free-energy density can be obtained from the partition function by using the standard procedures of 
statistical mechanics. It follows once the n-point correlation functions are known. See for example [28] and 
for a more advanced treatment [29]. What follows can therefore be interpreted as a manifestation of the 
power-law behavior for correlation functions that has been described above. 


Mass vs. Longitudinal Size 

10 ” 


10 = 

10 = 

10 " 

10 " 



10 = 

10 = 


Molecular Clouds through Galaxies and Superclusters 

10^= io'^ 10’= 10=’ 10== 10== 10== 10== 

Longitudinal Size (cm) 

Figure 3. Mass vs. longitudinal size distribution of discrete structures in Universe from molecular clouds 
through galaxies to superclusters of galaxies and power law fit (slope = 2.10 ± 0.07). 

Size Scale vs. Hierarchy Index 

Molecular Clouds through Galaxies to SuperClusters 

10 == 

10 == 


10 == 

„ 10 == 

1 . 10 =" 


^ 10 == 


W 10=’ 

10 =“ 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 

Hierarchy Index 

• Observed Structures 

□ Predicted Typical Size 
O Unobserved Structures 

Figure 4. Longitudinal size scale vs. hierarchy index n for discrete structures in Universe from molecular clouds 
through galaxies to superclusters of galaxies and predictions from Eq. (11). The value of b is 9.02 ± 0.24. 


Mass vs. Hierarchy Index 

Molecular Clouds through Galaxies to SuperClusters 

Figure 5. Mass vs. hierarchy index n for discrete structures in Universe from molecular clouds through galaxies 
to superclusters of galaxies and theoretical predictions from hierarchy theory. The value of b is 9.02 ± 0.24. 

for the masses together with the observed values. The observed data is best fit by = 
(98.8 ± 11.1)" X [(7.64 ± 4.82) x 10^°] g. The agreement between this quantity and the 
prediction is also well within the observational uncertainties. 

These hierarchies can be iconically represented like a pyramid on whose vertex is 
the most encompassing class of structures. Together with power-law correlations at the 
individual levels, they imply the presence of a network (in this case a “scale-free” and 
“hierarchical” network [31]). For gravity-dominated structures we display this in Figure 6 
which is to be understood only as a metaphor for Figures 3 to 5. See also [32]. 

A similar situation is known for living systems (see for example Refs. [33], [34] and 
references cited). There is ample evidence of power-law behavior for metabolic rate vs. 
mass all the way from bacteria to elephants and whales, and an analogous relationship is 
known to hold for plants over several orders of magnitude. In addition, there is evidence 
that the traditional organizational levels in the cell, the genome, transcriptome, proteome 
and metabolome are associated with networks governed by principles similar to the ones 
just described except that they are chemically operated (see Figure 7). As will be argued 
below, their generated complexity is therefore much greater. 

Note also that each level in the hierarchy has a characteristic mass/size relationship. 
And that this is true for both gravity and chemistry dominated structures. For example, 
galaxies have a typical sizes and the same, in general, is true for cells. 


Figure 6. An iconic representation of the Hierarchical Levels of Organization in the Universe. 

For gravity induced structures, one can construct arguments which fall under the (rather 
unfortunate!) name of the Anthropic Principle and which shed lots of light on their nature 
and how they are formed [35], The features shared with living systems seem to suggest the 
existence of an analogous principle for living objects; the chemically dominated structures. 
But these relations still await discovery and much experimental as well as phenomenological 
work needs still be done in this area. 


We have argued that Life is not only chemically based, but that it also fulfills all the ba- 
sic properties of emergent, complexity generating and out-of-equilibrium phenomena. The 
complexity of a system is related (in ways we still do not completely understand) to the 
number of states accessible to the system. Of the two long-range fundamental interac- 
tions, the gravitational and the electromagnetic forces, the strongest and the one with more 
potential for generating complexity is the electromagnetic interaction when acting at the 
atomic/molecular and mesoscopic levels. That is, when the conditions are such that chemical 


Information sioraga 


Figure 7. The main hierarchical levels in present day living systems. Taken from reference [34], 

processes can happen. We then expect to have emergence of life in those out-of-equilibrium 
environments where the conditions for the emergence of some complex chemistry with 
some sufficient degree of stability (but still out-of-equilibrium) are met, as was discussed in 
the introduction to Section 5. The transition from simpler to more complex chemistry must 
have taken place as the environmental and kinetic conditions for Life became compatible. 
Once the conditions for a sufficiently complex chemistry were present, then the laws of 
physics as discussed here inevitably lead to systems with the properties of Table (2): the 
combined action of the electromagnetic force and quantum mechanics (chemistry) leads to 
the assemblage of supramolecular structures with the basic properties of the living systems 
that we see today. Properties such as hierarchical organization, metabolic networks, etc. 
are the indicators of what must have been at work during the Origin of Life. This provides 
us with useful guidance to reconstruct or try to reproduce the steps listed in Section 1. 
Something that may have happened at many locations in the Universe where the conditions 
for this class of universal phenomena were possible. 

The fact that we know of common regimes as described above for both living and non- 
living organized matter, already gives us clues to use in understanding the transition. We 
observe that there is a larger change in the free-energy-rate density for living things than for 
non-living matter. It is conceivable that such changes are favored because of the existence 
of a hierarchical organization. This is, for example, the case in metabolic activity where 


due to the help of enzymes, many complex chemical reactions take place individually and 
reversibly; however, when put together they constitute an irreversible process. 

With the hierarchical self-organizing principles that we have discussed here we begin to 
envisage scenarios for the sequential origin of Life mentioned in Section 1 and in Ref. [1]. 
Indeed, the presence of hierarchical (or modular) organization is an excellent vehicle for the 
use of the available free energy, while allowing synchronicity to occur. At a global level, this 
is facilitated by the formation of membranes, itself a dynamical critical phenomena [25], 
[36]. Note also that staging is of importance in synchronization as well as in increasing 
free-energy gradients; processes that would otherwise be very fast can be slowed down and 
thus lead to more stable collective configuration which, in addition, are more robust and 
complex due to the increase in the interaction probability. 

7. Reprise: Using Contemporary Physics in the Study of the Origin of Life 

We are now in a position to suggest new scenarios for prebiotic chemistry experiments. We 
need to design experiments where there is self-replication leading to some form of hierar- 
chical organization of the reaction byproducts which can be maintained by an in-flow of 
energy. The chemistry does not have to happen all at the same time. Instead and as described 
in Section 1, it is conceivable that there is a sequence of events that manifest as some form 
of a time-sequence. These events could be linked by a tendency to favor maximization 
of order by using available free-energy. This can happen by assembly of smaller/simpler 
components into a more “efficient” system to deal with the environment surrounding it 
and giving rise through this process a form of emergent behavior. The emergent chemical 
dynamics can have a temporal hierarchical behavior, i.e., be sequential. There can even be 
the combined effect of space and time hierarchical behaviors ! 

Thus we need to design experiments with reaction kinetics that leads to complex expo- 
nents (not only real exponents) in the correlation functions. This can be accomplished by 
making appropriate choices of environmental parameters such as pressures, temperatures, 
fluctuations of various types (“noise”) or the chemical substrate on which the chemical 
reactions takes place, just to mention a few possibilities. Under these conditions and based 
on the guidance that physics gives us, one can expect the spontaneous emergence^^ of states 
where the available free-energy-rate density jumps by amounts large enough to saturate the 
available complexity gaps. 

It has already been mentioned that stirring or random-forcing of many-component chem- 
ical reactions can lead to collective self-organized behavior, including hierarchies. This 
seems to be a very basic feature of complex systems with a high potential to reproduce 
the phenomenology of living systems [12]. This spontaneous emergence of “living-like” 
order reminds one of what happens in some cases of structure formation in the Universe. 
For example, in the formation of stars there are regions of space-time which for some ran- 
dom reason have a higher concentration of matter/energy; this concentration, with the help 
of self-gravitation, can reach the levels required by the nuclear force to initiate a fusion 

Technically, what can happen is that, due to the imaginary component of the exponent, there is “tunneling” 
between states. 


reaction and start the burning into a star. This process is described (except for the origin of 
the primeval fluctuation) by the Oppenheimer-Volkoff theory of star formation, and is very 
much at the basis of what we know today about star formation. It is conceivable that an anal- 
ogous process of “concentration” (enrichment) of complexity potential and free-energy-rate 
density gradients could do it for Life. Of course one cannot simply go and take any arbitrary 
chemicals: many must probably be involved, but a judicious choice of compounds is needed. 
The choice could be informed by involving chemicals that lead to both a large number of 
reaction by-products which are sufficiently stable so as to increase the probability of further 
reaction or chemical-node formation in the emergent chemical networks. 

There are several strategies that may be used to implement the ideas discussed here. They 
must involve theoretical and phenomenological exploration of the principles just discussed 
combined with the power of (numerical) molecular dynamics simulations. From these one 
can design actual chemical experiments and even attempt biological synthesis experiments. 
Crucial to these experiments is the assembly or integration of the various components at 
each hierarchy level, both in length (spatial hierarchy) and in duration (temporal hierarchy). 
The integration could be self-organized if the conditions are such that the free-energy-rate 
density has the levels required by emergent hierarchical behavior as described here: then 
the system maximizes correlation for a given available energy. Given a self-replicating 
heteropolymer, not every sequence-length will work: only those that follow hierarchical 
behavior and overall power-law in the dependence of the free-energy-rate density with size 
(and/or time) should work. 

These considerations can be of use in some of the “Life in a Test Tube” experiments being 
performed now [37] where a phage is constructed from synthetic oligonucleotides. One of 
the main difficulties encountered in these experiments lies in the “error-free” assembly 
of long-enough genome segments of the known sequence using synthetic oligonucleotides. 
The removal of this and allied problems can benefit from the hindsight gathered by analyzing 
the assembly with the techniques discussed here and in [12] and [20]. 

8. Conclusions 

We have described the basic properties of living systems and shown how they are unified by 
current notions of emergent phenomena. These can be analytically studied through a class 
of stochastic systems which (1) can model systems of many-chemical species in reaction- 
diffusion configurations inserted in a noisy environment; (2) lead to the notion that Life is a 
consequence of the evolution of the Universe and (3) can be effectively used to guide in the 
design of experiments and the proposal of scenarios to understand, albeit in a non-reducible 
and to a certain extent probabilistic way, the Origin of Life. 

The Origin of Life is an extraordinary held to experimentally test ideas on emergence. 
Emergence becomes an overarching theme that connects the evolution of Life with the 
evolution of the Universe, and allows the application of the scientific method to these 
problems. Phenomenological studies indicate that Life can be integrated with the evolution 
of the Universe which, for chemically dominated matter, naturally leads via a “bottom-up” 
scenario to the notion that the Universe must be teaming with life. 

Many outstanding problems can benefit from the application of the guidance provided 
by the methods and results discussed here. They range from understanding in detail the 


chemical reaction dynamics of complex chemical systems with hierarchical correlations, 
to the bottom-up approach to the synthesis of Life, to the top-down synthesis of living 
organisms in the test tube. It is of special interest to combine the methods described here 
with the top-down synthesis of living systems, where they can for example, help in providing 
effective methods for the synthesis of the target genome. 

But even the successful generation of quasi-living or living systems does not solve the 
problem of the Origin of Life, since we would then need to correlate the synthetic genome 
with the current notion about LUCA (Last Universal Common Ancestor). The physics we 
have at our disposal today can greatly help in these issues, and we are rightfully hopeful, 
but lots of creative work from people from many disciplines still needs to be done, even if 
we now have much more guidance than 50 years ago. 


The author thanks Herrick Baltscheffsky, Baruch Blumberg, Esteban Domingo, 
Murray Gell-Mann, Alvaro Gimenez, Terry Goldman, David Hochberg, Andy Knoll, 
Bemd-Olaf Kiippers, Jonathan Lunine, Martin Rees, Bruce Runnegar, Jack Szostak, 
Gunther von Kiedrowsky and Geoffrey West for many discussions on the many issues 
discussed in this paper. Finally, I wish to thank Julian Chela-Flores for his vision and 
Joseph Seckbach for his encouragement, patience and professionality. 


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(1986) 1235. 

Appendix A: Scale Invariance and Power Laws 

Let us quickly show how the connection between scale invariance (hence collective behavior 
and a basic ingredient of self-organization) arises mathematically. For this we consider a 
function f{x) of a variable x and subject the independent variable x to a change of scale as 

X Xx (Al) 

Here X. is the scale factor, which for infinitesimal changes is convenient to take as 
X R:! 1 -f €, with 6 much smaller than 1. Scale invariance of the function f(x) means that 


under the scale change in Eq. (Al) the function behaves as 

f(x) = -fO^x) 



where the affine parameter a must be not equal to one. Expanding in a Taylor series we 
find that for X. close to 1 , the above equation turns into an easily solved ordinary differential 

df a — I dx 

= (A3) 

/ 6 X 

whose general solution is 

^ a — I 

fix) — Constant • x — (A4) 

i.e. a power law with exponent x ■ We see at once that scaling invariance of a function 
Eq. (A2) implies that its functional form must be the one of a power law. And because scale 
invariance means that all the scales in the system are involved in its dynamics, we have the 
statement that scale invariance is the harbinger of collective behavior. But the solution of an 
ordinary differential equation requires that we impose some boundary or initial condition. 
The condition here is that Eq. (A4) must reproduce Eq. (A2), and this leads to [38] the 
conclusion that in general x is of the form 

In a 2tt 

X = = x« + *X/ (A5) 

with n = 0, 1, 2, . . . i.e., the scaling exponent x can be both real or complex. Eurthermore, 
the imaginary part is discrete and quantized by the natural'^ numbers. 

Appendix B: Synopsis 

We have seen that for many body systems where one can write evolution equations of the 

Flow with Time = Spatial Diffusion + Reaction + Noise (Bl) 

for the various species making up the system, there is a redistribution of the available free- 
energy; and with this a flow of free-energy. Given some initial and boundary conditions for 
the fields and parameters, the system goes into configurations where a stable state is reached 
at a rate faster than the “thermal” approach and there are catalysis and“Darwinian evolution”. 
In addition persistent patterns as well as hierarchical organization and synchronization 
emerge by coupling enhancement [12]. 

The above suggest a “picture” of life fitting in the evolution of the Universe as one 
more phenomenon that takes place as soon as the conditions for the emergence of complex 

There are not many generalizations of the proportionality factors. By studying the statistical mechanics of 
power laws in a general framework one finds a straightforward connection with the Riemann Zeta function, 
I, . In this case the complex exponents are related to the zeroes of i : each zero leads to a full family of 
complex exponents ! [7] 


chemistry are present. The phenomenon of Life on Earth would be just one example of a 
Universal phenomenon, very much as our galaxy or our Solar System are only one instance 
among many in the Universe. 

There is, however, a very basic difference: due to the interplay between the presence of 
noise, the large number of complex available states, the possibility of reaction between many 
different components and the scale dependence of the final states, one cannot give a fully 
deterministic description and has, instead, to resort to a description in terms of probabilities. 
The result is a non-reductionist approach to the Origin of Life and its Evolution. 

II. Where did the Chemical Elements Come 
From and When did Life Begin? 



^ Department of Astronomy, University of Trieste, Via G.B. Tiepolo 11, 
34131 Trieste, Italy and ^Astronomical Observatory of Trieste (INAF), 
Via G.B. Tiepolo 11, 34131 Trieste, Italy 

1. Introduction 

We discuss the origin of the cosmic abundances of the chemical elements and in particular 
of biogenic elements such as H, C, N, O and Fe. Interesting enough, many of these elements 
are among the most abundant in the Universe. 

The solar system abundances of chemical elements measured in the Sun photosphere 
and in meteorites represent the chemical composition of the gas at time of formation of the 
Solar System (4.5Gyr ago). The solar chemical abundances are called Cosmic Abundances. 
The cosmic chemical composition can be described by three quantities: X = 0.71, Y = 
0.27, Z = 0.02, representing the abundance by mass of H, He and metals (all the elements 
heavier than He). In fact, when considering elements other than H and He, we find that C, 
O and N are among the most abundant metals. 

By means of a chemical evolution model for the Galaxy together with our knowledge 
on stellar evolution it is possible not only to reproduce the observed solar abundances but 
also predict the evolution of chemical elements in time. Chemical evolution models also 
predict abundance variations inside the galaxy as by instance, abundance gradients along 
the thin-disk. This can be interesting in view of some recent results (Santos et al. 2000) 
suggesting that a higher than solar Fe abundance favors the formation of stars hosting 
planets. In fact, due to abundance gradients, we would expect a larger fraction of stars 
hosting planets towards the inner disk where the Fe abundance is larger. 

2. The Production of the Light Elements 

While all the metals have originated in stars, the light elements (H, D, He and ^Li were cre- 
ated during the Big Bang and some of them (He, Li) also in stars. The main phases of the Big 
Bang nucleosynthesis can be summarized as follows: at T = lO'^K only weak interactions 
causing conversions between protons and neutrons occurred, whereas the nucleosynthesis 
started when T = lO^K and lasted until T = 10*K. At that point the deuterium followed 
by Helium and lithium were formed. Then also very small fractions of ^Li (10“^ by mass) 
were produced. 

One of the major achievements in cosmology is that the Big Bang Nucleosynthesis 
(BBN) can account simultaneously for the primordial abundances of H, D, ^He, "^He and 


J. Seckbach et al. (eds.), Life in the Universe, 55 — 58 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


^Li. The BBN and CBR (Cosmic Microwave Background, WMAP experiment) measures 
agree on the same value for the baryon/photon ratio t] = 6.1 x 10“'° which implies a 
baryonic density for the universe Qh ~ 0.0224 (Bennet et al. 2003; Spergel et al. 2003). 
The primordial chemical composition was then X = 0.76, Y = 0.24, Z = 0. 

3. The Production of “Metals” 

All the elements contained in the 2% of the cosmic chemical composition have then been 
manufactured in stars. Elements with mass number A from 12 to 60 have been formed 
in stars during the quiescent burnings during stellar evolution. Stars transform H into He 
and then He into heavier until the Fe-peak elements, where the binding energy per nucleon 
reaches a maximum (A ~ 56). 

Hydrogen is transformed into He through the proton-proton chain or the CNO-cycle, 
then ^He is transformed into through the triple-a reaction: 

"'He + "'He -> *'Be 

*Be -b ^He ^ + 7+7 

The triple-ot reaction is a resonant reaction and creates C in an excited state. This is 
probably the reason why carbon has survived instead of reacting with a-particles and give 
rise to '°0. The above reaction (triple-a) is very important for the terrestrial life which is a 
carbon-based chemistry. 

Oxygen and a-elements (O, Ne, Mg, Si, S, Ca) originate from the capture of a-particles 
and the chain arrives until the formation of ^^Si. The last main burning in stars is the 
^*Si-burning which produces ^°Ni which then decays into ^°Co and ^°Fe. Si-buming can be 
quiescent or explosive (depending on the temperature) and it always produces Fe. Explosive 
nucleosynthesis occurs during Super Nova (SN) explosions and mainly produces Fe-peak 
elements. Finally, s- and r-process elements (elements with A > 60 up to Th and U) are 
formed by means of slow or rapid (relative to the p-decay) neutron capture by Fe seed 
nuclei and are produced during He-burning and SN explosions, respectively. 

4. The Dispersal of Elements from Stars 

Supemovae and stellar winds restore the newly synthesized and the old elements into the 
interstellar medium (ISM). Type II supemovae or core-collapse supernovae originate from 
the explosion of stars with M > 8 Msun- They contribute mainly to Oxygen and other a- 
elements (Ne, Mg, Si, S, Ca) plus some Fe and Fe-peak elements. Type la SNe are believed 
to originate from white dwarfs in binary systems exploding by C-deflagration. They produce 
mainly Fe. Carbon and Nitrogen are mainly produced in intermediate and low mass stars 
(0.8 < M/Msun < 8). In particular, carbon is produced via the triple-a reaction which acts 
in stars of masses larger than 0.5Msun, whereas nitrogen is a product of the H-burning 
via the CN and CNO cycle and generally is a secondary element (produced from C and 
O already present in the stars). Possible mechanisms such as dredge-up and rotation can 
however produce primary nitrogen. 


Time (Gyr) 

Figure 1. The predicted temporal evolution of the abundances of C, N, O in the gas in the solar neighbourhood, 
from the model of Chiappini et al. (2002). The various curves refer to different nucleosynthesis prescriptions. 
The large symbols indicate the solar abundance measurements according different authors (for more details 
see Chiappini et al. 2002 and references therein). 

5. Stars as Probes of Chemical Evolution 

Four main stellar populations inhabit the Galaxy; halo, thick-disk, thin-disk and bulge. 
Galactic chemical evolution models take into account the star formation history in galaxies 
plus the nucleosynthesis and predict the evolution of the abundances of the most common 
chemical elements in the gas in galaxies. In particular, a model of the chemical evolution 
of the galactic disk should reproduce the solar and present time abundances observed. 

The abundances of C, N, O as all the abundances of the elements heavier than "^He 
increase with the cosmic time whereas H is consumed but only in a negligible amount. In 
Figure I we show an example of predicted temporal evolution of the abundances of the C, 
N, O elements in the solar neighbourhood by the model of Chiappini et al. (2002). 

6. Conclusions 

By comparing the predictions from chemical evolution models and observational data we 
can conclude that: 

• Carbon is mainly produced in stars with masses in the range 2-8 Msun> and partly 
by massive stars. The bulk of this element is produced on timescales >250Myr. 

• Nitrogen is also mainly produced in stars with masses in the range 2-8 Msun on 
relatively long timescales but its production is complicated by the secondary /primary 
processes in stars. The bulk of this element is also produced on timescales ~250Myr. 

• Oxygen is mainly produced by massive stars on very short timescales (from few 
Myr to 30Myr). 


• Iron is mainly produced on long timescales (> 1 Gyr) by type la SNe, which originate 
from white dwarfs in binary systems with initial masses in the range 0.8-8 Msun 
on long timescales (> IGyr). 

• If a higher than solar Fe content favors the formation of planetary systems (e.g. 
Santos, Israelian & Mayor, 2000), then we should expect to find them preferentially 
towards the galactic center, because of the existence of a gradient in [Fe/H] as 
measured from stars (Matteucci, 2001). 

7. References 

Bennet, C. L. Halpem, M., Hinshaw, G., Jarosik, N., Kogut, A., Limon, M., Meyer, S. S., Page, L., Spergel, D. N., 
Tucker, G. S., Wollack, E., Wright, E. L., Barnes, C., Greason, M. R., Hill, R. S., Komatsu, E., Nolta, M. R., 
Odegard, N., Peiris, H. V., Verde, L. and Weiland, J. L. (2003) First- Year Wilkinson Microwave Anisotropy 
Probe (WMAP) Observations: Preliminary Maps and Basic Results. ApJS 148, 1-27. 

Chiappini, C., Romano, D. and Matteucci, F. (2003) Oxygen, Carbon and Nitrogen Evolution in Galaxies. MNRAS 
339, 63-81. 

Matteucci, F. (2001) The Chemical Evolution of the Galaxy, ASSL, Vol. 253, Kluwer Academic Publishers, 
Dordrecht, The Netherlands. 

Santos, N. C., Israelian, G. and Mayor, M. (2000) Chemical Analysis of 8 Recently Discovered Extra-solar Planet 
Host Stars. Astron. Astrophys. 363, 228—238. 

Spergel, D. N., Verde, L., Peiris, H. V, Komatsu, E., Nolta, M. R., Bennett, C. L., Halpern, M., Hinshaw, G., 
Jarosik, N., Kogut, A., Limon, M., Meyer, S. S., Page, L., Tucker, G. S., Weiland, J. L., Wollack, E. and Wright, 
E. L. (2003) First- Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of 
Cosmological Parameters. ApJS 148, 175-194. 



University of Geneva - Observatory of Geneva 
Chemin des Maillettes 51, 1290 Sauverny-Switzerland 

1 . Introduction 

In the conventional view the Universe began in a hot Big Bang some 15 billions years 
ago, and has been expanding ever since. The dark age of the Universe is pointed out as the 
period between the hydrogen recombination epoch and the horizon of current astrophysical 
observations. At very early stage in the expansion, when the temperature of the Universe was 
still 10^-10^° K, collisions between subatomic particles created hydrogen and helium nuclei 
with very minor traces of deuterium and lithium nuclei. The chemistry of the early Universe 
is the chemistry of these light elements. This chemistry (Standard Big Bang Chemistry or 
SBBC) has been source of large studies. One of the most important consequences, of the 
existence of a significant abundance of molecules, is the crucial role played in the dynamical 
evolution of the first collapsing structures. The arrow of time in the cosmic history describes 
the progression from simplicity to complexity, because the present Universe is clumpy and 
complicated unlike the homogeneous early Universe. Thus it is crucial to know the nature 
of the constituents, in order to understand the conditions of the formation of the first bound 
objects. In this paper we analyse the chemical history of this Dark Age and the consequences 
on the birth of the first astrophysical objects. Thus in section 2 we describe the chemical 
evolution of the Universe, then in section 3 we analyze the implications on the formation 
of first stars. In section 4 some possible outlooks are pointed out. 

2. Primordial Chemistry 

During the recombination period the ions became progressively neutralized, which led to 
molecular formation. Nevertheless at early epochs where a total absence of dust grains 
appears justified, fhe chemisfry is different from the typical interstellar medium astrochem- 
istry. Some groups proposed an assembled comprehensive set of reactions for the early 
Universe, such as Lepp and Shull (1984), Puy et al. (1993), Galli and Palla (1998), Lepp 
et al. (2002) and Puy and Pfenniger (2003). The chemical network is coupled with the 
temperatures (radiation and matter) and the matter density. The evolution of baryons de- 
pends on the expansion and on the chemical kinetic, when the radiation only depends on 
the expansion. Matter temperature depends on different factors such as expansion, coupling 
between free electrons and background photons, and thermochemistry (see Puy et al. 1993, 


J. Seckbach et al. (eds.), Life in the Universe, 59 - 62 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. Evolution of abundance in the SBBC. Vertical axis characterizes the abundances when the horizontal 
axis is relative to the redshift. (a) describes the He-chemistry, (b) the H-chemistry, (c) the D-chemistry and 
(d) the Li-chemistry, see Buy and Pfenniger 2003. 

Puy and Pfenniger 2003). We started our calculation at the redshift z, = 10“* where the Uni- 
verse is full ionized, and stop the integration at = 10 where the process of reionization is 
supposed to act up (see Bennett et al. 2003). We pull the initial abundances of the standard 
big bang nucleosynthesis (see Cyburt et al. 2003, Puy and Pfenniger 2003). 

Helium is the first neutral atom which appeared in the Universe, then charge transfer 
initiate neutral formation (see Fig la). Despite the absence of any surfaces of dust grains, it 
is possible to form neutral molecules through the radiative association between two neutral 
atoms. Nevertheless H 2 cannot form by this radiative process, charge transfer from H 2 "'" 


become an alternative or associative detachment with see Fig 1(b). HD has perma- 
nent dipole moments which lead to the capacity to be formed by radiative association. 
Nevertheless HD formation is more significative, when H 2 appeared, through the dissocia- 
tive collision with D+, see Fig 1(c). Besides the radiative association, LiH can be formed 
from Li by exchange reaction with H 2 , by associative detachment with H~ or by mutual 
neutralization process (LH’H“^or (Li“’H). see Fig 1(d). 

3. Formation of the First Structures 

In the post recombination context, H 2 HD and LiH have a negligible role on the thermal 
balance of early Universe (see Puy et al. 1993, Pfenniger and Puy 2003), but these primordial 
molecules play a role in the dynamics of the first objects in the primordial gas (Puy and 
Signore 1996). HD and H 2 are important coolant agents and initiate, in numerous cases, the 
process of thermal instability then the mechanism of fragmentation. The study of forming 
structure is crucial, in the bottom-up hierarchical picture of structure formation; earliest 
baryonic objects provide the elementary building blocks for larger mass objects that form 
later. First massive objects could be early stars, which contaminate the medium with metals, 
through supernova-driven winds, then lead to a chemistry of heavy elements (see Harwitt 
and Spaans 2003). The recent discovery of a high optical depth Thomson scattering from 
the WMAP date implies that significant reionization took place, see Bennett et al. (2003). 
Reionization theory can be supported by a scenario of early star formation, see Loeb and 
Barkana 2001. 

4. Outlooks 

Many important questions still await answers. SBBC is still in a nascent stage and the 
development of computing techniques and software for the quantum mechanics will open 
large possibilities. Pfenniger and Puy (2003) suggested that primordial molecules H 2 and 
HD can freeze out and lead to the growth of flakes of solid H 2 and HD at z ~ 6-12 in 
the unperturbated medium and under-dense regions. Thus in the current understanding of 
the formation of the first bound structures during the dark age, the possibility that solid 
hydrogen flakes exist and modify the subsequent evolution must be considered. More re- 
cently Puy and Pfenniger (2003) showed that SBBC is sensitive to density perturbations, 
and lead to relative abundance variations of several percents. Larger variations are expected 
in the non-linear phases such as collapses. A definitive understanding of the collapse of 
the first structures is still lacking, because the coupling of gravity, chemistry, and radiation 
constitutes a formidable non-linear system for which not all equations are presently well 
known. This question is central because provide strong indications on the mass of the first 
formed stars, and ultimately knowledge on the contamination in heavier elements at high 
redshifts. Chakrabarti and Chakrabarti (2000) suggested that adenine formation is possible 
by successive addition of HCNs in collapsing clouds. Thus as soon as protostellar processes 
occur, carbon chemistry can be developed then lead to different ways of early pre-biotic 
molecular formation. In conclusion, molecules have influenced the births and distributions 
of all stars and galaxies, often by serving as coolants but in other ways as well. Moreover 


astrochemistry produces species that sometimes have never been manufactured in detectable 
quantities in terrestrial laboratories. Chemistry of the first objects is not complete, as the 
chemistry of life in the Universe is a central and unsolved question. For the post-life chem- 
istry as Coyne (2001) pointed out: In some extraordinary chemical process the human brain 
came to be, the most complicated machine that we know. . . 

5. Acknowledgements 

I would like to thank Professor Chela-Flores and Professor Joseph Seckbach for the orga- 
nization of this conference and of these proceedings, and Flavia Puy for discussions on the 
origin of life. This work was supported by the Swiss National Science Foundation and the 
University of Geneva. 

6. References 

Barkana, R., and Loeb A. (2001) In the beginning: The first sources of light and the reionization of the Universe, 
Phys. Report 349, 125-238. 

Bennett, C., Halpern, M., Hinshaw, G., Jarosik, N., Kogut, A., Limon, M., Meyer, S., Page, Spergel, D., Tucker, 
G., Wollack E., Wright, E., Barnes, C., Greason, M., Hill; R., Komatsu, E., Nolta, M., Odegard, N., Peirs, H. 
and Verde L. (2003) Eirst year Wilkinson microwave anisotropy probe (WMAP) observations: Preliminary 
Maps and Basic Results AstrophysicalJ. Supp. 148, 1-27. 

Chakrabarti, S., and Chakrabarti, S. (2000) Can DNA bases be produced during molecular cloud collapse? 
Astrophy and Astrophys. Letters 354, L6-L8. 

Coyne, G. (2001) Origins and creation, in First steps in the origin of life in the Universe Eds J. Chela-Flores, T. 

Owen and F. Raulin, Kluwer Academic Publishers, pp. 359-364. 

Cyburt, R., Fields, B., and Olive K. (2003) Primordial nucleosynthesis in light of WMAP, Phys. Letters B 567, 

Galli, D., and Palla, F. (1998) The chemistry of the early Universe, Astrophysics and Astrophysics 335, 403—420. 
Harwitt, M., and Spaans, M. (2003) Chemical composition of the early Universe, Astrophy. J. 589, 53-57. 

Lepp, S. and Shull, M. (1984) Molecules in the early Universe, Astroph. J. 280, 465^69. 

Lepp, S., Stancil, P, and Dalgarno, A. (2002) Atomic and molecular processes in the early Universe, J. of Phys. 
B: Atomic, Mo. and Optical Phys. 35, R57-R80.. 

Pfenniger, D., and Puy D. (2003) Possible flakes of molecular hydrogen in the early Universe, Astrono. and 
Astrophys. 398, 447^54. 

Puy, D., Le bourlot, J., Leorat, J., Pineau des Forets, G., and Alecian, G. (1993) Formation of primordial molecules 
and thermal balance in the early Universe, Astrono. and Astrophys. 267, 337—346. 

Puy, D., and Signore, M. (1996) Primordial molecules in an early cloud formation, Astrono. and Astrophys. 305, 

Puy, D., and Pfenniger, D. (2003) Differential chemistry in the early Universe submitted to Astronomy and 



^Department of Earth Sciences, Oxford University, Parks Road, Oxford 
0X1 3PR, UK and ^ACQUIRE, The University of Queensland, St Lucia 
Qld 4072, Brisbane, Australia 

I. Introduction 

Valid claims for reliable recognition of Earth’s earliest biological remnants or by-products 
must be based on the following minimum requirements: i) geologically correctly identified 
rocks; ii) correctly and precisely dated rocks; iii) accurately localised rocks of which a type 
specimen is kept in a collection accessible to international researchers; iv) chemical, isotopic 
or morphological data which can discriminate between a biological and non-biological 
origin; v) samples which have been totally decontaminated from extraneous, unrelated 

These requirements are just as essential for ancient terrestrial rocks as for meteoritic and 
planetary materials. Because of inadequate investigation of materials of potential biological 
interest by one or more of the above criteria, it is evident that most (if not all) recent claims 
for presence of biosignatures in Earth’s most ancient rocks are either wrong or, at best, 
highly debatable. Here we summarise a few examples from recent literature. 

2. Claims for Biogenicity Based on Morphology 

Putative bacterial or cyanobacterial microfossils from the 3 .47 Gyr Apex chert from Western 
Australia were long thought to provide the oldest morphological evidence for life on Earth 
(Schopf, 1993). These microstructures have recently been re-interpreted (B raster et al. 2002) 
as secondary, non-biological artefacts formed from amorphous graphite within multiple 
generations of metalliferous hydrothermal vein chert and volcanic glass, thus offering no 
support for primary biological morphology. Regardless of the significance of reduced carbon 
in these rocks, this particular example illustrates the importance of correctly identifying the 
host sample, which Schopf (1999) described as graded sediments that were deposited near a 
river mouth. However, field mapping has shown them to be hydrothermal veins that crosscut 
a stack of volcanic pillow basalts (Brasier et al. 2002). 

Repeated claims (Pflug and Jaeschke-Boyer, 1979; Pflug, 2001) for spherical micro- 
fossils, named Isuasphaera isua (Pflug) in chert from the 3. 7-3. 8 Gyr Isua greenstone belt 
(IGB) from southern West Greenland, have recently been re-investigated (Appel etal. 2003). 
The site was revisited in 2001 and it was shown that extreme stretching deformation of the 
metamorphosed chert could not possibly have preserved spherical objects from the time 


J. Seckbach et al. (eds.), Life in the Universe, 63 - 66 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


of chert deposition, and are therefore not primary features. These spherical objects were 
clearly formed by post-tectonic processes, probably related to pre-Quaternary weathering. 
This is in broad agreement with high-resolution SEM data (Westall and Folk, 2003) on 
samples of nearby Isua cherts and banded iron formation (BIF). The latter contain abundant 
remains of fossilised cyanobacteria, fungi and spores, as well as varied carbonaceous par- 
ticles, between grains and on fracture surfaces. These are regarded as less than 8000 years 
old, because the area was until recently covered by ice. 

3. Claims for Biogenicity Based on Carbon Isotopes 

Strong claims for biogenicity of '^C-depleted graphite microparticles in the mineral apatite 
from >3.8 Gyr-old metamorphosed chemical sediments on the island of Akilia of southern 
West Greenland have long been defended (Mojzsis etal. 1996; Nutman et al. 1997). The sit- 
uation regarding the age of the carbon-bearing rocks, as well as the nature of their geological 
relationship to the dated rocks, was summarised in the previous Trieste Conference Volume 
(Moorbath, 2001), and is not repeated here. Since then, it has been demonstrated (Fedo 
and Whitehouse, 2002) that the crucial carbon-bearing rocks on Akilia Island, misidenti- 
fied (Mojzsis et al. 1996; Nutman et al. 1997) as chemical sediments, are actually banded 
quartz-pyroxene rocks of mixed magmatic and metasomatic (fluid-penetrated) parentage 
with no intrinsic biological relevance whatever. 

The overall debate about interpretation of C isotope ratios has taken a major step forward 
both from study of ancient reduced carbon and modern seafloor hydrothermal systems. 
In genuine chemical sediments (including BIF) of the 3. 7-3. 8 Gyr IGB, some 150 km 
northeast of Akilia Island, ^^C-depleted graphite particles have been claimed as evidence 
for biological activity (Schidlowski, 1988; Mojzsis et al. 1996). However, it has been 
shown (Lepland et al. 2002; van Zuilen et al. 2003) that graphite in IGB rocks occurs 
abundantly only in secondary carbonate veins formed at depth in the crust by injection of 
hot fluids reacting with older crustal rocks (metasomatism). During these reactions, graphite 
is formed by disproportionation of FeCOs at high temperatures (^450° C) by the reaction 
OFeCOs ^ 2 Fe 304 + SCOi + C. Van Zuilen and co-workers call for a reassessment of 
earlier interpretations of life at 3.8 Gyr made on these carbonate-rich rocks, and conclude 
that the isotopic composition of graphite, in general, does not serve as a reliable biomarker 
in strongly metamorphosed rocks. 

Discovery of highly reduced gases (H 2 and methane) in vent fluids of the presently active 
Mid- Atlantic Rainbow hydrothermal system (Charlou et al. 1 998) has opened the possibility 
of studying an active site of abiogenic hydrocarbon production. Holm and Charlou (2001) 
reported abiogenic (de novo) synthesis (of the Fischer-Tropsch type) of linear saturated 
hydrocarbons with chainlengths between 16 and 29 C atoms. Horita and Berndt (1999) 
measured C-isotope compositions of dissolved methane from Rainbow vent fluids and 
found a similar extent of isotopic fractionation as in microbial methane. Hence, isotopically 
light C in graphite on its own as preserved in ancient rocks is not sufficient evidence to 
imply biogenicity. 

There is one occurrence of abundant reduced carbon in a 3. 7-3. 8 Gyr IGB metamor- 
phosed sediment (not hydrothermally altered mafic rock) which was claimed to contain bio- 
genic ^^C-depleted graphite, putatively derived from the detritus of planktonic organisms 


(Rosing, 1999). This is so far the most plausible prospect for early life in IGB rocks, but 
these rocks are highly deformed and strongly metamorphosed (at garnet-grade). Further- 
more, because these rocks have anomalous tungsten isotope ratios the possibility needs to be 
considered that the reduced carbon could be meteoritic in origin (Schoenberg et al. 2002). 

In short, several much publicised claims for biosignatures in early Archaean rocks of 
West Greenland are highly questionable, whilst some are certainly wrong. In particular, we 
emphasise that morphological studies as well as stable isotope analyses of minute amounts 
of retrieved ‘organic’ material need to exclude the effects of contamination by modern 

4. Discussion 

There is still no undisputed evidence for when and where life started on Earth. Methods for 
investigating the oldest rocks for biosignatures require far greater geological and geochemi- 
cal sophistication than evident in most published efforts. A major limitation is the uncertainty 
surrounding the true nature of host rocks that are claimed to contain biosignatures. However, 
progress is being made in establishing morphological, mineralogical, chemical and isotopic 
fingerprints of microbial carbonates (rocks that form due to the decay of microbial organic 
matter). Presently, the oldest known such deposits have been documented from the 3.4 Gyr 
Warrawoona Formation in Western Australia (Van Kranendonk et al. 2003). Microbial car- 
bonates allow for detailed direct chemical comparisons between ancient sedimentary rocks 
with biopotential and modern examples. 

The cumulative effects of the putative, massive Late Heavy Bombardment of the Earth 
at around 3. 9^.0 Gyr on life (if present) were arguably devastating. But we know for sure 
from evidence of surviving rocks (e.g. the IGB sedimentary and volcanic rocks) that by 3.7- 
3.8 Gyr geological processes at and near the surface of the Earth were becoming recognisably 
uniformitarian, perhaps allowing life to get started in leisurely fashion under relatively 
quiescent conditions on mineral surfaces in metaphorical Darwinian “warm little ponds”. 

5. References 

Appel, P.W.U., Moorbath, S. and Myers, J.S. (2003) Isuasphaera isua (Pfiug) revisited, Precambr. Res. 126 
pp. 309-312. 

Brasier, M.D., Green, O.R., Jephcoat, A.P., Kleppe, A.K., van Kranendonk, M.J., Lindsay, J.F., Steele, A. and 
Grassineau, N.V. (2002) Questioning the evidence for Earth’s oldest fossils. Nature 416 , pp. 76-81. 

Charlou, J.L., Fouquet, Y, Bougalt, H., Donval, J.P., Etableau, J., Jean-Baptiste, P, Dapoigny, A., Appriou, P. and 
Rona, P.S. (1998) Intense CH 4 plumes generated by serpentinisation of ultramafic rocks at the intersection of 
the 15°20’N fracture zone and the Mid-Atlantic Ridge, Geochim. et Cosmochim. Acta 62, pp. 2323-2333. 

Fedo, C.M. and Whitehouse, M.J. (2002) Metasomatic origin of quartz-pyroxene rock, Akilia, Greenland, and 
implications for Earth’s earliest life, Science 296 , pp. 1448-1452. 

Holm, N. and Charlou, J.O. (2001) Initial indications of abiotic formation of hydrocarbons in the Rainbow 
ultramafic hydrothermal system, Mid-Atlantic Ridge, Earth Planet. Sci. Lett. 191 , pp. 1-8. 

Horita, J. and Berndt, M.E. (1999) Abiogenic methane formation and isotopic fractionation under hydrothermal 
conditions. Science 285, pp. 1055-1057. 

Lepland, A., Arrhenius, G. and Cornell, D. (2002) Apatite in early Archaean Isua supracrustal rocks, southern 
West Greenland: its origin, association with graphite and potential as a biomarker, Precambr. Res. 118 , 
pp. 221-241. 


Mojzsis, S J., Arrhenius, G., McKeegan, K.D., Harrison, T.M., Nutman, A.P. and Friend, C.R.L. (1996) Evidence 
for life on Earth before 3,800 million years ago, Nature 384 , pp. 55-59. 

Moorbath, S. (2001) Geological and geochronological constraints for the age of the oldest putative biomarkers in 
the early Archaean rocks of West Greenland, In: J. Chela-Flores, T. Owen and F. Raulin (eds.) First Steps in 
the Origin of Life in the University, Dordrecht: Kluwer Academic Publishers, pp. 217-222. 

Nutman, A.P, Mojzsis, S.J. and Friend, C.R.L. (1997) Recognition of >3850 Ma water-lain sediments in West 
Greenland and their significance for the early Archaean Earth, Geochim. et Cosmochim. Acta 61 , pp. 2475- 

Pflug, H.D. (2001) Earliest organic evolution. Essay to the memory of Bartholomew Nagy, Precambr. Res. 106 , 
pp. 79-91. 

Pflug, H.D. and Jaeschke-Boyer, H. (1979) Combined structural and chemical analysis of 3,800 Myr-old micro- 
fossils, Nature 280 , pp. 483^86. 

Rosing, M.T. (1999) ^^C-depleted carbon microparticles in >3,700-Ma sea-floor sedimentary rocks from West 
Greenland, Science 283, pp. 674-676. 

Schidlowski, M. (1988) A 3,800-million-year isotopic record of life from carbon in sedimentary rocks, Nature 
333 , pp. 313-318. 

Schoenberg, R., Kamber, B.S., Collerson, K.D. and Moorbath, S. (2002) Tungsten isotope evidence from ~3.8 
Gyr metamorphosed sediments for early meteorite bombardment of the Earth, Nature 418 , pp. 403—405. 

Schopf, J.W (1993) Microfossils of the early Archaean Apex Chert: New evidence of the antiquity of life, Science 
260 , pp. 640-646. 

Schopf, J.W. (1999) The Cradle of Life, Princeton University Press, New York. 

Van Kranendonk, M.J., Webb, G.E. and Kamber, B.S. (2003) New geological and trace element evidence from 
3.45 Ga stromatolitic carbonates in the Pilbara craton: support of a marine, biogenic origin and for a reducing 
Archaean ocean. Geobiology 1, pp. 91-108. 

Van Zuilen, M.A., Lepland, A., Terranes, J., Finarelli, J., Wahlen, M. and Arrhenius, G. (2003) Graphite and 
carbonates in the 3.8 Ga-old Isua supracrustal belt, southern West Greenland, Precambr. Res. 126, pp. 331- 

Westall, F. and Folk, R.L. (2003) Exogenous carbonaceous microstructures in early Archaean cherts and BIFs 
from the Isua greenstone belt: implications for the search for life in ancient rocks, Precambr. Res. 126 , 
pp. 313-330. 



Centre de Biophysique Moleculaire, CNRS, 

Rue Charles Sadron, 45071 Orleans cedex 2, France 

I. Introduction 

The question of the chemical origins of life is engraved in the European scientific patrimony 
as it can be traced back to the pioneer ideas of Charles Darwin, Louis Pasteur, and more 
recently to Alexander Oparin. During the last decades, the European community of origin 
of life scientists has organized seven out of the twelve International Conferences on the 
Origins of Life held since 1957. This community enlarged the field of research to life in 
extreme environments, including the early Earth, and to the search for extraterrestrial life, 
i.e. exobiology in its classical definition or astrobiology if one uses a more NASA-inspired 
terminology. The present contribution aims to describe the European networking activities 
in this field of research. 

2. The Science Background 

The science of exo/astrobiology, although very broad, yet forms a coherent whole crossing 
many disciplines. For example, laboratory and theoretical work on the origin of life is based 
on our understanding of the geochemical conditions of the early Earth, which in turn depends 
on conditions in the early solar system, again dependent on the chemistry of the gas and dust 
clouds between the stars. We neither know how life started on earth nor if it exists outside the 
Earth. Answering both these questions will be scientifically very exciting and also have the 
deepest meanings for philosophy and the place of humanity in the Universe. Our understand- 
ing of the early Earth is making real progress; we are finding that life can exist in extreme 
environments; there are novel ideas as to how life originates; there are real searches to find 
life outside the Earth, both on planets and moons in our own Solar System and on planets in 
other planetary systems. In the search for life outside the Earth, the discovery of water on 
Mars and of a liquid ocean on Europa, a moon of Jupiter, give us definite solar system targets, 
and the discovery in 1995 of giant planets orbiting nearby stars has revitalised the prospects 
for finding Earth-like planets which can be studied for the signature of life (Brack, 2001). 

Collaborative researches are necessarily developped in the different fields covered by 
exo/astrobiology (Westall et al., 2000; Brack et al., 2001): 

- Terrestrial life as a reference (origins of life, geological and climatic context, ingre- 
dients for primitive life, life in a test tube, diversity of bacterial life, panspermia). 


J. Seckbach et al. (eds.), Life in the Universe, 67 — 69 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


- Exploring the Solar System (Mars, Europa, Titan, Comets). 

- Search for life heyond the Solar System (exoplanets, Corot and Darwin missions). 

3. Exo/Astrobiology Networking Activities in Europe 

Because of the vastly interdisciplinary nature of the research (astronomical instrumentation, 
cosmochemistry, galactic astronomy, planetary science, solar science, atmospheric physics, 
geology, paleontology, chemistry, environmental biology, biology, information theory, phi- 
losophy, to name but some) that must be undertaken to answer the overall question of the 
origin and distribution of life, progress necessitate widespread collaborations. In the United 
States, NASA is funding the NASA Astrobiology Institute, a network of 16 lead teams, 
both to increase the funding for astrobiology and to promote interdisciplinary work. 

In Europe, several nations, e.g., Finland, France, Germany, Russia, Spain, Sweden, 
Switzerland and United Kingdom, have already established national networks. Collaborative 
links are already producing real results in Europe, such as the ROSE, Response of 
Organisms to Space Environment, consortium of ESA-funded experiments for the Inter- 
national Space Station, and the ESA Topical Team ROME on Responses of Organisms to 
Martian conditions. Within the framework of the European Commission COST Actions to 
foster cooperation in a specific research area, COST D27 “Origin of life and early evolu- 
tion” has been approved in June 2001 for a period of 5 years. The main objective of this 
action is to develop the chemistry of the origins and early evolution of life, with special 
attention to cosmochemistry, prebiotic chemistry of small molecules, directed evolution 
and origin of the genetic code. Hosted by the International Space Science Institute in Bern, 
the International Space Science Team “Prebiotic matter in space” is a consortium of 13 
scientists, each representing a specific research field crucial to revealing the origin of life 
as a consequence of the evolving Universe (Ehrenfreund et al., 2002). 

4. The European Exo/Astrobiology Network Association (EANA) 

The European Exo/Astrobiology Network Association, EANA, was created in 2001 to co- 
ordinate the different European centres of excellence in exo/astrobiology or related fields. 
The specific objectives of EANA are: 

- To bring together European researchers interested in exo/astrobiology programmes 
and to foster their cooperation. 

- To attract young scientists to this quickly evolving, interdisciplinary field of re- 

- To create a website establishing a database of expertise in different aspects of 

- To interface the Network with European bodies such as ESA, ESF, the European 
Commission and with non European institutions active in the field. 

- To popularise exo/astrobiology to the public and to students. 


The value of sharing resources on an international scale was highlighted at the Inaugural 
Meeting of the European Exo/Astrobiology Steering Group at the British National Space 
Centre, London in October 1999 and at the Strategy-oriented Meeting at CNES, Paris in 
October 2000. At these two meetings, senior representatives of the European Science Foun- 
dation and the European Space Agency acknowledged that exobiology in Europe should be 
strengthened, formalized as a Network and supported. The First European Exo/Astrobiology 
Workshop, held in Frascati, Italy, May 2001, was attended by 200 scientists. The Second 
European Workshop was organised in Graz, Austria, in September 2002. The workshop, 
attended by 320 participants, was oriented particularly to the planetology aspects of astro- 
biology, in acknowledgement of the expertise of the local organisers. The Third European 
Workshop was hosted in November 2003 by the Centro de Astrobiologia in Madrid and 
dedicated to the search for traces of life on Mars. It was attended by 260 participants. 

EANA is run by an Executive Council consisting of national members presently repre- 
senting 17 European nations active in the held, e.g. Austria, Belgium, Denmark, Finland, 
France, Germany, Hungary, Italy, Poland, Portugal, Romania, Russia, Spain, Sweden, 
Switzerland, The Netherlands, United Kingdom, on the basis of one representative per 
nation, and elected members in a number equal to the number of active nations. 

EANA is affiliated to the NASA Astrobiology Institute. The formal affiliation was signed 
in 2002 at the Graz Workshop by Rosalind Grymes, Deputy Director of NAl, during a recep- 
tion hosted by the Governor of Styria in the historical Eggenberg Castle. EANA is member 
of the Federation of Astrobiology Organizations, FAO, including the Australian Centre 
for Astrobiology (ACA), the Astrobiology Society of Britain (ASB), the Spanish Centro de 
Astrobiologia (CAB), the French Groupement de Recherche en Exobiologie (GDR Exobio), 
the American NASA Astrobiology Institute (NAI) and the Swedish Astrobiology Center 
(SWAN). The FAO has been created to facilitate international exchange between students 
and to harmonise the planning of joint astrobiology meetings. 

The EANA Web Page,, is hosted as part of the 
ESA Virtual Institute at ESA/ESTEC in Noordwijk, The Netherlands. 

5. References 

Brack, A. (2001) Life: origins and possible distribution in the Universe, In: P. Murdin (ed.) Encyclopedia Astronomy 
& Astrophysics. lOP, Bristol, pp. 1411—1421. 

Brack, A., Homeck, G., and Wynn-Williams, D. (2001) Exo/Astrobiology in Europe. Origins Life Evol. Biosphere 

Ehrenfreund, P, Irvine, W., Becker, L., Blank, J., Brucato, J.R., Colangeli, L., Derenne, S., Despois, D., Dutrey, 
A., Fraaije, H., Lazcano, A., Owen, T. and Robert, F. (2002) Astrophysical and astrochemical insights into 
the origin of life. Rep. Prog. Phys. 656, 1427-1487. 

Westall, F., Brack, A., Hofmann, B., Homeck, G., Kurat, G., Maxwell, J., Ori, G.G., Pillinger, C., Raulin, F., 
Thomas, N., Fitton, B., Clancy, P, Prieur, D. and Vassaux, D. (2000) An ESA study for the search for life on 
Mars. Planet. Space Sci. 48, 181-202. 

III. Physical Constraints on the 
Origin of Life 

Search for Efficient Chiroselective Autocatalytic Reactions 


^Centro de Investigaciones Qmmicas, Universidad Autonoma del Estado 
de Morelos, Av. Universidad No 1001, Col. Chamilpa, 62210 Cuernavaca, 
Morelos, Mexico and ^ Laboratoire des IMRCP, UMR au CNRS No 5623, 
Universite Paul Sabatier, 118, route de Narbonne, F-31062 Toulouse 
Cedex, France. 

1. Introduction 

Life is characterized by broken mirror symmetry (Palyi et ai, 1999). On the molecular 
level, proteins are composed almost exclusively of L-amino acids while nucleic acids only 
contain D-sugars. Without this chiral asymmetry, prebiotic molecular complexity leading to 
the formation of biologically active polymers could probably not have evolved (Joyce et al, 
1984; Avetisov and Goldanskii, 1991). Nevertheless, more than l '/2 century after Pasteur’s 
discovery, the origin of biomolecular chiral asymmetry is still a mystery. Meanwhile, it 
is accepted that homochirality has already appeared early during chemical evolution and 
that a homochiral molecular environment was rather a pre-condition than a consequence of 
life (Keszthelyi, 1995; Avalos etal., 2000). Parity violation (MacDermott, 1993) and other 
chiral factors such as circularly polarized light are omnipresent and can lead under favorable 
conditions to enantio-meric enrichment. However, this enhancement usually remains tiny 
and can be annihilated by long-term racemization processes. 

Hence amplifying mechanisms have to be considered that were strong and selective 
enough to recognize small enantiomeric imbalances and to overcome noise and racem- 
ization as concerned for chemical evolution scenarios. Respective theoretical model re- 
actions (Frank, 1953; Decker, 1979; Kondepudi and Nelson, 1985) can give rise to so- 
called chiral symmetry breaking, a bifurcation-like process in which the racemic state 
becomes unstable when some critical external constraints have been reached (Fig. 1). 
These approaches contribute to the perception of the nonlinear dynamics involved in 
chiral amplification but, on the other hand, remain elusive for the explicit design and 
feasibility of new laboratory experiments that can help to test the validity of the pro- 
posed hypothesis and to develop new concepts. Such studies are highly needed even if 
they are not of entire prebiotic relevance, since only experimental systems can reveal 
the richness by which nature has constructed nonlinear scenarios exhibiting the required 


J. Seckbach et al. (eds.), Life in the Universe, 1 31-11 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 




Figure 1. Sketch of a possible bifurcation scenario in a chirally autocatalytic reaction system (after Kondepudi 
and Askura, 2001). After the external constraint X has reached a critical value (Xc). the racemic state (a = 0) 
of the system becomes unstable and it evolves inevitably into an optically active state (a ^ 0). Accordingly, 
repeated experimental runs will show the transition from a monomodal (racemic) to a bimodal (optically active) 
probability distribution for a if X > Xc . 

2. Experimental Systems Showing the Presence of Possible 
Chiral Symmetry Breaking 


A number of compounds exhibit spontaneous resolution upon crystallization like binaph- 
hyl, 4,4' -dimethylchalcone, tri-o-thymotide, ethylmethylanilinium iodide, benzodiazepine, 
a-amino 8-caprolactam Ni(II) chloro complexes and sodium chlorate or bromate (Jacques 
et al, 1981). All these systems are characterized by the presence of both a “labile configu- 
ration” in solution phase and of conglomerate crystals that can serve as preferential seeds 
for later crystallization. 

A major breakthrough was reached when the role of stirring was emphasized by 
Kondepudi et al. (1990). When stirred, secondary nucleation occurs which gives rise to a 
strong chiro selective autocatalytic effect leading in each experiment to a virtually homochi- 
ral population of sodium chlorate or bromate crystals although starting from entirely achiral 
conditions. During the stirred crystallization of sodium chlorate, it was shown (Kondepudi 
et al, 1995) that the bimodal probability distribution (Fig. 1) of the crystal enantiomeric 
excess sensitively depends on the stirring rate. It is suggested that chiral symmetry breaking 
can be expected in stirred crystallization of any achiral or rapidly inter-converting com- 
pound that crystallizes in enantiomeric forms. However, for extended chiral propagation, 
it would be required that chirality will be established at a molecular state - for instance in 
asymmetric C-atoms. 


Chirally autocatalytic effects constitute the next generation of asymmetric synthesis (De 
Min et al, 1988; Feringa and van Delden, 1999). As a property of life, such processes 
could be of fundamental importance in the genesis of chiral asymmetry in nature. The first 
clearly successful reaction (1) involving a chiral autocatalyst has been reported by Soai 
et al (1995, 2000). The autocatalytic addition of diisopropylzinc ((-Pr 2 -Zn) to a prochiral 
pyrimidyl aldehyde (CHO) yielding a chiral pyrimidyl-alcohol after hydrolysis of the direct 


reaction product (COZn-/-Pr) features several important aspects. 

The system exhibits strong amplification of enantiomeric excess shown by the initial addi- 
tion of chiral alcohol or minute amounts of other chiral species like mandelic acid, [2,2]- 
paracyclophanes, helicene, octahedral cobalt complexes, deuterated chiral molecules, cir- 
cularly polarized light, photolyzed DL-leucine, chiral sodium chlorate and quartz crystals 
(Soai and Sato, 2002). Repeated experiments without chiral initiator lead to a bimodal-like 
probability distribution of e.e. (without any racemic realization) (Soai etai, 2003). The basic 
autocatalytic mechanism underlying these unprecedented properties is still subject of inves- 
tigations (Blackmond et al, 2001; Singleton and Vo, 2002; Buono and Blackmond, 2003). 

From kinetic data, a chemically reasonable tentative mechanism has been designed 
(Fig. 2) that can reproduce experimentally observed chiral amplification (Buhse, 2003). 
The model describes the underlying dynamics of the system in terms of a template-directed 
self-replication in which a dimer species, Zn-(COZn) 2 , acts as the active autocatalytic 
species. Inverse kinetic data treatment allowed us to extract the main reaction parameters 
and to predict dynamic and structural principles of this autocatalytic chiral amplification 
reaction. The dimeric chiral catalyst permits a chiroselective 3-point attachment of the 
prochiral substrate. This feature is not only important for the chiroselective action but has 
also kinetic consequences as it provides a cubic autocatalytic dynamic behavior that is the 
basis for the occurrence of bifurcation phenomena. 

Figure 2. Schematized reaction network proposed for the Soai-type autocatalytic alkylzinc addition. Strong 
cubic-type autocatalysis of the net type A 4- 2 B ^ 3 B emerges by the formation of the catalytic dimer species 
that consists of two product molecules. 


3. Conclusion 

The Soai-type reaction appears as a powerful machine to produce highly enriched chiral 
molecules in terms of a self replication-like mechanism. From this analysis, some pre- 
biotically relevant concepts can be proposed that we have designated as ‘smartness’ : 1) The 
generation of template species from two sub-units of chiral product molecules provides 
the possibility of asymmetric synthesis via 3-point attachment of a prochiral precursor. 
2) The dimerization is a fundamental process for chiral amplification because it is related 
to mutual inhibition between enantiomers. 3) Ternary organometallic complexes are able 
to provide both kinetic nonlinearity and chiral recognition from strongly asymmetrical 
interactions between the ligands. 4) The amplification of the more kinetically cooperative 
catalysts is likely to have occurred within primordial reacting systems: catalysts perform 
an autoselection through self-replication. 

4. Summary 

Chiroselective autocatalytic reaction systems provide experimental examples in which chiral 
symmetry breaking could occur. Among the few that have been already discovered, the 
autocatalytic addition of diisopropylzinc to a prochiral pyrimidyl-aldehyde yielding the 
chiral pyrimidyl-alcohol (the Soai-type reaction) appears to be the most promising. Although 
the reaction is driven far from prebiotically relevant conditions, its kinetic analysis permits 
to propose a number of concepts that can be useful for further investigations in the disputed 
domain of the origin of biomolecular homochirality. 

5. References 

Avalos, M., Babiano, R., Cintas, R, Jimenez, J.L. and Palacios, J.C. (2000) From parity to chirality: Chemical 
implications revisited, Tetrahedron: Asymmetry 11 , 2845-2874. 

Avetisov, V.A. and Goldanskii, V.L (1991) Homochirality and stereospecific activity: Evolutionary aspects, BioSys- 
tems 25, 141-149. 

Blackmond, D.G., Me Millan, C.R., Ramdeehul, S., Schorm, A. and Brown, J.M. (2001) Origins of asymetric 
amplification in autocatalytic alkylzinc additions, J. Am. Chem. Soc. 123 , 10103-10104. 

Buhse, T. (2003) A tentative kinetic model for chiral amplification in autocatalytic alkylzinc additions. Tetrahedron: 
Asymmetry 14 , 1055-1061. 

Buono, F.G. and Blackmond, D.G. (2003) Kinetic evidence for a tetrameric transition state in the asymetric 
autocatalytic alkylation of pyrimidyl aldehydes, J. Am. Chem. Soc. 125 , 8978-8979. 

De Min, M., Levy, G. and Micheau, J.C. (1988) Chiral resolutions, asymmetric synthesis and amplification of 
enantiomeric excess, J. Chim. Phys. 85 , 603-619. 

Decker, P. (1979) Spontaneous generation and amplification of molecular asymmetry through kinetical bistability 
in open systems. In: D.C. Walker (ed) Origin of optical activity in nature, Amsterdam, Elsevier, pp. 109-124. 

Feringa, B.L. and van Delden, R.A. (1999) Absolute asymmetric synthesis: The origin, control, and amplification 
of chirality, Angew. Chem. Int. Ed. 38, 3419-3438. 

Frank, FC. (1953) On spontaneous asymmetric synthesis, Biochim. Biophys. Acta 11 , 459^63. 

Jacques, J., Collet, A. and Wilen, S.H. (1981) Enantiomers, Racemates and Resolution, J. Wiley, New York. Joyce, 

G.F., Visser, G.M., van Boeckel, C.A.A., van Boom, J.H., Orgel, L. and van Westrenen, J. (1984) Chiral selection 
in poly(C)-directed synthesis of oligo(G), Nature 310 , 602-604. 

Keszthelyi, L. (1995) Origin of the homochirality of biomolecules. Quart. Rev. Biophys. 28 , 473-507. 

Kondepudi, D.K. and Nelson, G.W. (1985) Weak neutral currents and the origin of biomolecular chirality. Nature 
314 , 438^41. 


Kondepudi, D.K., Kaufman, R. and Singh, N. (1990) Chiral symmetry breaking in sodium chlorate crystallization, 
Science 250 , 975-977. 

Kondepudi, D.K., Bullock, K.L., Digits, J.A. and Yarborough, RD. (1995) Stirring rate as a critical parameter in 
chiral symmetry breaking crystallization, J. Am. Chem. Soc. 117 , 401^04. 

Kondepudi, D.K. and Asakura, K. (2001) Chiral autocatalysis, spontaneous symmetry breaking, and stochastic 
behavior, Acc. Chem. Res. 34 , 946-954. 

MacDermott, A.J. (1993) The weak force and the origin of life. In: C. Ponnamperuma and J. Chela-Flores (eds.) 
Chemical evolution: Origin of life, Hampton, Deepack Publishing, pp. 85-99. 

Palyi, G., Zucchi, C. and Caglioti, L. (eds.) (1999) Advances in BioChirality, Elsevier, Amsterdam. 

Singleton, D.A. and Vo, L.K. (2002) Enantioselective synthesis without discrete optically active additives, J. Am. 
Chem. Soc. 124 , 10010-10011. 

Soai, K., Shibata, T, Morioka, H., Choji, K (1995) Asymmetric autocatalysis and amplihcation of enantiomeric 
excess of a chiral molecule. Nature 378 , 767-768. 

Soai, K., Shibata, T. and Sato, I. (2000) Enantioselective automultiplication of chiral molecules by asymmetric 
autocatalysis, Acc. Chem. Res. 33, 382-390. 

Soai, K. and Sato, I. (2002) Asymmetric autocatalysis and its application to chiral discrimination, Chirality 14 , 

Soai, K., Sato, I., Shibata, T., Komiya, S., Hayashi, M., Matsueda, Y, Imamura, H., Hayase, T., Morioka, 
H., Tabira, H., Yamamoto and Kowata, Y. (2003) Asymmetric synthesis of pyrimidyl alkanol without adding 
chiral substances by the addition of diisopropylzinc to pyrimidine-5-carbaldehyde in conjunction with asym- 
metric autocatalysis. Tetrahedron: Asymmetry 14 , 185-188. 



Department of Applied Chemistry, Department of Physics, Peking 
University, Beijing 100871, China 

Abstract. Salam hypothesis was elaborated in the First Trieste Conference on Chemical Evolu- 
tion. We spent twelve years on a number of experiments (i.e. temperature-dependence of X-ray 
diffraction, neutron diffraction, atomic force microscopy of the surface structure, specific heat 
measurement, DC and AC magnetic susceptibilities, longitudinal ultrasonic attenuation and 
velocity, *H CRAMPS and '^C CP/MAS solid state NMR studies, Raman spectra & natural 
optical rotation) to verify the second-order phase transition and the role in amino acids. The 
configuration transformation from D- to L-type was refuted by gas chromatographic anal- 
ysis of Chirasil-Val capillary column of DL, D- and L-valine. This paper focuses attention 
on the role of phase transition in amino acid, which might play a bifurcation-type mecha- 
nism in a chirally-pure state instead of a direct configuration change from D- to L-amino acid 
below Tc- 

1. Introduction 

The homochirality of natural amino acids and sugars remains a puzzle for theories of the 
chemical origin of life (Bada, 1995, Meiiring, 1987, Mason, 1985). The cause for the 
homochirality of biologically relevant molecules is assumed to be the intrinsic chira- 
lity present at the elementary particle level (Kondepudi 1985, Quack 1989). The idea 
started with the possibility of defining a science of life based on atomic physics. Salam 
(1991,1992) proposed the subtle energy difference of chiral molecules induced by 7? inter- 
actions in terms of quantum mechanical cooperative and condensation phenomena, which 
could give rise to second-order phase transitions (including D to L transformations) below 
a critical temperature Tc. The value of Tc is around 250K deduced from Ginzberg-Landau 

Bonner (2000) and L. Keszthelyi (2001) have discussed the extraterrestrial origin of the 
homochirality of biomolecules and the amplification of tiny enantiomeric excess. Attention 
is called upon the mechanism for production of extraterrestrial handedness based on Salam’s 
condensation hypothesis. Figureau et al. (1995) reported that their experiments have failed 
to validate Salam’s predicted phase transitions. A recent report by Compton et al. (2003) 
presented arguments against the Salam hypothesis in terms of their observing small feature 
in the experiments. 


J. Seckbach et al. (eds.), Life in the Universe, 79 - 82 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Experimental 


Elemental analysis of C, H and N of D-/L-alanine single crystals showed that D-/L-alanine 
were pure single crystals without crystal water, and the crystals of D-/L- alanine were 
determined by X-ray diffraction crystallography at 300K, 293K, 270K, 223K, 250K and 
D-valine was measured at 293K, 270K, 223K and 173K (Wang, 2003). 


In previous work, a number of experiments were designed to search for the parity violation 
of the electroweak force at the phase transition of single crystals of D- and L-alanine and 
valine. An obvious second-order phase transition was shown in specific heat measurements 
of D- and L-valine by the differential scanning calorimeter. The phase transitions were 
reversible and reproducible. The differential peak was shown to be on the order 6.5 x 10“® 
eV/ molecule • K = d ACp/dT = d AE/jy/dT which was reflected in the slope difference of 
two A Cp vs T curves of D- and L-valine at 7). (Wang, 2000). 

Magnetisation measurements on a SQUID showed a difference in the magnetic suscepti- 
bility (xp) as a function of temperature between the D- and L-alanine. DC and AC magnetic 
susceptibility measurements proved that the electron spin of ct-H atom of D-/L-alanine is 
in a certain direction only in DC magnetic field. We sfudied fhe temperature dependence of 
AC mass susceptibility which showed that the curves Xp vs T of both D-/L-alanine were 
horizontal without discontinuity (Wang et al. 2002). Based on the above experiments, we 
conjectured that the electron spin of a-H in D-alanine (D-valine) causes a flip at 7). by de- 
creasing the hydrogen atom’s total spin from one to zero then released the energy 6 x 10“® 
eV. It coincides with the measured parity-violating energy difference 6.2 x 10“^ eV at Tc 
of valine (Rith et al. 1999). 

The temperature-dependent DC-magnetic susceptibilities of D-/L-alanine show a con- 
trary parity-violating role and bifurcation mechanism from 250 to 200K (Fig. 1). 

^H CRAMPS ssNMR was performed to study the temperature-dependent proton nuclei 
dynamics of D-/L-alanine and found that a-H nucleus is the active center in the parity- 
violating phase transition (Wang et al., 2003). 

3. Results and Discussion 

Our experimental results support Salam prediction of second-order phase transition involv- 
ing dynamic symmetry breaking as an amplification mechanism. Salam proposed that a-H 
atoms give up their loose electrons and act as metallic hydrogen under Tc which was verified 
in ^H CRAMPS ssNMR measurements of alanine and valine. Zanasi et al. (1998) have cal- 
culated the parity-violating potential of valine enantiomers (—16.525 Hartree) which 
was larger than that of alanine enantiomers (—12.318 Hartree). The higher PVED values 
result in an increase of 7^ in Salam model (Buschmannef a/., 2000; Zanasi et al., 1999). The 





■ •• 

• * ■ 

• • • • 





1 .^ 

200 220 240 260 280 300 


Figure 1. Temperature dependence of magnetic susceptibility at a field of (a) 1 .0 T (b) — 1 .0 T . 

transition temperature shift is observed in 'H CRAMPS ssNMR. The Tc of valine is around 
270K and that of alanine around 250K. A bifurcation-type mechanism in a chiraly-pure 
state is preferred to a direct configuration change from D- to L-amino acid at the critical 

4. Acknowledgments 

This research was supported by the grant of NSFC (20310202026). 

5. References 

Avalos, M., Babiano, R., Cintas, R, Jimenez, J. L. and Palacios, J. C. (2000) From Parity to chirality: chemical 
implications revisited, Tetrahedron: Asymmetry. 11, 2845-2874. 

Bada, J. L. (1995) Origins of homochirality, Nature 374, 594-595. 

Bonner, W.A. (2000) Parity violation and the evolution of biomolecular homochirality, Chirality 12, 1 14-126. 

Buschmann, H., Thede, R. and Heller, D. (2000) New developments in the origins of homochirality of biological 
relevant molecules, Angew. Chem. Int. Ed. 39, 4033^036. 

Sullivan, R., Pyda, M., Pak, J., Wunderlich, B., Thompson, J.R., Pagni, R., Pan, H., Barnes, C., Schwerdtfeger, P. 
and Compton, R. (2003) Search for electroweak interactions in amino acids crystals. II. The Salam Hypothesis, 
J. Phys. Chem. A 107, 6674-6680. 

Figureau, A., Duval, E. and Boukenter, A. (1995) Can biological homochirality result from a phase transition? 
Orig Life Evol. Biosphere 25, 21 1-217. 

Kondepudi, D. K. and Nelson, G. W. ( 1 985) Weak neutral currents and the origin of biomolecular chirality. Nature 
314, 438^41. 

Keszthelyi, L. (2001) Homochirality of biomolecules: Counter-arguments against critical notes. Origins of Life 
and Evolution of the Biosphere 31, 249-256. 

Mason, S. (1985) Origin of biomolecular chirality, Nature 314, 400^01. 

Meiring W. J. (1987) Nuclear p-decay and the origin of biomolecular chirality. Nature 329, 712-714. 

Quack, M. (1989) Structure and dynamics of chiral molecules, Angew. Chem. Int. Ed. Engl 288, 571-589. 

Rith, K. and Schafer, A. (1999) The mystery of nuclear spin. Scientific American, 58-63. 

Salam, A. (1991) The role of chirality in the origin of life, J. Mol. Evol. 33, 105-1 13. 

Salam, A. (1992) Chirality, phase transitions and their induction in amino acids, Phys. Lett. B. 288, 153-160. 


Wang, W. Q., Yi, R, Ni, Y. M., Zhao, Z. X., Jin, X. L. and Tang, Y Q. (2000) Parity violation of electroweak force 
in phase transitions of single crystals of D- and L-alanine and valine, J. Biol. Phys. 26 , 51-65. 

Wang, W. Q., Min, W., Bai, R, Sun, L„ Yi, R, Wang, Z. M., Yan, C. H., Ni, Y. M. and Zhao, Z. X. (2002) Temperature- 
dependent magnetic susceptibilities study on parity-violating phase transition of D- and L-alanine crystals. 
Tetrahedron: Asymmetry 13 , 2427-2432. 

Wang, W. Q., Min, W., Liang, Z., Wang, L.Y, Chen, L. and Deng, R. (2003) NMR and parity violation: low- 
temperature dependence in ^ H CRAMPS and C CP/MAS ssNMR spectra of alanine enantiomer, ’ Biophysical 
Chemistry 103 , 289-298. 

Wang W. Q., Gong, Y, Wang, Z. M. and Yan, C. H. (2003) Crystal structure of D-alanine at the temperature of 
293, 270, 223 and 173K, Chinese J. Struct. Chem. 22 ( 5 ), 539-543. 

Zanasi, R. and Lazzeretti, P. (1998) On the stabilization of natural L-enantiomers of a-amino acids via parity- 
violating effects, Chem. Phys. Lett. 286 , 240-242. 

Zanasi, R., Lazzeretti, R, Ligabue, A. and Soncini, A. (1999) Theoretical results which strengthen the hypothesis 
of electroweak bioenantioselection, Phys. Rev. E 59 , 3382-3385. 

The Role of Proton Gradient and High Temperature in the Polymerization 
of Amino Acids Embedded in Bilayers 


^Centro de Biotecnologia. Fundacion Instituto de Estudios Avanzados, AP 
17606, Parque Central. Caracas 1015-A, Venezuela. ^ Departamento de 
Estudios Ambientales. Universidad Simon Bolivar, Caracas-Venezuela. 

^ Departamento de Quimica. Universidad Simon Bolivar, 
Caracas-Venezuela. ^ Departamento de Biologia Celular. Universidad 
Simon Bolivar, Caracas-Venezuela. 

1. Introduction 

The first living organisms were not necessarily the result of the assembly of fully struc- 
tured biochemical mechanisms involving macromolecules, but at least some life-related 
processes, as we know them today, probably appeared alongside the structural integration 
and early evolution of these proto-organisms. Along these ideas, we consider that spatial 
compartmentalization and protein functionality are tightly related in their origin. A possi- 
ble scenario of this relationship is the early polymerization of amino acids (AA) embedded 
in amphiphilic membranes. The resulting membrane-embedded proto-proteins could have 
played an important role modulating the transport of elements or ions between the internal 
compartment and the environment. This scenario is congruent with selectivity arguments of 
AA (Hitz & De Luisi, 2000) (i.e., 20 out of nearly 70 originally available (Croning & Chang, 
1993; Engel & Nagy, 1982)) and their homochirality (Hitz et al., 2001). Other mechanisms 
of peptide bond formation, such as alumina-catalyzed reactions (Bujdak & Rode, 2002), 
polymerization on clay surfaces (Bujdak & Rode, 1996) and polymerization mediated by 
thioesters (De Duve, 1996), can also lead to this scenario. 

In this paper we present theoretical evidence that supports the possibility of polymer- 
ization of AA embedded in amphiphilic membranes by means of non-equilibrium, ion flux 
mechanism, totally independent of any DNA-mediated process. 

2. Non-Equilibrium Fluxes Between Compartments 

Our model is a system formed by two aqueous environments, namely the “inside” of the 
closed amphiphilic membrane, and the outside or “environment”, with proton concentrations 
C'^ and respectively. A bilayered membrane of thickness Ax separates these envi- 
ronments. AA at a concentration Caa are embedded in this membrane. In order to allow 
the amino acid polymerization to take place, the system is displaced from equilibrium, 


J. Seckbach et al. (eds.), Life in the Universe, 83 - 87 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


as occurs with the dynamics state of other living processes (e.g. Nicolis & Prigogine 

We want to know if a simple entropic coupling is enough to displace the polymerization 
reaction affinity, A, toward the polymerization of AA. To test our hypothesis, we consider 
the near-equilihrium equations (De Groot, 1968) for the fluxes in our system: 



Lw dCu 

T dx 
Lch . 



Li dCn 
T dx 
Lh dCn 


( 1 ) 

( 2 ) 

( 3 ) 

In these equations, Jq denotes the proton {q — H) and water {q — w) fluxes, both perpen- 
diculars to the membrane’s surface. Jch denotes the chemical flux. The quantities Li are 
the phenomenological coefficients (De Groot, 1968), and T is the absolute temperature. 
We constrain the system to the concentration difference between inside and environment 
through boundary conditions, and we let free and to relax under the constraints. 
Following the law of minimum local entropy production (De Groot, 1968), our system 
attains a stationary state when 

dCn , dC^ 
dx dx 

A = 0 

( 4 ) 

( 5 ) 

The proton concentration prohle is obtained by considering equations (5) and (2), and 
the boundary conditions Cff(O) = C‘^ and Ch{A.x) = C^”: 

Ch(x) = + ^x ( 6 ) 

with ACh = — Cp . Replacing equation (4) into (1), leads to a constant distribution 

of water molecules, whose value is determined by the physical properties of the membrane. 
For a completely hydrophobic membrane, we have C^ix) = 0. 

3. Equilibrium Displacement of the Condensation Reaction 

The polymerization reaction of the AA is of the form 

P + P P 

1 n 1 rn l m . 


( 7 ) 

in which 7\ denotes an oligopeptide consisting of k AA residues. The quantities Kc and 
Kf are the condensation and fragmentation constants, independent of polymer size k. 
Following the Blatz-Tobolsky ( 1 945) model for reversible polymerization, we can determine 
the net concentrations of peptidized residues by measuring the quantity of peptide bonds: 
Pg — ^{k — l)Cpj, and reactive groups (i.e., either N-term or C-term): Cr — Cp^\ 

Cr — —Ch — —-KcCnCji 

-KfCu, Cr, 

( 8 ) 


Figure 1. Proton flux (left) across the membrane rapidly atttains a stationary state determined by the pH 
difference across the membrane. Water (center) is initially produced by the polymerization reaction, but later it 
is eluted by diffusion. The chemical flux (right) attains a stationary state without chemical production, resulting 
from the limited number of AA able to polymerize. 

Assuming that Caa is constant, the equilibrium point of the process in equation (8) is 

2 Ch(xo) I 2 Ch(xo) V 2 Ch(xo) Jj 

in which the concentrations C^ixo) and Ch(xo) are those of the stationary state. 

4. Discussion 

In this model, the proton flux between the inside and the environment rapidly attains a 
stationary state and the proton concentration increases linearly from the inside to the envi- 
ronment (fig. 1). During the first stages of the process, the flux of water increases as a direct 
consequence of the synthesis of water molecules from the condensation reaction. Later, the 
molecules of water elute to the environment. At the stationary state of the system the flux 
of water is null. The results of a simulation (fig. 2) demonstrate that the stationary state of 
the chemical equilibrium corresponds to a null chemical flux. Since the membrane is totally 
hydrophobic, and the stationary concentration of water is zero, the displacement of the 
chemical affinity is maximum. Hence, the displaced reaction always reaches a stationary 

Figure 2. Stationary concentration profiles (in arbitrary units) of the four chemical species. AA and peptides 
are embedded at xg = 2/3 nm from the inner membrane’s interface. 


state in which all AA are polymerized since the number of all available reactive groups 
decreases to zero, i.e. following equation (9) Cb — Caa- This stationary distribution is 
attained regardless of the value of Kf. 

The chemical rate theory (Hanggi et ah, 1990) states that the velocity of reaction is 
K = K exp( AG*//?r), where AG* is the energy of the transition state. In a non-equilibrium 
process, this transition energy is not the same as that in an equilibrium process, thus AG* 
is determined by the solution of the corresponding Boltzmann equation (Hanggi et ah, 
1990). The proton flux and the collision rate between protons and AA are high, for what 
AG* decreases. This results in a fast-reacting system able to attain fully condensed AA 
in relative short times. In our model, K is reduced by increasing the collision rate and by 
increasing temperature. For this reason, our model is even more plausible in environments 
with high temperatures (Kasting, 1993; Rohlhng, 1976) or moderately high temperatures 
(i.e., below 100 °C) (Miller & Lazcano, 1995), such as those abundant scenarios in which 
the origin of life might have occurred. 

5. Conclusions 

We have presented theoretical evidence that supports the possibility of polymerization of 
AA embedded in membranes by means of a mechanism based on non-equilibrium fluxes: a 
maintained proton flux and a constant eflux of water, coupled with the vanishing chemical 
affinity, displaces the chemical equilibrium toward AA condensation. The process leads to 
the polymerization of all the A A embedded in the membrane, regardless of the value of the 
fragmentation constant Kf. Hence, the reaction results in a large number of oligopeptides. 
Systems with these properties allow linking chemical and biological evolution, since vesicles 
mixtures with diverse polymers on their surface become a rich scenario on which natural 
selection can act. 

6. References 

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Phenomena, J. Phys. Chem. 49, 77-80. 

Bujdak, J. and Rode, B.M. (2002) Preferential amino acid sequences in alumina-catalyzed peptide bond formation, 
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Bujdak, J. and Rode, B.M. (1996) The Effect of Smectite Composition on the Catalysis of Peptide Bond Formation, 
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De Duve, C. (1996) Vital Dust, Basic Books, New York, USA. 

De Groot, S.R. (1968) Thermodynamics of Irreversible Processes, North-Holland Publishing Co., Amsterdam, 

Engel, M.H. and Nagy, B. (1982) Distribution and enantiomeric composition of amino acids in the Murchinson 
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62, 251-342. 

Hitz, T., Blocher, M., Walde, P, and Luisi, P.L. (2001) Stereoselectivity Aspects in the Condensation of Racemic 
NCA- Amino Acids in the Presence and Absence of Liposomes, Macromolecules 34, 2443-2449. 


Hitz, T. and Luisi, P.L. (2000) Liposome-Assisted Selective Polycondensation of a-Amino Acids and Peptides, 
Biopolymers 55, 381-390. 

Kasting, J.F. (1993) Earth’s Early Atmosphere, Science 259 , 920-926. 

Miller, S.L. and Lazcano, A. (1995) The origin of life — did it occur at high temperatures? J. Mol. Evol. 41 , 

Nicolis, G. and Prigogine, I. (1977) Self-Organization in Nonequilibrium Systems: From Dissipative Structures to 
Order through Fluctuations, Wiley-Interscience, New York, USA. 

Rohlfing, D.L., (1976) Thermal Polyamino Acids: Synthesis at Less Than 100 °C, Science 193 , 68-70. 



^Dept. Biologia Geral, Inst. Ciencias Biologicas, Univ. Federal Minas 
Gerais, Belo Horizonte MG 31270-901 Brasil, ^Dept. Matemdtica, Inst. 
Ciencias Exatas, Univ. Federal Minas Gerais, Belo Horizonte MG 
30123-970 Brasil 

Abstract. A model for the genetic code structure and organization is presented. It is self- 
referential due to starting without an mRNA to be translated. Recruitment of tRNAs occurs 
in pairs, one fishing the other, their anticodons being simultaneously codons for each other. 
Genes - mRNAs - arise in the process of formation of the code. It is also functional, depicting 
various consistent correlations with protein properties. First attributions - Gly, Pro, Ser - are 
the outliers from the hydropathy correlation, protein-stabilizing and RNA-binding amino acids. 
These properties allow formation of a stable RNP system, the source-product relationship being 
established. The succession of entries also obeys the following criteria: (a) synthetases class II 
to class I; (b) protein conformations from aperiodic to helices and then strands; (c) ordering of 
protein sequences with heads and tails, respectively, stable and unstable, called a non-specific 
punctuation system, in the second stage; (d) DNA-binding amino acids in the third stage; 
(e) late development of the specific punctuation system, that of initiation defining the stop 
signs, and (f ) of the hexacodonic expansions of Leu and Arg. 

I. Introduction 

A model for the structure of the genetic code is presented, describing how the matrix was 
formed and organized. 

This work had a first presentation in Guimaraes (1996) and a description of the first 
stages in Guimaraes and Moreira (2002). A concise account of the full model (Guimaraes 
and Moreira, 2004) is shown here. 

2. Self-reference and Function 

The model is based on successive recruitment of pairs of anticodons of the palindromic 
type - with the same bases at the extremities (Table I). 

It is indicated that the triplets AGA : UCU fished each other while Ser was octacodonic, 
before concession of Y CU to Arg, and that the coherence of synthetases class I for Gin and 
Val was established after concession of Y UG to Gin. 


J. Seckbach et al. (eds.), Life in the Universe, 89 - 91 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


TABLE 1. Anticodon pairs and synthetase class couples. 
pDiN underlined, stages numbered with letter indices, 
classes in Roman numerals. 

AAA Phe 
UUU Lys 
II : II 

(both atypic) 

AGA Ser 
UCU Ser 
I b 

ACA Cys 
UGU Thr 
I: II 

4 a 

GAG Leu 

GGG Pro 

GCG Arg 

GUG His 



CGC Ala 

CAC Val 


I a 



I : I 


I: II 



In Stage 1 the system is entirely self-referential - anticodons in a pair are simultaneously 
codons for each other - and there is no need for an mRNA to be translated. 

In Stage 2, mRNAs are formed and structured, with heads and tails (non-specihc punc- 
tuation; Guimaraes, 2001). So, genes (mRNAs) are formed and dehned concomitantly with 
formation of the coding system, when the proteins (now ‘products’) feed back upon the 
RNAs, through binding to them and stabilizing the nucleoproteins. Thereafter, the system 
developed auto-catalytic features. 

The model is also functional, due to the consistency with various other protein properties. 
Stage 3 contains the amino acids most characteristic of DNA-binding motifs. The specihc 
punctuation system and the hexacodonic expansions of Leu and Arg are placed in Stage 4. 

Besides the characters specified, note the trajectories: from the GC-rich core to the 
periphery of the matrix; from synthetases class II to I, and the consistency with amino 
acid biosynthesis derivations. Sectors of pDiN are self-contained, the only cross-sector 
attribution being the hexacodonic Arg (Figure 1). 

+AA Phe (2 b) 
Leu (4 c) 

+GA Ser (1 b) 

+CA Cys (3 c) 


X (4 b) 

-bUA Tyr (4 a) 

X (4 b) 

+AG Leu (2 a) 

+GG Pro (la) 


+CG Arg (3 a) 


+UG His (3 b) 


+AC Val (3 b) 

+GC Ala (3 a) 

+CC Gly (1 a) 

+UC As (2 a) 


+AU lie (4 a) 


f Met (4 b) 

+GU Thr (3 c) 

+CU Ser (1 b) 

Arg (4 c) 

+UU Asn (2 b) 

Figure 1. Formation of the genetic anticode. Bases in hydrophilicity A-G-C-U order. Sectors of principal 
dinucleotide (pDiN) types: mixed (Mx; quadrants -|-RY : +YR) and homogeneous (Ho, bold; +RR : +YY); 
+, the 5' bases. Stages numbered with letter indices, in parenthesis. The amino acids in parenthesis are indicated 
to be previous occupiers of the respective boxes. Further explanations in the text. 


3. Stages 

Stage 1: (1 a) Gly +cc:+gg 5 ^^. +ga:+cu 

The sector of Ho pDiN (quadrants: +RR : +YY) starts being filled. Amino acids are 
protein-stabilizers, RNA-binders and characteristic of coils and turns of proteins. Attribu- 
tions are the outliers of the hydropathy correlation. All synthetases are class II. Gly may 
have preceded Pro in the -l-GG box, since Pro is derived biosynthetically from Glu. 

Stage 2: (2 a) Asp then Glu Leu, (2 b) Asn then Lys Phe. 

The hydropathy correlation is established. Synthetases make one couple of class 1 and 
the atypical couple: Lys class II, but class I in some organisms; Phe class II, but acylating 
in the class 1 mode. 

Non-specific puncfuation and mRNA strucfure are formed: amino acids of Stage 1 
become heads of proteins, those of Stage 2 added as tails. Enter 3/8 of the amino acids of 
the set of protein helix-forming, 1 /7 of the strand-forming. 

Stage 3: (3 a) Ala +gc:-hcg ^j.g^ (3 His then Gin +ug:-hac ^3 +gu:-hca 
Cys then Trp. 

Start the sector of mixed pDiN (quadrants: -|-RY : -|-YR). Amino acids are characteristic 
of DNA-binding motifs. Synthetases make one class I couple (Gin / Val) and the two couples 
of different classes - among the 8 pairs of boxes. Ala may have preceded Arg in the -fCG 
box, which is a simpler alternative to other proposals for the predecessor to Arg. 

Stage 4: 

(4 a) lie then Met Tyr. All synthetases are class 1. 

(4 b) The specific punctuation system is formed: fMet with slipped pDiN CA U and 
codons -L UG ; X anticodons UC^ and YUA, pairing with the initiation codon, thereby 
competing with fMet, are deleted. 

(4 c) The hexacodonic expansions of Leu and Arg synthetases class I, respectively, into 
Y AA and YCU, are formed, driven by codon usage. 

4. Acknowledgments 

Support from CNPq and FAPEMIG to Romeu Cardoso Guimaraes. 

5. References 

Guimaraes, R.C. (1996) Anticomplementary order in the genetic coding system, Abstracts of the International 
Conference on the Origin of Life, ISSOL, Orleans, 11: 100. 

Guimaraes, R.C. (2001) Two punctuation systems in the genetic code. In: J. Chela-Flores, T. Owen and F. Raulin 
(eds.) First Steps in the Origin of Life in the Universe, Kluwer, Dordrecht, pp. 91-94. 

Guimaraes, R.C. and Moreira, C.H.C. (2002) Genetic code structure and evolution: aminoacyl-tRNA synthetases 
and principal dinucleotides, In: G. Palyi, C. Zucchi and L. Caglioti (eds.) Fundamentals of Life, Elsevier, 
Paris, pp. 249-276. 

Guimaraes, R.C. and Moreira, C.H.C. (2004) The functional and self-referential genetic code. In: G. Palyi, C. 
Zucchi and L. Caglioti (eds.) Progress in Biological Chirality, Elsevier, Oxford, pp. 83-118. 



^Institute de Ciencias Nucleares, UNAM, A.P. 70-453, Mexico, D.F. and 
^D. Gral. Divulgacion de la Ciencia, UNAM. A.P. 70-487, Mexico D.F. 

Abstract. The emergence of life needed a physical and chemical preamble. There is a large 
variety of experimental data to support the hypothesis for the abiotic formation of organic 
compounds. Although much knowledge has been obtained, many questions remain. One im- 
portant factor in chemical evolution is related to the importance of random chemical synthesis 
versus more selective pathways forming compounds of biological relevance. Biased synthesis 
mechanisms would induce a much smaller space sequence in comparison to a space sequence 
derived from a purely random synthesis. Such condition in turn would render more feasible 
the emergence of a chemical system compatible with life. 

In this paper we exemplify a biased synthesis that could have been relevant in primitive 
scenarios. We perform experiments simulating an organic compound adsorbed in soil and 
exposed to an energy source. Carboxylic acid is adsorbed in a clay mineral and is exposed 
to radiation. The chemical reaction induced in this system follows a preferential pathway of 
decomposition over others; both solid surfaces and radiation play an important role. 

I. Introduction 

In the study of the origin of life it is important to consider three facts. (1) There is life 
on Earth. (2) There is only one kind of life on the Earth: The central machinery in all 
organisms is built out of the same set of molecular components. Therefore, all known 
living things are rooted to a common ancestor. (3) Even the simplest living systems are 
highly organized and very complex (Cairn-smith, 1985). This may suggest that somehow 
the chemical components that formed a primitive chemical system compatible with life 
were fairly abundant. On the other hand, how could it be so if plausible prebiotic synthesis 
shows a variety of chemical products? Eor instance, if we analyzed a chemical reaction 
that goes randomness, it may form (a) by-products, (b) structural isomers and, (c) optical 
isomers. They decrease the yield of a specific compound. It is important then to explore 
chemical mechanisms able to narrow the variety of prebiotic chemical compounds liable to 
be used in the construction of primitive living systems. 

In this work, we emphasize the importance of biased synthesis in prebiotic chemistry 
for the formation of biological molecules to reproduce a narrow set of monomers. We study 
a simple chemical system: a carboxylic acid adsorbed in a clay mineral and exposed to 


J. Seckbach et al. (eds.), Life in the Universe, 93 — 96 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Our interest is twofold; (1) to show experimentally that biased synthesis might have 
occurred in geologically relevant conditions on the primitive Earth. (2) To evaluate the role 
that a solid surface plays to induce biased reaction. 


Despite the importance of gas and solution phase reactions in prebiotic monomer synthesis, 
it is difficult to envision the synthesis of complex macromolecules and their assembly into 
proto-cells without a multiphase system. Solid phase contribution is of great relevance to 
the experimental simulation of the prebiotic Earth (Ramos-Bernal and Negron-Mendoza, 
1998). The most geologically relevant solid surfaces to promote chemical reactions on the 
primitive Earth were clays. They have several roles: (1) Adsorption of monomer that causes 
highly concentrate systems. (2) They facilitate condensation and polymerization reactions. 
(3) They have a surface that may serve as template for specific adsorption and replication 
of organic molecules. 

To induce chemical reactions in these surfaces it is important to consider the energy 
source. In multiphase systems this source needs to be available, abundant and efficient to 
promote chemical reactions. Natural energy sources such as radioactive decay, cavitation 
and triboelectric energy (i.e., energy of mechanical stress) may have a great importance in 
those multiphase scenarios. This importance is due that they are penetrating energy sources 
(Negron-Mendoza et al., 1996). 

2. Experimental Procedures 

The experimental part is divided in two stages: (1) radiolysis of aqueous solutions of the 
carboxylic acid, and (2) study of the radiolysis of the water-carboxylic acid-clay system. 

The carboxylic acids studied were malonic, succinic, acetic and aconitic acids, all re- 
lated to metabolic pathways. The solid surface was sodium montmorillonite of Wyoming 
bentonite. The aqueous solutions of carboxylic acids were 0. 1 M, at natural pH. The oxygen 
was removed by passing argon through the solutions. The irradiations were carried out in a 
gamma source. The radiation doses were from 46 to 300 kGy. 

Samples with clay. One hundred milligrams of clay were mixed with 3 ml of the acid 
0. 1 M; this amount is below the cation exchange capacity of the clay. The samples were 
adjusted to pH 2, and they were shaken for 60 minutes. After this time, the samples were 
irradiated as described above. After irradiation, the sample was centrifuged and the su- 
pernatant was removed and analyzed by GC. A measured amount of the supernatant was 
evaporated until dryness. Methyl esters were then prepared according to Negron-Mendoza 
et al., 1983. The analysis was done by gas chromatography and GC-mass spectrometry. 

3. Results and Discussion 

The irradiation of aqueous carboxylic acid produced many compounds. The central feature 
of these series of experiments was the production of the acid dimer, as the main way of 


TABLE 1 . Products Formed from the Irradiation of Aqueous Carboxylic Acids. 


reaction without 

Main products 

Principal reaction 
with clay 

Main products 



Succinic acid 


Methane, CO2 



Tricarballylic and citric 


Itaconic acid, CO2 



Succinic and 

carboxysuccinic acids 


Acetic acid, CO2 



Succinic dimer 


Butanoic acid, CO2 

decomposition of the targeted compound. For example, in the radiolysis of acetic acid, 
the main product was succinic acid, the dimeric product. The decomposition of the target 
compound increased as a function of the dose. 


In presence of clay the number of products identified decreased considerably. The main 
pathway of decomposition was a decarboxylation reaction; this is the loss of a carbon atom 
as CO2. The production of the dimer decreased as a function of the dose. 

Gaseous products were also detected and identified in all the systems under study: CO2 
and H2. The production of CO2 was greater in samples with clay. Its formation increased as 
function of the dose. The source of H2 was the radiolysis of water and from the abstraction 
reactions produced during the radiolysis. Table 1 summarized the main results. 

The results showed that the radiolysis of the clay-acid system follows a defined path 
rather various. The main lane of decomposition was the decarboxylation of the target com- 
pound rather than condensation/dimerization reactions. 

4. Discussion and General Remarks 

In an aqueous system the radiation interacts with the water molecules. Very reactive species 
are formed by this interaction (H, OH, Caq, H2 and H2O2). These attack in a secondary way 
to the carboxylic acid molecules, yielding the observed products. 

In the systems without clay, the main reactions induced by radiation take place via free 
radicals. The main reaction was the dimerization. In contrast, in presence of clay, the results 
showed that there are changes in the mechanism. First, the number of products diminishes 
and the generation of CO2 increases lineally with the radiation dose. Thus, the main reaction 
is the decarboxylation and products obtained are CO2 and the corresponding acid with one 
carbon atom less than the targeted compound. 

The present study represents a further attempt to gain more insight into the role-played 
by radiation-induced reactions in solid surfaces in chemical evolution studies. As in previ- 
ous studies (Negron-Mendoza and Ramos-Bemal, 1998 ), the results obtained suggest that 
the clay alter the reaction mechanism in a preferential way for some reactions, acting as 
moderator in energy transfer process. 


We have showed experimentally that radiation-induced reactions in carboxylic acids are 
an example of preferential synthesis, while adsorbed in a solid surface. The radiolysis of 
the clay-acid system goes along a definitive path (oxidation) rather than following several 
modes of simultaneous decomposition. This behavior is important for prebiotic synthesis 
because solid surfaces can drive the reaction in a preferable path. These experiments prove 
that non-random products are produced under plausible prebiotic conditions, and in the 
presence of clay unequal or biased probability of reactions appear. This work was partially 
supported by a grant IN 115501-3. 

5. References 

Caims-Smith, A.G. (1985) Seven Clues to the Origin of Life Cambridge University Press, London pp. 4—6. 
Negron-Mendoza, A., Albarran, G. and Ramos-Bemal, S. (1996) Clays as natural catalyst in Prebiotic Processes, 
In: J. Chela-Flores, and F. Raulin (eds.) Chemical Evolution: Physics of the Origin and Evolution of Life, 
Kluwer Academic Publishers, Dordrecht, pp. 97-106. 

Negron-Mendoza, A. and Ramos-Bemal, S. (1998) Radiolysis of Carboxylic Acids Adsorbed in Clay Minerals. 
Radiation Physics and Chemistry. 52, 395-397. 

Ramos-Bemal S. and. Negron-Mendoza, A. (1998) Surface Chemical Reactions During the Irradiation of Solids: 
Prebiotic Relevance. Viva Origino 26, 169—176. 


Geophysical Institute, University of Alaska- Fairbanks 
Fairbanks, AK 99775, USA 

1 . Introduction 

Most scientists would assume that information has been playing a role right from the 
beginning — the Big Bang. As the Universe evolved, after the gradual condensation of 
atoms and molecules and the formation of planetary systems, “islands” of increasing com- 
plexity and organization appeared, containing discrete aggregates of condensed matter with 
well-dehned boundaries and increasingly complex interactions with each other and their 
environment. Viewed this way, it indeed seems that the process of cosmic evolution itself 
is continuously generating information [Chaisson, 2001]. 

On second thought, however, aren’t we talking here of information /or us the observers 
or thinkers'! Did information as such really play an active role in the fundamental physical 
processes that shaped the Universe? Was information and information-processing involved 
at all in the evolution of the Universe before living organisms started roaming around and 
interacting with it, and intelligent beings began studying it? When and where did information 
begin to play an active role, actually controlling processes in the Universe? 

It is obvious that to address and answer these questions objectively we must first discuss 
in depth the concept of information and its meaning. We must find a dehnition of this 
ubiquitous and seemingly trivial concept that is truly objective and independent of human 
actions and human-generated devices, and which relates to its most fundamental property: 
that the mere presence of a pattern can trigger a macroscopic change in a system, and 
that this can happen repeatedly in a self-consistent manner. Traditional information theory 
does not help. It works mainly with communications and control systems and is not so 
much interested in an independent formal dehnition of information and its meaning as it 
is in a precise mathematical expression for the information content of a given message 
and its degradation during transmission, processing and storage. Shannon’s theory is not 
apt to express the information content in many non- technical human situations, nor is it 
adequate to measure information in biochemical systems. Consider the case of a genome: 
each one of the innumerable combinations of nucleotides has an equal a priori probability 
of appearance in random chemical synthesis, and all sequences of the same length have the 
same Shannon information content. Yet the corresponding molecules would have drastically 

* Abridged version of Roederer J. G., When and where did information first appear in the Universe? In 
Bioinformatics, J. Seckbach (ed.), Kluwer Acad. Publ., Dordrecht, The Netherlands, 2004. 


J. Seckbach et al. (eds.), Life in the Universe, 97-100. 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


different functional significance; only a minute fraction would be biologically meaningful. 
In other words, what counts is how information becomes operational. For this purpose, the 
concept of pragmatic information was introduced, linking the pattern in a “sender” with 
the pattern-specific change triggered in a “recipient” (Kiippers [1990]). It should be clear 
that information as a stand-alone concept has no absolute meaning: what counts is what 
information does, not what it is made of. 

1 shall try to accomplish the task of finding a comprehensive and objective definition 
of information by choosing the process of interaction as the underlying basic, primordial 
concept. I shall identify two fundamentally different classes of interactions between the 
bodies that make up the universe as we know it, with the concepts of information and 
information processing appearing as the key discriminators between the two. 

2. Physical and Biological Interactions 

It is our experience from daily life (and from precise observations in the laboratory) that 
the presence of one object may alter the state of other objects in some well-defined ways. 
We call this process an interaction — without attempting any formal definition (i.e., taking 
it as a “metaphysical primitive”). We just note that in an interaction a correspondence is 
established between certain properties of one object (its position, speed, form, etc.) and 
specific changes of the other. The interactions observed in the natural environment (i.e., 
leaving out all human-made artifacts) can be divided into two broad classes. 

The first class comprises the physical interactions between two bodies, in which we 
observe that the presence of one modifies the properties of the other (its motion, structure, 
temperature) in a definite way that depends on the relative configuration of both components 
of the system (their relative positions, velocities, etc.). Primary physical interactions between 
elementary particles are two-way (true inter-actions) and reversible. A most fundamental 
characteristic is the fact that during the interaction, there is a direct transfer of energy from 
one body to the other, or to and from the interaction mechanism itself. In other words, the 
changes that occur in the two interacting bodies are coupled energy-wise. I shall call the 
physical interactions between inanimate objects force-field driven interactions. 

For the second class of interactions, consider a dog walking around an obstacle. The 
dog responds to the visual perception of the obstacle, a complex process that involves 
information-processing and decision-making at the “receiver’s” end with a definite purpose. 
At the obstacle’s (the sender’s) side, we have scattering and/or reflection of incident light 
waves; no information and no purpose are involved — only physical processes are at work 
here. There is no energy coupling between sender and receiver; what counts is not the energy 
of the electromagnetic waves but the pattern of their spatial distribution (determined by the 
obstacle’s shape). 

We call this class of interactions information-based or information-driven [Roederer, 
2000]. Of course, the responsible mechanisms always consist of physical and/or chemical 
processes; the key aspect, however, is the control by information and information-processing 
operations. There is no direct energy coupling between the interacting bodies, although 
energy must be supplied locally for the intervening processes. In the first example the 
electromagnetic waves (light) themselves do not drive the interaction — it is the information 
in the patterns of the wave trains, not their energy, which plays the controlling role; the energy 


needed for change must be provided locally (by the organism). Quite generally, in all natural 
information-based interaction mechanisms the information is the trigger of physical and 
chemical processes, but has no relationship with the energy or energy flows needed by the 
latter to unfold. Physical and chemical processes provide a medium for information, but do 
not represent the information per se. The mechanisms responsible for this class of natural 
interactions must evolve', they do not arise spontaneously (in fact, Darwinian evolution itself 
embodies a gradual, species-specific information extraction from the environment). This is 
why natural information-driven interactions are all biological interactions. 

3. Information and Life 

Let us now formalize our description of information-based interactions, and point out both 
the analogies and differences with the case of physical interactions between inanimate bod- 
ies. First of all, we note that information-based interactions occur only between bodies or, 
rather, between systems the complexity of which exceeds a certain, as yet undefined degree. 
We say that system A is in information-based interaction with system B if the configuration 
of A, or, more precisely, the presence of a certain spatial or temporal pattern in system 
A (called the sender or source) causes a specific alteration in the structure or the dynam- 
ics of system B (the recipient), whose final state depends only on whether that particular 
pattern was present in A. The interaction mechanism responsible for the intervening dy- 
namic physical processes may be integral part of B, and/or a part of A, or separate from 
either. Furthermore: (a) both A and B must be decoupled energy-wise (meaning that the 
energy needed to effect the changes in system B must come from sources other than energy 
reservoirs or flows in A); (b) no lasting changes must occur as a result of this interaction 
in system A (which thus plays a catalytic role in the interaction process); and (c) the in- 
teraction process must be able to occur repeatedly in consistent manner (one-time events 
do not qualify). In other words, in an information-based interaction a specific one-to-one 
correspondence is established between a spatial or temporal feature or pattern in system 
A and a specific change triggered in system B; this correspondence depends only on the 
presence of the pattern in question, and will occur every time the sender and recipient are 
allowed to interact (in this basic discussion I will not deal with stochastic effects). 

We should emphasize that to keep man-made artifacts and technological systems (and 
also clones and artificially bred organisms) out of the picture, both A and B must be natural 
bodies or systems, i.e., not deliberately manufactured or planned by an intelligent being. 
We further note that primary information-based interactions are unidirectional (i.e., they 
are really “actions”, despite of which I shall continue to call them inferactions), going from 
the source or sender to the recipient. While in basic physical interactions there is an energy 
flow between the interacting bodies, in information-based interactions any energy involved 
must be provided (or absorbed) by reservoirs external to the interaction process. Energy 
distribution and flow play a defining role in complex systems [Chaisson, 2001]; however, for 
information-based interactions, while necessary, they are only subservient, not determinant, 
of the process per se. 

We must now provide a more formal definition: information is the agent that mediates the 
above described correspondence: it is what links the particular features of the pattern in the 
source system A with the specific changes caused in the structure of the recipient B. In other 


words, information represents and defines the uniqueness of this correspondence; as such, it 
is an irreducible entity. We say that “B has received information from A” in the interaction 
process. Note that in a natural system we cannot have “information alone”, detached from 
any interaction process past, present or future: information is always there /or a purpose — if 
there is no purpose, it isn’t information. Given a complex system, structural order alone 
does not represent information — information appears only when structural order leads to 
specific change elsewhere in a consistent and reproducible manner, without involving any 
direct transfer or interchange of energy. 

There are two and only two distinct types of natural (not made) information systems: 
biomolecular and neural. Bacteria, viruses, cells and the multicellular flora are governed by 
information-based interactions of the biomolecular type; the responses of individual cells 
to physical-chemical conditions of the environment are ultimately controlled by molecular 
machines and cellular organelles manufactured and operated according to blueprints that 
evolved during the long-term past. In plants they are integrated throughout the organism with 
a chemical communications network. For faster and more complex information processing in 
multicellular organisms with locomotion, and to enable memory storage of current events, 
a nervous system evolved which, together with sensory and motor systems, couples the 
organism to the outside world in real time. 

Since in the natural world only biological systems can entertain information-based 
interactions, we can turn the picture around and offer the following definition [Roederer, 
1978]: a biological system is a natural (not-human-made) system exhibiting interactions 
that are controlled by information. The proviso in parentheses is there to emphasize the 
exclusion of artifacts like computers and robots. By adopting the process of interaction as 
the primary algorithm, I am really going one step further and recognize information as the 
defining concept that separates life from any natural (i.e., not made) inanimate complex 
system. This answers the question asked in the title of this chapter: information appears in 
the Universe only wherever and whenever life appears. 

4. References 

Chaisson, E. J. (2001) Cosmic Evolution: the Rise of Complexity in Nature, Harvard University Press, Cambridge 

Kiippers B.-O. (1990) Information and the Origin of Life, The MIT Press, Cambridge Mass. 

Roederer, J. G. (2000) Information, life and brains, in: J. Chela-Flores, G. Lemarchand and J. Oro (eds.), Astro- 
biology, Kluwer Acad, Publ., Dordrecht, The Netherlands, pp. 179-194. 

IV. From the Miller Experiment to Chemical 
and Biological Evolution 



Facultad de Ciencias, UNAM Apdo. Postal 70-407 Cd. Universitaria, 
04510 Mexico, D.F., Mexico 

I. Introduction 

Laboratory experiments have shown how easy it is to produce a number of biochemi- 
cal monomers under reducing conditions. Such empirical support began to accumulate in 
1953, when Stanley L. Miller, then a graduate student working with Harold C. Urey at the 
University of Chicago, achieved the first successful synthesis of organic compounds under 
plausible primordial conditions The action of electric discharges acting for a week over 
a mixture of CH 4 , NH 3 , H 2 , and H 2 O; racemic mixtures of several proteinic amino acids 
were produced, as well as hydroxy acids, urea, and other organic molecules (Miller 1953). 
The easiness of formation in one-pot reactions of amino acids, purines, and pyrimidines 
strongly suggest these molecules and many others were components of the prebiotic broth 
(cf. Miller and Lazcano, 2002). 

However, the leap from biochemical monomers and small oligomers to living cells is 
enormous. There is a major gap between the current descriptions of the primitive soup 
and the appearance of non-enzymatic replication. Solving this issue is essential to our 
understanding of the origin of the biosphere: regardless of the chemical complexity of the 
prebiotic environment, life could not have evolved in the absence of a genetic replicating 
mechanism insuring the maintenance, stability, and diversification of its basic components. 

2. A Soup without Nucleic Acids? 

The organic monomers of abiotic origin described in the previous sections would have accu- 
mulated in the primitive environment, providing the raw material for subsequent reactions. 
As shown by numerous experiments, clays, metal cations, organic compounds bearing like 
highly reactive derivatives of HCN (such as cyanamide, dicyanamide, and cyanogen) or 
imidazole derivatives may have catalyzed polymerization reactions (Wills and Bada, 2000). 
Selective absorption of molecules onto mineral surfaces has been shown to lead to a suc- 
cessful surface-bound template polymerization up to 53 nucleotides (Ferris et al., 1996), 
and other processes like evaporation of tidal lagoons (Wills and Bada, 2000) and eutectic 


J. Seckbach et al. (eds.), Life in the Universe, 103 - 106 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


freezing of dilute aqueous solutions (Kanavarioti et al., 2001) could have also assisted 
concentration of precursors. 

Although the properties of RNA molecules make them an extremely attractive model 
for the origin of life, their existence in the prebiotic environment is unlikely. Thus, it is 
possible that the RNA world itself was the end product of ancient metabolic pathways 
that evolved in unknown pre-RNA worlds, in which informational macromolecules with 
different backbones may have been endowed with catalytic activity, i.e. with phenotype and 
genotype also residing in the same molecules, so that the synthesis of neither protein nor 
related catalysts is necessary (Orgel, 2003). 

The chemical nature of the first genetic polymers and the catalytic agents that may have 
formed the pre-RNA worlds are completely unknown and can only be surmised (Orgel, 
2003). Nonetheless, it is easy to imagine that as polymerized molecules became larger and 
more complex, some of then began to fold into configurations that could bind and interact 
with other molecules, expanding the list of primitive catalysts that could promote nonenzy- 
matic reactions. Some of these catalytic reactions, specially those involving hydrogen-bond 
formation, may have assisted in making polymerization more efficient. As the variety of 
polymeric combinations increased, some compounds may could have developed the ability 
to catalyze their own imperfect self-replication and that of related molecules. This could 
have marked the first molecular entities capable of multiplication, heredity, and variation, 
and thus the origin of both life and evolution (Bada and Lazcano, 2002). This scheme is 
necessarily speculative, but its intrinsic heuristic value cannot be underscored. Experiments 
with ribozymes appear to support the possibility that random mixtures of catalytic and 
replicative macromolecules were available in the primitive Earth, and provide an excel- 
lent laboratory model for understanding the evolutionary transition from the non-living to 

3. On the Early Evolution of Protein Biosynthesis 

Protein biosynthesis is a complex, exquisitely tuned process involving a large number of 
different components, which must have evolved in a step-wise fashion through a series of 
simpler stages. However, no such intermediate stages or simplified versions of ribosome 
mediated protein synthesis have been discovered among extant organisms. However, the 
fact that RNA molecules are capable of perfoming by themselves all the reactions involved 
in peptide-bond formation suggests that protein biosynthesis evolved in an RNA world 
(Zhang and Cech, 1998), i.e., that the first ribosome lacked proteins and was formed only 
by RNA. This possibility is strongly supported by the crystallographic data that has shown 
that ribosome catalytic site where peptide bond formation takes place is composed solely 
of RNA (Nissen et al., 2000). 

Clues to the genetic organization of primitive forms of translation are also provided 
by paralogous genes, which are sequences that diverge not through speciation but after a 
duplication event. Eor instance, the presence in all known cells of pairs of homologous genes 
encoding two elongation factors, which are GTP-dependent enzymes that assist in protein 
biosynthesis, provide evidence of the existence of a more primitive, less-regulated version 
of protein synthesis took place with only one elongation factor. The experimental evidence 
of in vitro translation systems with modified cationic concentrations lacking both elongation 


factors and other proteinic components (Spirin, 1986) strongly supports the possibility of 
an older ancestral protein synthesis apparatus prior to the emergence of elongation factors. 

4. Pushing Back the Molecular Fossil Record? 

How protein bisoynthesis actually evolved is still unknown. However, it is highly unlikely 
that the first proteins were complex enzymes with exquisitely, finely funed cafalyfic activity. 
Although the first peptides that were synthesized biologically (i.e., via ribosome-mediated 
translation) could have been selected by two properties that are not mutually exclusive, 
namely chaperone-like properties or catalytic activity, it can be assumed that a very sig- 
nificant characteristic would have been the possibility of stabilizing RNA-catalytic con- 
formations. This property would be the primitive equivalent to the stabilizing effect of the 
protein subunit of RNase P plays in vivo, and can be explored by a detailed analysis of 
extant RNA-binding sites. 

Structural analysis of conserved motifs of some polymerases also appear to provide in- 
sights into evolutionary stages older than DNA itself. All DNA polymerases whose tertiary 
structure has been determined share a common overall architectural feature comparable 
to a right hand shape. Detailed analysis of the three-dimensional structures of the pol I, 
pol II, and reverse transcriptase families have shown that their palm subdomain, which 
catalyzes the formation of the phosphodiester bond, is homologous in all of them, while 
the fingers and thumb subdomains are different in all four of the families for which struc- 
tures are known (Steitz, 1999). Homologous palm subdomains have also been identified in 
the viral T7 DNA- and RNA polymerases (Jeruzalmi and Steitz, 1998), indicating that it 
can catalyze the template-dependent polymerization of ribo- and of deoxyribonucleotides. 
As argued elsewhere (Delaye and Lazcano, 2000), the ample phylogenetic distribution of 
the catalytic palm subdomain and the flexible template- and substrate specificities of poly- 
merases suggests that the conserved palm subdomain described above is one of the oldest 
recognizable components of an ancestral cellular polymerase, that may have acted both as 
a replicase and a transcriptase during the RNA/protein world stage. 

5. Conclusions 

Although there have been considerable advances in the understanding of chemical processes 
that may have taken place before the emergence of the first living systems, life’s beginnings 
are still shrouded in mystery; how the transition from the non-living to the living took 
place is still unknown. However, analysis of RNA-binding motifs and conserved motifs of 
polymerases, among others, may provide insights into the RNA/protein world, providing 
insights into very early stages of biological evolution. 

Furthermore, the high levels of genetic redundancy detected in all sequenced genomes 
imply not only that duplication has played a major role in the accretion of the complex 
genomes found in extant cells, but also that prior to the early duplication events revealed 
by the large protein families, simpler living systems existed which lacked the large sets 
of enzymes and the sophisticated regulatory abilities of contemporary organisms. These 
redundancies support the idea that primitive biosynthetic pathways were mediated by small. 


inefficient enzymes of broad substrate specificity (Jensen, 1976). Larger substrate ranges 
may had not been a disadvantage, since relatively unspecific enzymes may have helped 
ancestral cells with reduced genomes overcome their limited coding abilities. 

6. Acknowledgments 

Support from UNAM-DGAPA Proyecto PAPIIT IN 111003-3 to A. L. is gratefully 

7. References 

Bada, J. L. and Lazcano, A. (2002) Some like it hot, but not the hrst biomolecules. Science 296 , 1982—1983. 

Becker, L., Blank, J., Brucato, J., Colangeli, L., Derenne, S., Despois, D., Dutrey, A., Ehrenfreund, R, Fraaije, H., 
Irvine, W., Lazcano, A., Owen, T., Robert, F. (2002) Astrophysical and astrochemical insights into the origin 
of life. Rep. Prog. Physics 65, R1-R56. 

Guerrier-Takada, C., Gardiner, K., Marsh, T., Pace, N., and Altman, S. (1983) The RNA moiety of ribonuclease 
P is the catalytic subunit of the enzyme. Cell 35 , 849—857. 

Jensen, R.A. (1976) Enzyme recruitment in the evolution of new function, Ann. Rev Microbiol. 30 , 409^25. 

Jeruzalmi, D. and Steitz, T. A. (1998) Structure of T7 RNA polymerase complexed to the transcriptional inhibitor 
T7 lysozyme. EMBO Jour. 17 , 4101^1 13. 

Kanavarioti, A., Monnard, P A., and Deamer, D. W. (2001) Eutectic phases in ices facilitate non-enzymatic nucleic 
acid synthesis. Astrobiology 1 , 481. 

Miller, S. L. (1953) A production of amino acids under possible primitive Earth conditions. Science 117 , 528. 

Miller, S. L. and Lazcano, A. (2002) Formation of the building blocks of life. In: J. W. Schopf (ed), Life’s Origin: 
The beginnings of biological evolution (California University Press, Berkeley), pp. 78-1 12. 

Nissen, P, Hansen, J., Ban., N., Moore, P. B. and Steitz, T. A. (2000) The structural basis of ribosome activity in 
peptide bond synthesis. Science 289 , 920-930. 

Orgel, L. E. (2003) Some consequences of the RNA world hypothesis. Origins Life Evol. Biosph. 33 , 21 1-218. 

Spirin, A. S. (1986) Ribosome structure and protein synthesis (Benjamin/Cummings, Menlo Park), 414 pp. 

Steitz, T. A. (1999) DNA polymerases: structural diversity and common mechanisms. J. Biol.Chem. 274 , 17395- 

Wachtershauser, G. (1988) Before enzymes and templates: theory of surface metabolism. Microbiological Reviews 
52 , 452^84. 

Wills, C. and Bada, J. (2000) The Spark of Life: Darwin and the primeval soup (Cambridge), 291 pp. 

Zhang, B. and Cech, T. R. (1998) Peptidyl-transferase ribozymes: trans reactions, structural characterization and 
ribosomal RNA-like features. Chem. Biol. 5 , 539-553. 




^Department of Biochemistry and Biophysics, Arrhenius Laboratories, 
Stockholm University, S-106 91 Stockholm, Sweden, ^ IFM Bioinformatics, 
Linkoping University, S-581 83 Linkoping and Centre for Genomics and 
Bioinformatics, Karolinska Institutet, S-1 71 77 Stockholm, Sweden, 
^Instituto de Bioqui'mica Vegetal y Fotosmtesis, CSIC-Universidad de 
Sevilla, Sevilla, Spain 

1. Introduction 

Conserved amino acid sequence motifs in enzymes often indicate involvement in the binding 
of metal ion(s) and/or in the binding and/or reactions of substrate(s). The four very early 
proteinaceous amino acids are glycine (G), alanine (A), aspartic acid (D) and valine (V) 
as was demonstrated with the clarification of the stepwise evolution of the genetic code 
(Eigen and Schuster, 1979), and in agreement with the quantities obtained in the earlier, 
classical work (Miller, 1953 and on) showing proteinaceous amino acid production under 
possible prebiotic conditions. Aspartic acid stands out as the unique very early amino acid 
containing an additional, highly reactive free charge, suitable i.a. for cation binding. Active 
site motifs with a very high content of any or all of these four amino acids may well be of 
early evolutionary significance. 

2. Very Early Sequence Motifs 

Some “early” proteins appear to harbor or reflect very early sequence motifs. For example, 
certain enzymes involved in inorganic pyrophosphate (PPi) metabolism, as well as in that of 
ATP, seem to be of particular significance in this connection. Special attention has recently 
been given to the integrally membrane-bound, proton-pumping PPi synthase, which in bac- 
terial photophosphorylation is the first and still only known alternative to the ubiquitous 
ATP synthase in biological electron transport coupled phosphorylation (Baltscheffsky et al . , 
1999). The putative active site of the PPi synthase from the purple photosynthetic bacterium 

* This paper is written in honor of Professor Stanley L. Miller. 


J. Seckbach et al. (eds.), Life in the Universe, 107-110. 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Rhodospirillum rubrum, in loop 5-6 (between transmembrane segments 5 and 6) has two 
nonapeptidyl sequences (DVGADLVGK and DNVGDNVGD), which are strongly con- 
served in the homologous enzyme family and which contain unusually many very early 
amino acids. Importantly, these sequences have charged amino acids regularly arranged in 
positions 1 , 5 and 9, five of these six being aspartic acid. We have discussed the possible 
roles of these charged amino acids in the putative active site for the binding and reactions 
of the inorganic phosphates (Baltscheffsky et al, 1999, 2001) and have described this with 
a preliminary sketch (Baltscheffsky etal, 2001). Notably, other loops may also be involved 
in the active site for these reactions (Schultz and Baltscheffsky, 2003). 

Recently, we counted the total number of occurrences of the sequence pattern D-A/GW- 
A/GW-A/GW-D-A/GW-A/GW-A/GW-D (as a possible predecessor of the nonapeptidyl 
sequence DVGADLVGK) in the Swissprot and TrEMBL databases (Boeckmann et al, 
2003) of October 2003. In total, we found 35 occurrences, which is four-fold more than 
could be expected by chance, indicating that this pattern is overrepresented, probably due 
to its functional or structural importance. We also checked the patterns 

D-G-A/GW-A/GW-D-G-A/GW-A/GW-D and 


These patterns showed to be even more overrepresented to the extent of 15 -fold and 27 -fold, 
respectively. The extremely strong overrepresentation of the G-D pattern appears to be in 
agreement with our preliminary observation that this pattern occurs particularly frequently 
in certain enzymes involved in energy transfer. We also compared the somewhat more 
general patterns D/E-(A/G/V)„-D/E-(A/GW)n-D/E, where n was set to 2, 3 or 4. For n —2, 
we arrived at the expected number of sequences, while for n = 3 and n = 4, the occurrences 
were between four- and seven-fold, also indicating some evolutionary selection caused by 
functional or structural requirements. 

A search for nonapeptidyl sequences in the Swissprot and TrEMBL databases, with D 
in positions 1, 5 and 9 and the other, very early A/GfV in the other positions, revealed that 
since 1996, several such sequences have been shown. DGGGDGGGD was an early found 
(Wen and Tseng, 1996) and dominating sequence, but also, from the year 2000 and on, 
have been reported. Several duplications at the tetrapeptide level and subsequent mutations 
would appear to have occurred. We interpret these findings as supporting our belief that 
the nonapeptide DVGADLVGK in PPi synthase may have evolved from DVGADLVGD or, 
earlier, DVGADVGAD. The introduction of K should have been useful in connection with 
the binding of anionic phosphate oxygen. 

Among the “very early” sequence motifs at active sites, that are found in some other 
PPi metabolizing enzymes, and also, more or less similar, in some ATP metabolizing 
enzymes, we shall discuss those found in phosphofructokinases, which show the motif 
GGDD in those operating with PPi and GGDG in those operating with ATP (Moore et al . , 
2002). In the '^"^GGDD^^^ sequence of the PPi-dependent phosphofructokinase from Bor- 
relia burgdorferi, '^"^GGD are three conserved active site residues and D'^^ is one of four 
residues suggested to be directly involved in PPi discrimination, by preventing ATP from 


3. Stepwise Motif Evolution 

The considerations presented above indicate our belief that strongly conserved sequence 
motifs with a high content of the four “very early” proteinaceous amino acids may be most 
useful for extrapolating molecular evolution backwards, possibly all the way from present- 
day structures to those operating soon after the origin of life. In connection with the early, 
stepwise evolution of the genetic code, we shall briefly consider two questions. 

The first concerns early polymers in molecular evolution. It has been suggested that 
high-molecular-weight polyphosphates may have preceded the nucleic acids and proteins 
(Komberg, 1995). It is tempting to speculate that, in connection with the early oper- 
ation of the first two triplets of the genetic code, the homopolymers polyglycine and 
polyalanine were produced. Could any of the three homopolymers discussed here, as 
intermediate stages between monomers and heteropolymers, have been useful in early 

The second question is based on the apparently uninterrupted function of the triplet 
genetic code from the time of its early start to the present day and age. On the basis of the 
information now available about DNA, RNA and proteins it might be useful to emphasize 
both the continuity and what may be called the constructivity based on the functioning of 
the triplet code in biological evolution of life on the Earth. 

4. A Principle of Constructive Continuity 

In connection with early discussions of the origin of the genetic code (Crick, 1968) and the 
evolution of the genetic apparatus (Orgel, 1968) a Principle of Continuity was used as a 
plausible guide. This principle required that each stage in evolution develops “continuously” 
from the previous one, and it was argued that certain features of the contemporary genetic 
system emerged very early (Orgel, 1968). 

All known life on Earth is based on DNA genomes, RNA, and protein enzymes. Today 
there are strong reasons to assume that these forms of life were preceded by a simpler 
life form, which in a so called “RNA world” was based primarily on RNA (Joyce, 2002). 
Whether a transition from such an RNA world first led to DNA genomes or to protein 
synthesis, the selection of proteinaceous amino acids in connection with the formation of 
the peptide bonds in protein synthesis may be assumed to have been steered by essen- 
tially the same triribonucleotide, or triplet, code which operates in the current forms of 

The triplets coding for the two first of the four very early proteinaceous amino acids 
were probably GGC for glycine and GCC for alanine (Eigen and Schuster, 1978), and a 
transition mutation in the mid-letters gave GAC, coding for aspartic acid, and GUC, coding 
for valine, respectively. The continuity from the two first used triplets over the very early 
stepwise evolution to the 4-, 8-, 16-, 32-, and to the 64-triplets to their present-day utilization 
in biological evolution has led to the remarkable “tree of life”, with which all known life 
is usually expressed (albeit with some slight variations). The increasing complexity clearly 
visible in over-all evolution and its constructivity may be briefly expressed in the following 
Principle of Constructive Continuity: 


The triribonucleotide (triplet) code has from its origin and early evolution provided 
genetic information to all life on the Earth. This continuity of information transfer at the 
triplet level over time has withstood various continuities and discontinuities at other levels, 
divergence and convergence, determinism and chance, in gene and genome evolution. The 
function of the triplet code has persisted through both major destructive (catastrophic) 
and constructive (anastrophic) changes, while the biological evolution, in discrete and 
“plausible” steps, has resulted in increasingly complex (“higher”) organisms, in a still 
ongoing constructive continuity at the fundamental level. 

We consider both the Principle of Constructive Continuity and the anastrophe concept 
(Baltscheffsky, 1997) to be realistic, rather than, for example, “optimistic” or “philosophi- 
cal”, and hope they will be useful in connection with investigations of various evolutionary 
matters. Will the proposed Principle be applicable for other parts of the cosmic evolutionary 
process, on the one side physical and chemical evolution and on the other side social, human 
and individual evolution? This is an open question. 

5. Acknowledgments 

Support from Carl Tryggers Stiftelse for Vetenskaplig Forskning, Magnus Bergvalls 
Stiftelse, Stiftelsen Wenner-Grenska Samfundet, Linkoping University and the Swedish 
Research Council is gratefully acknowledged. 

6. References 

Baltscheffsky, H. (1997) Major “anastrophes” in the origin and early evolution of biological energy conversion. 
J. theor. Biol. 187, 495-501. 

Baltscheffsky, M., Schultz, A. and Baltscheffsky, H. (1999) H+-PPases: a tightly membrane-bound family. FEBS 
Lett. 457 , 527-^533. 

Baltscheffsky, H., Schultz, A., Persson, B. and Baltscheffsky, M. (2001) Tetra- and nonapeptidyl motifs in the 
origin and evolution of photosynthetic bioenergy conversion. Possible implications for the molecular origin 
of phosphate metabolism. In: J. Chela-Flores, T. Owen and F. Raulin (eds.) First Steps in the Origin of Life in 
the Universe, Kluwer Academic Publishers, Dordrecht, pp. 173-178. 

Boeckmann, B., Bairoch, A., Apweiler, R., Blatter, M.C., Estreicher, A., Gasteiger, E., Martin, M.J., Michoud, K., 
O’Donovan, C., Phan, L, Pilbout, S. and Schneider, M. (2003) The SWISS-PROT protein knowledgebase and 
its supplement TrEMBL in 2003. Nucleic Acids Res. 31, 365-370. 

Crick, F.H.C. (1968) The origin of the genetic code. J. Mol. Biol. 38 , 367-379. 

Eigen, M. and Schuster, P. (1978) The hypercycle. Naturwiss. 65 , 341-369. 

Joyce, G.F. (2002) The antiquity of RNA-based evolution. Nature 418 , 214-221. 

Komberg, A. (1995) Inorganic polyphosphate: Toward making a forgotten polymer unforgettable. J. Bacteriol. 
177 , 491^96. 

Miller, S.L. (1953) A production of amino acids under possible primitive Earth conditions. Science 117 , 528-529. 

Moore, S.A., Ronimus, R.S., Robertson, R.S. and Morgan, H.W. (2002) The structure of a pyrophosphate- 
dependent phosphofructokinase from the lyme disease spirochete Borrelia burgdorferi. Structure 10 , 659-67 1 . 

Orgel, L.E. (1968) Evolution of the genetic apparatus. J. Mol. Biol. 38, 381-393. 

Schultz, A. and Baltscheffsky, M. (2003) Properties of mutated Rhodospirillum rubrum IT'' -pyrophosphatase 
expressed in Escherichia coli. Biochim. Biophys. Acta (in press). 

Wen, F.S. and Tseng, Y.H. (1996) Nucleotide sequence of the gene presumably encoding the adsorption protein 
of filamentous phage phi Lf. Gene 172 , 161-162. 



Department of Molecular Genetics and the Crown Human Genome Center, 
the Weizmann Institute of Science, Rehovot 76100, Israel 

I. Lipid World And The CARD Model 

A widespread notion is that life arose from a single molecular replicator, probably a self- 
copying polynucleotide, in an RNA World (Joyce, 2002). We have proposed an alterna- 
tive Lipid World scenario as an early evolutionary step in the emergence of cellular life 
on Earth (Segre et al, 2001). This concept combines the potential chemical activities of 
lipids and other amphiphiles, with their capacity to undergo spontaneous self-organization 
into supramolecular structures, such as micelles and bilayers. In quantitative, chemically- 
realistic computer simulations of our Graded Autocatalysis Replication Domain (GARD) 
model (Segre et al, 1998), we have shown that prebiotic molecular networks, potentially 
existing within assemblies of lipid-like molecules, manifest a behavior similar to self re- 
production or self-replication. 

Because amphiphile assemblies may form readily and spontaneously under prebiotic 
conditions (Deamer, 1985), the Lipid World scenario may represent an intermediate “meso- 
biotic” phase, bridging an a-biotic random collection of organic molecules with a biotic 
protocell that contains long biopolymers, as well as more intricate information storage, 
catalysis and replication (Shenhav et al, 2003). In our model, lipid-like amphiphiles may 
possess a very large variety of chemical structures, including head-groups that resemble 
amino-acids or nucleotides. Catalysis is proposed to be exerted by such diverse chemical 
moieties, enhancing amphiphile exchange rates as well the formation of more complex 
head-groups with similarity to peptides or oligonucleotides. In a more recent version of 
our model (Polymer GARD or P-GARD), a path is delineated for the gradually increased 
dependence on linear molecular sequences (Shenhav et al., in press). 

A most central notion in our P-GARD model is that life began with monomers only, 
and later proceeded to evolve biopolymers. This is in strict contrast to the widespread view, 
epitomized by the RNA World concept, whereby the abiotic formation of biopolymers 
is a prerequisite for life. In other words, RNA World or protein World proponents assert 
that a molecular entities devoid of biopolymers cannot possess the basic attributes of life. 
This credo derives from the premise that a living entity has to contain information and 
transmit it to progeny via replication, and that such a sequence of events cannot occur 


J. Seckbach et al. (eds.), Life in the Universe, 111 - 114 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


without long informational molecules that form similes hy base pairing, i.e. without nucleic 

The unorthodoxy of the Lipid World notion thus goes beyond the question of what 
chemical entities formed the hrst replicators - nucleotides, amino acids or lipids. In fact. 
Lipid World in its most general sense does not prescribe a particular chemistry, and only 
suggests that the hrst events en route to life were mediated by molecules capable of readily 
forming non-covalent aggregates. This allows a much wider diversity of compounds to take 
part in the hrst events leading to life, hence generates a more plausible scenario for life’s 
beginning in a highly heterogeneous primordial “soup”. 

In the basic model of monomer GARD, quasi-stationary assembly compositions (com- 
posomes) are shown to survive many splits, before giving rise to other quasi-stationary state 
or being scattered into “random drift” composition (Segre et al, 2000). Two major ideas 
underlie the GARD model. First is the notion of compositional information, namely that 
information can be stored in the distribution of compounds within the entity, rather by a 
sequence embodied within each compound. In other words, information is not a charac- 
teristic of an individual molecule, but of the system as a whole. Second is the capacity of 
that information to be transmitted along generations with acceptable hdelity. The transition 
between one composomal state and another can be viewed as an evolution-like process, in 
which one organism gives rise to another due to stochastic progression. 

2. Fitness Parameters and Populations of Assemblies 

Previously, we have mainly dealt with individual GARD assemblies, and at each split, one 
was randomly selected for further scrutiny. However, evolution is mostly about populations 
of organisms, displaying “ecological” relationships such as competition. We therefore have 
initiated a study of the properties of GARD assembly populations. Because of computing 
power limitations it is imperative to generate a phenomenological description of every 
composome in the realm of a higher level of analytical hierarchy. This is done by describing 
every composome with three kind of emergent property parameters (Shenhav etal . , in press). 
First is growth time, Ti, the time elapsing between assembly divisions, while the assembly is 
in a specihc composomal state i. Second is the survival perameter (Si), namely the probability 
of an assembly to preserve its composomal state following a split. Last is the emergence 
likelihood (Ei), which is the probability of entering a composomal state from another one 
or from random drift (a state in which the assembly possesses no composomal state). 
In a given population of assemblies and for specihc environment attributes, these htness 
parameters will provide a good approximation of the composomes population dynamics. 
In fact, it is possible to display this dynamics in a set of linear differential equations, using 
an “ecological” matrix that can be constructed using the three htness parameters. 

Our simulations showed that in most cases there is a dominant composome, in term of 
the Si and Ei, though other composomes might be much faster (small Ti) and therefore can 
be present in the population in a signihcant fraction (Eig. 1). Moreover, repeated simulations 
demonstrated that if the system is left to evolve without any constraint, the population distri- 
bution reaches a steady state, that could be interpreted as a stable “eco-system”. In any given 
set of parameters this state is unique, regardless of the initial population seeded. Imposing 
population constraints, such as constant population, prevents the system from converging 


Figure 1. Figure 1. Correlation between two of the fitness parameters. Dots represents slow composome 
(large Tj) and asterisks denote the top 20% fastest composomes (low Tj). Overall, there are 786 composomes, 
obtained from 100 Dimer-GARD simulations with different catalytic enhancement matrices, all drawn from 
the same catalytic values distribution (Segre et al, 2000). The survival parameter (Si) values behave roughly as 
a normal distribution, while the emergence likelihood (Ei) values obey an exponential-like distribution. There 
is a rough linear correlation between those two fitness parameters. It is interesting to note that the dominant 
composomes (having both large Si and Ei) tend to be slow, allowing the fast growing ones, located mostly in 
the middle bottom of the graph, to successfully compete, resulting with their significant representation in the 

on one state for long periods, though quasi-stationary population distribution can survive 
for substantial time before giving rise to an other. Interestingly, in the linear approximation 
of the “eco-system” dynamics that we have begun to pursue, the dominant population dis- 
tribution corresponds to the all-positive eigen-vector of the “ecological matrix”, in analogy 
to the dominant GARD composome being related to the all-positive eigen-vector of the 
catalytic-enhancements beta matrix (Segre et al., 2000). 

3. Towards Increasing Complexity — Synthesis of Polymers 

Our Monomer-GARD simulations (Segre et al, 2000) have a limited capability of creating 
metabolism-like systems with relatively high complexity, which is one of the basic features 
of evolution. In order to generate possible trajectories towards ever increasing complexity, 
we have introduced into our simulations a more elaborate form of metabolism, namely the 
capability of monomer to join each other to form oligomers. The basic interactions logic 
remains unchanged, and the only additional type of allowed interaction among molecules 
is the catalytic enhancement upon the oligomerization and bond-breaking rates. 


First we have used monovalent dimer and therefore restricted oligomerization to dimers 
only (Shenhav et ai, in press). Fig. 1 presents the distribution of the fitness parameters 
calculated for the 7 86 composomes obtained in one hundred such Dimer-GARD simulations 
with different catalytic enhancement matrices. 

Introducing divalent monomers, capable of generating polymer with unlimited length, 
highlights a central problem of such simulations, namely how to relate the dependence of the 
catalytic capacity of longer molecules to the catalytic capacity of the monomers composing 
it. At the one end are models in which the catalytic enhancement of a molecule is the sum 
of those of its monomers, and therefore the oligomerization contributes minimally to the 
overall catalysis in the system. An alternative scenario is that the catalytic characteristics of 
an oligomer are unrelated to those of its monomers, i.e. potencies are randomly assigned. 
The models of Dyson (Dyson, 1999) and Kaufmann (Kauffman, 1993) are good examples 
of these two options, respectively. At another extreme, oligomer-induced catalysis is non- 
linearly related to those of the constituent monomers, e.g. a product thereof, underlying 
synergism. Our preliminary results show that in a purely linear model, stable composomes 
do not form readily. The desirable model should compromise two opposing trends — the 
ability to sustain stable composomes while giving enough space for the evolution of more 
complex quasi-stationary states, in the course of time. 

Our main research objective is to define a basic set of interactions rules so that primitive 
genetic memory will become an emergent property, alongside with an increased complexity 
of the system. We anticipate that this could be achieved by a carefully designed set of 
oligomerization rules. It is not impossible that without synergism the system will not develop 
significance memory and complexity. Implementation of extended oligomer-based models 
could help bridge the gap between simple and close-ended systems to more elaborate ones 
that are essentially open-ended and therefore can serve as a true platform for the origin of 

4. References 

Deamer, D.W. (1985) Boundary Structures are Formed by Organic Components of the Murchison Carbonaceous 
Chondrite. Nature 317, 792-794. 

Dyson, F. (1999) Origins of life, Cambridge University Press, Cambridge. 

Joyce, G.F. (2002) The antiquity of RNA-based evolution. Nature 418 , 214-221. 

Kauffman, S. (1993) The origin of order, Oxford University Press. 

Segre, D., Lancet, D., Kedem, O., Pilpel, Y. (2001) Graded autocatalysis replication domain (GARD): Kinetic 
analysis of self-replication in mutually catalytic sets. Orig. Life Evo. Biosph. 28 , 501—514. 

Segre, D., Ben-Eli, D. and Lancet, D. (2000) Compositional genomes: Prebiotic information transfer in mutually 
catalytic noncovalent assemblies. Proc. Natl. Acad. Sci. USA 97, 41 12^1 17. 

Segre, D., Ben-Eli, D., Deamer D.W. and Lancet, D. (2001) The lipid world. Orig Life Evol. Biosph. 31 , 1 19-145 

Shenhav, B., Segre D. and Lancet D. (2003), Mesobiotic emergence: Molecular and ensemble complexity in early 
evolution. Adv. Complex Syst. 6, 15-35. 

Shenhav, B., Bar-Even, A., Kafri, R. and Lancet, D., Polymer GARD: simulation of covalent bond formation in 
reproducing molecular assemblies. Orig Life Evol. Biosph, in press. 


and Yu . L. ZEMSKOVA 

A. N. Bach Institute of Biochemistry, Russian Academy of Sciences, 
Leninsky Prospekt 33 (Bldg.2), Moscow, 119071, Russian Federation 

I. Introduction 

One of the main problems of the origin of life studies is chemical interpretation of the emer- 
gence of organisms capable of both keeping genetic information and catalyzing chemical 
reactions. The discovery of catalytically active RNAs, ribozymes, has permitted to assume, 
that early life was based on polyribonucleotides which could have served as their own 
genes and also performed catalytic functions in the absence of genetically ordered proteins 
(Gilbert, 1986). Ribozymes isolated from organisms and selected in vitro from random 
polynucleotides demonstrate an impressive repertoire of catalytic activities, which could 
give rise to the development of replication and translation mechanisms (Bartel and Unrau, 
1999). Some important reactions which protein enzymes do catalyze, in particular, redox 
processes that maintain energy metabolism in organisms, were not found in ribozymes. 
We believe that such catalytic inferiority of polynucleotides could be compensated by the 
attachment of coenzymes, the low molecular weight substances that combine in modern 
cells with apoproteins to form active enzymes. When energized by light, some coenzymes 
are efficient catalysts of electrons or chemical groups transfer in absence of apoproteins 
and thus could play a key role in RNA world metabolism (Kritsky et al., 1998; Kritsky and 
Telegina, 2004). 

2. Photochemical Activity of Coenzymes 

The free molecules of coenzymes are significantly less reactive than when combined into 
a complex with their apoprotein, but excitation by light strongly enhances their reactivity. 
In addition to UV-radiation with a wavelength maximum at 250 H- 280 nm absorbed by 
nucleic acid bases, flavins, pterins and reduced nicotinamides absorb UV-light of the area 
between 300 and 400 nm, and flavins are excited by visible light up to about 500 nm as well. 
Photoexcitation strongly enhances the reactivity of coenzymes. The absorption of photon 
by coenzyme heterocycle leads to the molecule transition to exited singlet states, which are 
efficiently converted into triplet states. From the standpoint of prebiotic chemistry, the latter 
are of more interest, because they can interact with other molecules in solution, whereas 
the excited singlet states are chemically quenched only in structurally ordered proteins. 


J. Seckbach et al. (eds.), Life in the Universe, 115 - 118 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


The midpoint redox potential value of flavins (E'o) is —0.22 V, i.e. reduced flavins are 
rather strong reductans. After transition to triplet state the E'o of the pertinent redox pair 
is shifted to +1.85 V because of energization of the oxidized form of the pair. Strongly 
electronophilic, it subtracts electrons from donors including those with highly positive E'o 
values. Pterins demonstrate similar properties; their lowest triplet state gets an additional 
energy of about 2.50 eV, whereas reduced forms, especially tetrahydropterins are strong 
reductants. The photochemical reactions of excited flavins and pterins involve a free radical 
mechanism and lead to a formation of metabolic reductants, dihydroflavins and dihydro- 
and tetrahydropterins, as well as to adduce the donor molecule’s radical (Heelis, 1982; 
Kritsky et al., 1997). The reduced nicotinamide coenzymes have been shown to sensitize 
the uphill electron transfer, too (Nikandrov et al., 1978). 

In the presence of inorganic electron acceptors such as dioxygen (O 2 ) and nitrate or 
organic molecules, for example, Fe^+ -cytochrome b, excited flavins and pterins catalyze 
donor-to-acceptor electron transfer. Although O 2 sharply decreases the viability of reduced 
coenzymes and changes the mechanism of photoreactions due to the generation of singlet 
oxygen (*© 2 ) and other reactive oxygen species, the reactions sensitized by excited flavins 
and pterins in oxygenic atmosphere lead to accumulation of free energy in products like they 
do in anaerobic conditions. Besides the reactions proceeding in aqueous solution, excited 
lipophilic flavin embedded in a lipid membrane was shown to sensitize translocation of 
redox equivalents across this membrane. Moreover, considering a strong difference of proton 
dissociation constants of the ground state and excited molecule, the excitation and relaxation 
cycle of flavins was predicted to act in light-dependent transmembrane translocation of 
proton (Schmidt, 1984). 

3. The Attachment of Coenzymes to Polynucleotides 

By using modern methods of in vitro randomization, selection and amplification of polynu- 
cleotides a number of RNA aptamer complexes, a type of synthetic oligonucleotides that 
non-covalently bind a particular target molecule, were synthesized and selected for their 
affinity to riboflavin, flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), 
nicotinamide mononucleotide (NMN), nicotinamide dinucleotide (NAD) and reduced forms 
of latter two molecules (Lauhon and Szostak, 1995; Fan et al., 1996; Roychowdhury-Saha 
et al., 2002). The nucleic acid strands with covalently attached coenzymes can arise from 
chemical and enzymatic reactions. For example, synthetic pteridine analogs of purine bases 
were incorporated into non-terminal positions of nucleic covalent linkage by automated 
DNA synthesis (Hawkins, 2001). In other experiments coenzymes were covalently attached 
at the ends of RNA molecules in reactions catalyzed by protein and RNA catalysts. NAD and 
FAD substituted adenosine triphosphate in the initiation of the template-dependent RNA 
synthesis catalyzed by Escherichia coli RNA-polymerase (Malygin and Shemyakin, 1979). 
A shortened version of a Tetrahymena thermophila ribozyme was shown to catalyze the 
self-incorporation of NAD (Breaker and Joyce, 1995). Catalytic RNA was shown to create 
5', 5'-pyrophosphate linkages with FMN and nicotinamide adenine dinucleotide phosphate 
(NADP) (Huang and Yarns, 1997). Terminal transferase from calf thymus accepted nicoti- 
namide nucleoside 5'-triphosphate and efficiently added the NMN residue to the 3'-end of 
the oligodeoxyribonucleotide, and the T4 polynucleotide kinase accepted NMN as substrate. 


The same study showed that reduced NADP was an excellent substrate for polynucleotide 
phosphorylase of Micrococcus luteus in polymerization and in primer extension reactions 
(Liu and Orgel, 2000). 

At first glance coenzyme heterocycles show a worse spatial conformity to RNA structure 
than the common bases. However, the ketone groups of flavins and amido group of nicoti- 
namide have been reported to participate in hydrogen base pairing with nucleic acid bases 
(Liu and Orgel, 2000; Fan et al., 1996). Due to a closeness of pteridine structure to purine, 
the presence of this uncommon base was minimally disruptive for DNA double-stranded 
structure (Hawkins et al, 2001). 

4. On the Role of Photoreactive Coenzymes in Evolution 

The simulation of processes on primitive Earth has shown that catalytically significant 
heterocycles of coenzymes were available from chemical evolution (Oro, 2001). Although 
the ability of RNA-attached coenzymes to drive primitive metabolism at the expense of 
captured energy of solar radiation can be regarded as a positive selection character, which 
favored the further development of the system, its negative consequence was an increased 
risk of photodegradation of the bases situated in vicinity of the coenzyme’s heterocycle. It is 
noteworthy to recall that flavins and pterins, but not nucleic bases are active generators 
(Neverov et al., 1996). 

After having been rejected from polynucleotide carriers because of their relative struc- 
tural unfitness as compared to canonic nucleotides, coenzymes have managed to survive in 
evolution by changing their host polymer. The development of genetically ordered polypep- 
tides had to lead to the appearance of amino acid sequences displaying affinity to coenzymes. 
In its turn, this affinity could have become a strongly favorable characteristic encouraging 
the survival of those organisms, whose genotypes were capable to encode such polypeptides, 
since their presence provided a wider set of catalytic activities. Flavins and pterins have re- 
tained, however, their role of photochemically active redox reagents. In modern metabolism, 
besides their function in enzyme catalysis, these coenzymes act as photosensors govern- 
ing the activity of some enzymes and protein transcription factors (De la Rosa et al., 1989; 
Christie and Briggs, 2001; Iseki et al., 2002; Cheng et al., 2003). Considering the struc- 
tural diversity of photochemically active coenzyme-binding proteins, it is reasonable to 
believe, that they have not arisen from a common ancestor, but are products of convergent 

5. Summary 

According to the RNA world hypothesis, RNAs in primitive organisms have served as their 
own genes and also performed catalytic functions in metabolism. However, some catalytic 
activities necessary for development of metabolism, e.g. oxidoreductases, were not found 
in ribozymes. It is suggested that catalytic inferiority of RNA world could be compen- 
sated by the activity of coenzyme molecules attached to polynucleotides and displaying 
photocatalytic functions. 


6. Acknowledgement 

Support from Russian Foundation for Basic Research Grant 0 1 -04-48268a is acknowledged. 

7. References 

Bartel, D.P. and Unrau, PJ. (1999) Constructing an RNA world, Trends Biochem. Sci., 241, 9-13. 

Breaker, R.R. and Joyce, G.F. (1995) Self-replication of coenzymes by ribozymes, J. Mol. EvoL, 42, 551-558. 

Cheng, P, He, Q., Yang., Y, Wang, L., and Liu, Y. (2003) Functional conservation of light, oxygen, or voltage 
domains in light sensing, Proc. Natl. Acad. Sci. USA, 100, 5938-5943. 

Christie, J.M. and Briggs, W.R. (2001) Blue light sensing in higher plants, J. Biol. Chem, 276, 1 1457-1 1460. 

De la Rosa, M.A., Roncel, M., and Navarro, J.A. (1989) Flavin-mediated photoregulation of nitrate reductase. 
A key point of control in inorganic nitrogen photosynthetic metabolism, Bioelectrochem. Bioenerg., 27, 

Fan, R, Suri, A.K., Fiala, R., Live, D., and Patel, J.D. (1996) Flavin recognition by an aptamer targeted toward 
FAD, J. Mol. Biol., 258, 480-500. 

Gilbert, W. (1986) The RNA World, Nature, 319, 618. 

Hawkins, M.E. (2001) Fluorescent pteridine analogs — a window on DNA interaction. Cell. Biochem. Biophys., 
34, 257-281. 

Iseki, M., Matsunaga, S., Murakami, A., Ohno, K., Shiga, K., Yoshida, K., Sugai, M., Takahashi, T., Hori, T., and 
Watanabe, M. (2002) A blue-light-activated adenylyl cyclase mediates photoavoidance of Euglena gracilis. 
Nature, 415, 1047-1051. 

Kritsky, M.S., Lyudnikova, T.A., Mironov, E.A., and Moskaleva, I.V. (1997) The UV radiation-driven reduction 
of pterins in aqueous solution, J. Photochem. Photobiol., B: Biol., 48, 43^8. 

Kritsky, M.S., Kolesnikov, M.P., Lyudnikova, T,A., Telegina, T.A., Otroshchenko, V,A., and Malygin, A.G. (2001) 
The nucleotide- and nucleotide-like coenzymes in primitive metabolism, photobiology and evolution. In: J. 
Chela-Flores, T. Owen., andF. Raulin (eds.). First Steps in the Origin of Life in the Universe. Kluwer Academic 
Publishers, Dordrecht, pp 237-240. 

Kritsky, M.S. and Telegina, T.A. (2004) Role of nucleotide-like coenzymes in primitive evolution. In: J. Seckbach 
(ed.) Origins: Genesis, Evolution and Diversity of Life, Kluwer Academic Publishers, Dordrecht, pp 000-000 
(in press). 

Lauhon, C.T. and Szostak, J.W. (1995) RNA aptamers that bind flavin and nicotinamide redox cofactors, J. Am. 
Chem. Soc., 117, 1246-1257. 

Liu, R. and Orgel, L.E. (2000) Enzymatic synthesis of polymers containing nicotinamide mononucleotide, Nucl. 
Acid. Res., 23, 3742-3749. 

Malygin, A.G. and Shemyakin, M.F. (1979) Adenosine, NAD and FAD can initiate template dependent RNA 
synthesis catalyzed by Escherichia coli RNA polymerase, FEBS Letts., 102, 51-54. 

Neverov, K.V., Mironov, E.A., Lyudnikova, T.A., Krasnovsky, A. A., Jr., and Kritsky, M.S. (1996) Phosphorescence 
analysis of the triplet states of pterins in connection with their photoreceptor functions in biological systems. 
Biochemistry (Moscow), 61, 1149-1155. 

Nikandrov, V.V., Brin, G.P., and Krasnovskii, A.A. (1978) Light-induced activation of NADH and NADPH, 
Biochemistry (Moscow) 43, 636-645. 

Roychowdhury-Saha, M., Lato, S.M., Shank, E.D., and Burke, D.H. (2002) Flavin recognition by an aptamer 
targeted toward FAD, Biochemistry, 41, 2492-2499. 

Oro, J. (2001) Cometary molecules and life’s origin. In: J. Chela-Flores, T. Owen., and F. Raulin (eds.). First Steps 
in the Origin of Life in the Universe. Kluwer Academic Publishers, Dordrecht, pp 1 13-120. 

Schmidt, W. (1984) The study of basic photochemical and photophysical properties of membrane-bound flavins: 
The indispensable prerequisite for the elucidation of primary physiological blue light action. In: H. Senger 
(ed.). Blue Light Effects in Biological Systems, Springer Verlag, Berlin, etc., pp. 81-94. 



^ Bahn Biotechnology Co., RR2 Box 239A, Mt. Vernon, IL 62864 USA, 
^Department of Plant Biology, Southern Illinois University, Carbondale, 
IL 62901 USA. ^ 250^/2 Charles St., Carbondale, IL 62901 USA 

We show here that a hot origin of life (Fox & Dose, 1977) is more consistent with exper- 
imental and observational evidence than is a cold origin of life (Bada & Lazcano, 2002; 
Miller & Lazcano, 1995). 

In his classic 1953 origin-of-life experiment Stanley Miller (1953) generated amino 
acids by circulating a mixture of CH 4 , NH 3 , H 2 , and H 2 O vapor past an electric discharge 
with a temperature of hundreds to thousands of degrees C for a week. Lightning discharges 
have temperatures in the tens of thousands of degrees C (Uman, 2001). Miller’s system 
also utilized a reservoir of boiling water at 100°C. It would be interesting to repeat Miller’s 
experiment but with a very hot wire as the energy source instead of an electric discharge. We 
predict that this variation of his experiment would produce a similar array of amino acids. 
Harada & Fox (1964) did in fact subject CH 4 , NH 3 , and H 2 O to passage through a glass 
tube heated to 1000°C and obtained a product amino acid distribution similar to Miller’s 
famous experiment. That heat is important in the prebiotic synthesis of amino acids (Fox, 
1995) was shown by Fox & Windsor (1970) who produced amino acids by heating NH 3 and 
H 2 CO with a hot iron pipe at a temperature of 950° C. Oro (1960) synthesized the purine 
adenine by heating NH 4 CN at 90°C for 24 hours. Fox & Harada (1961) synthesized the 
pyrimidine uracil by heating malic acid and urea in the presence of poly phosphoric acid 
at 140°C for 2 hours. Heat thus appears to have had an important role in the formation of 
prebiotic monomers. 

On the hot Primitive Earth, the first biopolymers to be formed were probably made by 
the thermal dehydration condensation of prebiotic monomers into protobiopolmers. This 
result seems inevitable wherever there are heat sources of any sort and monomers. The 
heat sources could be thermal convection, meteoritic impact, lightning discharge, infrared 
radiation, shock wave, or others. For example. Fox & Harada (1958) prepared thermal 
proteins, or proteinoids, by heating mixtures of amino acids above 100°C for a few hours. 
Rohlfing (1976) prepared thermal proteins by heating mixtures of amino acids at 65°C for 
a few weeks. The thermal polymerization of sugars into polysaccharides has long been 
known as the process of caramelization. Fox & Bahn (1990) heated glucose and fructose in 
the presence of glutamic acid at 140°C for 12 hours to form polyglucofructose. Schwartz 
(1962) heated ribose at 150°C for 12 hours to form polyribose. Some progress has been 
made in the thermal polymerization of mononucleotides into oligonucleotides. Schwartz, 
Bradley, & Fox (1965) heated CMP with polyphosphoric acid at 85°C for 6 hours to make 


J. Seckbach et al. (eds.), Life in the Universe, 119 - 120 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


oligo-C. Matsuno and his colleagues (Ogasawara et al., 2000) heated mononucleotides 
under simulated hydrothermal vent conditions at 1 10°C for 1 hour to get oligonucleotides. 
With respect to lipids, Hargreaves, Mulvihill, & Deamer (1977) made phospholipids by 
heating fatty acids, glycerol, and phosphate at 65° C for one week. Thermal polymerization 
of prebiotic monomers into protobiopolymers is decidedly nonrandom (Bahn & Pappelis, 
2001), with the various sequences that are formed being highly influenced by side-by- 
side interactions of the various monomers involved. The first informational contents to 
be encoded in the first biopolymers on the Primitive Earth may have been for sequences 
that were most heat-stable out of all the possible sequences that could have occurred. The 
very first “genes” may have been for heat-stability. The first RNA sequences in the RNA 
World may have been protogenes for maximal heat-stability. This possibility is supported 
by all the available evidence that the Last Common Ancestor of all life on Earth was a 
hyperthermophile Archean. 

In conclusion, heat appears to have been a universal catalyst and powerful environmental 
shaper in the transformation of inorganic matter into living matter. 


Bada, J.L. & Lazcano, A. (2002) Some Like it Hot, But Not the First Biomolecules, Science 296 , 1982-1983. 

Bahn, P.R. & Pappelis, A., in Chela-Flores, J., Owen, T., & Raulin, F. (eds.), (2001) HPLC Evidence of Nonran- 
domness in Thermal Proteins, First Steps in the Origin of Life in the Universe, Kluwer Academic Publishers, 
Boston, pp 69-72. 

Fox, S.W. (1995) Thermal Synthesis of Amino Acids and the Origin of Life, Geochim. Cosmochim. Acta 59 

Fox, S.W. & Bahn, P.R. (1990) Process for Preparing Thermal Carbohydrates, U.S. Patent Number 4,975,534. 

Fox, S.W. & Dose, K. (1977) Molec. Evol. & the Orig. of Life, Marcel Dekker Inc., New York. 

Fox, S.W. & Harada, K. (1958) Thermal Copolymerization of Amino Acids to a Product Resembling Protein, 
Science 128 , 1214. 

Fox, S.W. & Harada, K. (1961) Synthesis of Uracil Under Conditions of a Thermal Model of Prebiological 
Chemistry, Science 133 , 1923-1924. 

Fox, S.W. & Windsor, C.R. (1970) Synthesis of Amino Acids by the Heating of Formaldehyde and Ammonia, 
Science 170 , 984-986. 

Harada, K. & Fox, S .W. ( 1 964) Thermal Synthesis of Natural Amino Acids from a Postulated Primitive Terrestrial 
Atmosphere, Nature 201, 335-336. 

Hargreaves, W.R., Mulvihill, S.J., & Deamer, D.W. (1977) Synthesis of Phospholipids and Membranes in Prebiotic 
Conditions, Nature 266, 78-80. 

Miller, S.L. (1953) A Production of Amino Acids Under Possible Primitive Earth Conditions, Science 117 , 528- 

Miller, S.L. & Lazcano, A. (1995) The Origin of Life - Did it Occur at High Temperatures?, J. Mol Evol 41 , 

Ogasawara, H., Yoshida, A., Imai, E., Honda, H., Hatori, K., & Matsuno, K. (2000) Synthesizing Oligomers from 
Monomeric nucleotides in Simulated Hydrothermal Environments, Orig. Life & Evol Biosphere 30 , 5 19-526. 

Oro, J. (1960) Synthesis of Adenine from Ammonium Cyanide, Bioch.Biophy.Res.Com 2, 407^12. 

Rohlfing, D.L. (1976) Thermal Polyamino Acids: Synthesis at Less than 100°C, Science 193 , 68-70. 

Schwartz, A.W. (1962) The Thermal Polymerization ofRibose, M.S. Thesis, Florida State Univ. 

Schwartz, A.W., Bradley, E., & Fox, S.W., in Fox, S.W. (ed.), (1965) Thermal Condensation of Cytidylic Acid in 
the Presence of Polyphosphoric Acid, The Origins of Prebiological Systems & of Their Molecular Matrices, 
Academic Press, New York, pp 317-326. 

Uman, M.A. (2001) The Lightning Discharge, Dover Publications, Inc., Mineola, NY. 



^Institute of Biomolecular Chemistry, CNR, Department of Organic 
Chemistry, University of Padova, 35131 Padova, Italy ^DSM Research, 
Life Sciences, Advanced Synthesis and Catalysis, P.O. Box 18, 6160 MD 
Geleen, The Netherlands 

I. Introduction 

A growing evidence has recently been accumulated on the presence of chiral, C“- 
tetrasubstituted a-amino acids with a significant L (S) enantiomeric excess (up to 15%) 
in carbonaceous chondritic meteorites. The amino acids analysed to date, extracted from 
several samples of the Murchison and Murray meteorites, include isovaline (Iva), C“-methyl 
norvaline [(aMe)Nva], C“-methyl valine [(aMe)Val], C“-methyl isoleucine [(aMe)Ile], and 
C“-methyl a/Zoisoleucine [(aMe)alle] (Cronin and Pizzarello, 1997; Pizzarello and Cronin, 
2000; Pizzarello et al., 2003). 

These amino acids are either extremely rare (Iva) or totally unknown (all of the others) 
in the terrestrial biosphere. Therefore, the reported enantiomeric excesses can be hardly as- 
cribed to a terrestrial contamination of the samples. Moreover, C“-tetrasubstitution protects 
amino acids against racemization. 

These results have suggested that C“-tetrasubstituted a-amino acids of extraterrestrial 
origin could have been the seeds for homochirality of life in our planet (Bada, 1997). 
However, this hypothesis implies that the enantiomeric excesses would have been somehow 
transferred from C“-tetrasubstituted a-amino acids to protein amino acids. 

Herewith we describe the results of a study aimed at determining if C-activated deriva- 
tives or peptides based on chiral, C“-tetrasubstituted a-amino acids could have reacted with 
protein amino acids and favoured the incorporation of one of their enantiomers over the other. 

2. Results and Discussion 

We have investigated the stereochemical outcome of reactions involving N-acetylated, 
homo-chiral (L) homo-oligomers (from dimer through octamer) of C“-tetrasubstituted 
a-amino acids [Iva, (aMe)Nva, (aMe)Leu and (aMe)Val] activated at the C-terminus 
as 5(4i/)-oxazolones, and a large excess of the racemate of a proteinogenic amino acid 


J. Seckbach et al. (eds.), Life in the Universe, 121 - 122 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


methyl ester (e.g., H-D,L-Val-OMe). The choice of the 5(4i/)-oxazolone as the activated 
intermediate is rooted on the fact that oxazolones are formed to a signihcant extent from 
C“-tetrasuhstituted a-amino acid residues hy nearly all activation methods used for peptide 
synthesis. In particular, oxazolones are generated very easily by intramolecular dehydration 
of C“-tetrasubstituted peptides with a free C-terminus (Formaggio et al., 2003). 

Our results indicate that homo-peptide oxazolones based on chiral, C“-tetrasubstituted 
ot-amino acids are indeed able to exert chiral discrimination when reacting with the race- 
mate of a protein amino acid. The diastereomeric excesses of the peptides formed in the 
various reactions range from 3 to 64%. However, the direction of the stereoselection is 
bimodal, in that peptide oxazolones with shorter main-chain length and less bulky side 
chains preferentially incorporate the proteinogenic amino acid of the same chirality as that 
of the C“-tetrasubstituted residues, whereas longer main chains (which promote the onset 
of (3-turns and 3io-helices at the tetramer and pentamer levels, respectively) and bulky side 
chains in the peptide oxazolone direct the selection towards the proteinogenic amino acid 
of the opposite chirality. These hndings can be explained on the basis of the reaction mech- 
anism, in which the transition state is reactant-like (Crisma et al., 1997), of the participation 
to the stereoselection by both the C-terminal and the penultimate residues of the peptide 
oxazolone (with opposite effects), and of the turn/helix handedness and stability. 

Our results suggest that two extreme scenarios can be envisaged, depending on the 
relative abundance of C“-tetrasubstituted ct-amino acids of different bulkiness and on the 
extent to which relatively long peptide chains, containing mostly residues of this kind, may 
have formed on the early Earth. Either (i) short C“-tetrasubstituted peptides, with simple side 
chains, by seeding the preferential incorporation of L proteinogenic amino acids of the same 
chirality, may have promoted the growth of longer and progressively more chirally uniform 
peptides through amplification processes, or (ii) longer C“-tetrasubstituted peptides, with 
bulky side chains, may have depleted the racemic primordial soup of proteinogeic amino 
acids of their D isomers, thus generating an L excess from which the homochirality of life 
could have been developed. 

3. References 

Bada, J.L. (1997) Meteoritics — Extraterrestrial handedness?. Science 275 , pp. 942*943. 

Crisma, M., Valle, G., Formaggio, R, Toniolo, C. and Bagno, A. (1997) Reactive intermediates in peptide synthesis: 
first crystal structures and ab initio calculations of 2-alkoxy-5(4//)-oxazolones from urethane-protected amino 
acids, J. Am. Chem. Soc. 119 , pp. 4136—4142. 

Cronin, J.R. and Pizzarello, S. (1997) Enantiomeric excesses in meteoritic amino acids, Science 275 , pp. 951-955. 

Formaggio, F, Broxterman, Q.B. and Toniolo, C. (2003) Synthesis of peptides based on C“-tetrasubstituted 
a-amino acids, in Houben-Weyl Methods of Organic Chemistry, Vol. E22c, Synthesis of Peptides and Pep- 
tidomimetics. Goodman, M., Felix, A., Moroder, L. and Toniolo, C. (eds.), Stuttgart: Thieme, pp. 292-310. 

Pizzarello, S. and Cronin, J.R., (2000) Non-racemic amino acids in the Murray and Murchison meteorites, Geochim. 
Cosmochim. Acta 64 , pp. 329-338. 

Pizzarello, S., Zolensky, M. and Turk, K.A. (2003) Nonracemic isovaline in the Murchison meteorite: chiral 
distribution and mineral association, Geochim. Cosmochim. Acta 67, pp. 1589-1595. 



^Direccion General de Divulgacidn de la Ciencia, UNAM. Cd. 
Universitaria, A.P. 70-487, Mexico, 04510 D.F., Mexico, and ^Instituto de 
Ciencias Nucleares, UNAM, A.P. 70-453, D.F. 04510, Mexico 

Abstract. We develop a simple model using a Markov chain approach for the oligomeriza- 
tion of amino acids, based on electromagnetic differences among reacting amino acids. Such 
model can explain an experimental oligomerization process that shows a remarkable bias in 
its products. Such results may be of importance as it makes more accessible the replication of 
minimal chemical machinery compatible with life processes. 

I. Introduction 

The polymerization phenomena associated to the origin of life had to be a strongly biased 
process. Otherwise, the probability of nucleation of a ‘minimum living chemical system’ 
would be excluded (Mosqueira, 1988). We resort to the self-ordering principle (Fox and 
Dose, 1977) that establishes that the reactivity between different reacting amino acids is 
not even. Thus, we grouped them into four different sets (Dickerson and Geis, 1969). 

We apply this model to the products formed in a dry heating mixture of the amino 
acids glycine, tyrosine and glutamic acid (Nakashima et ak, 1977). Nakashima and collab- 
orators reported only those trimers containing tyrosine and found only two trimers from 
36 theoretically possible tripeptides, assuming complete randomness. Further, this reaction 
mechanism has been investigated by Hartmann et al. (1981). With such knowledge, our 
model is able to account for the production of the two trimers observed (Mosqueira et ak, 

2. Markov Chain Formalism Applied to the Thermal Polymerization 
of Amino Adds 

We consider only nearest pair-wise interactions among reacting species. The main assump- 
tion is that the transition probability associated to the chemical incorporation of new specie 
is influenced only by the interaction between the incoming specie and the reactive end of 
the oligomers. It is not influenced by any other previous monomer already bonded in the 
n-oligomer. We use a Markov chain formalism to model the dry heating reaction of the 


J. Seckbach et al. (eds.), Life in the Universe, 123 - 124 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


specified amino acids. Let us define a finite Markov chain (Moran, 1984): 

Prob(XT+i = m|Xo = a, Xj = b, . . . , Xjk) = Prob(XT+i = mjXj = k), (1) 

where a, b, . . . ,m are arbitrary designations of the states assumed by system X at time 0, 
1, . . . , T, T+1, . . . Under such construction, it is possible to follow the state of the system as 
the oligomerization proceeds. For this we use the following equation: P(n)=AP(n_i), Where 
P(n) and P(n-i) are the vectors of the n and n— 1 states respectively, and A is the transition or 
reactivity matrix with elements aij. These are obtained from the four groups classification of 
amino acids (Dickerson and Geis, 1969): polar positive (p+), polar negative (p— ), neutral 
(n), and non polar (np). So, we arrange the four possible electromagnetic interactions 
between amino acids into a 4 x 4 matrix as follows: 
















The state of the system at any stage “k” is represented by row matrix with four elements: 
(p+ p- n np). 

3. Remarks 

To the present stage, we have applied this model to reacting mixtures containing only 
two groups of amino acids at a time. We have found that despite of the numerical values 
assigned to its elements, only three different situations arise that are discussed elsewhere 
(Mosqueira et ak, 2002). Further, we applied our model through the three stages of the 
reaction mechanism (Hartmann et al. 1981), (i.e., initiation, elongation and termination) and 
successfully explain the production of only two trimers reported by Nakashima et al. (1977). 

4. References 

Dickerson, R.E. and Geis, I. (1969) The Structure and Action of Proteins, Harper & Row Publishers, New York. 
Fox, S. and Dose, K. (1977) Molecular evolution and the origin of life, Marcel Dekker, Inc., New York. 
Hartmann, J., Brand, M.C., and Dose, K (1981) Formation of specific amino acid sequences during thermal 
polymerization of amino acids, BioSystems 13, 141-147. 

Moran, P.A.P. (1984) An Introduction to Probability Theory, Clarendon Press, Oxford. 

Mosqueira, F.G. (1988) On the Origin of Life Event, Origins of Life and Evolution of Biosphere 18, 143-156. 
Mosqueira, F.G., Ramos-Bernal, S., Negron-Mendoza, A. (2000) A simple model of the thermal prebiotic oligomer- 
ization of amino acids, BioSystems 57, 67-73. 

Mosqueira, F.G., Ramos-Bemal, S., Negron-Mendoza, A. (2002) Biased polymers in the origin of life, BioSystems 



and M. S. KRITSKY* 

^A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, 
Moscow; ^The Russian Federation State Research Center “Troitsk Institute 
for Innovation and Fusion Research” , Troitsk, Moscow Region; 

^A.N. Frumkin Institute of Electrochemistry, Russian Academy of Sciences, 
Moscow, Russian Federation. 

Earlier models for organic synthesis in the conditions of sulfide hydrotherms were based on 
the ability of sulfide minerals (chalcogenides) and hydrogen sulfide to act as electron donors 
in chemical reduction of water-dissolved CO 2 to organic molecules (for literature sources see 
Vladimirov etai, 2004). The detailed analysis suggests a possibility of another mechanism: 
a direct electrochemical reduction of CO 2 at the surface of metal-sulfide minerals, for 
instance pyrite or galenite. When putting forward this hypothesis, we proceeded from the 
fact that electrode potentials of sulfide minerals can reach considerable magnitudes varying 
with composition and structure of mineral. Because chalcogenides are capable of conducting 
electrical current, the contact of mineral bodies of different structures must lead to arising 
of galvanic circuits with an electromotive force of about several volts. The functioning of 
such circuits has been registered under natural conditions. 

The combination in sulfide minerals of semiconductor properties with a relatively low 
adsorption activity and the presence of traces of transient metals makes them a good cathode 
material. Our experiments demonstrated the increase of cathode current on rotating pyrite 
electrode in a range of potentials more negative than -800 mV in presence of CO 2 and 
revealed the dependence of this current from the CO 2 diffusion rate, temperature and ionic 
composition of aqueous phase. In these experiments, however, no formation of organic 
substances was observed. 

According to mechanism of the CO 2 reduction established in the studies of cathode 
materials other than pyrite, the electron tunneling from cathode to a CO 2 molecule produces 
an active particle, the radical-ion COj . Further transformation of this ion-radical can lead to 
formation of carboxylic acids such as formate or a less reduced product, carbon monoxide. 
The rate of CO 2 reduction to organic molecules increases under high pressure, when aqueous 
media acquire a number of properties of non-aqueous solvents. Since the hydrotherms in 
earth crust exist under the pressure reaching hundreds of Bars, the further experiments were 
performed in the device we have designed to test the possibility of electrosynthesis of organic 


J. Seckbach et al. (eds.), Life in the Universe, 125 - 126 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


substance under high pressure. The device included an electrolyzer placed in an autoclave. 
The design of the autoclave enabled us to perform studies at pressures up to 3000 Bar and 
simultaneously permitted continuous passage of CO 2 through the cathode compartment of 
the electrolyzer. The housing of the electrolyzer was made from fluoroplastic and presented 
two separated electrode compartments of 130 cm^ working volume each. The cathode was a 
monolith disc, 5 mm thick and 30 mm in diameter, cut out from a pyrite crystal. The catholyte 
and anolyte compartments were separated with an MK-40 cation exchange membrane. The 
counter electrode was a Pt plate of 30 mm in diameter and 0.2 mm thick and the reference 
electrode was a saturated AgCl electrode. In the course of 24 hour experiment, CO 2 was 
bubbled through the catholyte (0. IM KHCO 3 ). The pressure of CO 2 in the autoclave and in 
the electrolyzer was being maintained at a rate of 50 Bar at room temperature. The control of 
process and all measurements were made at a distance, outside the protective system of the 
device. The potential in the electrochemical cell was provided by means of a potentiostat and 
a programmer connected with a voltmeter and a register device (for details of experiment 
see Vladimirov et al, in press). On completion of the experiment, the content of organic 
products of CO 2 reduction was determined by a color reaction with chromotropic acid. 

As the potential of cathode was increased up to -800 mV, substantial amounts of formate 
were revealed in the catholite. The current (Faradaic) efficiency of its accumulation grew 
up to -1000 mV where it was 0.12%. The yield of formate increased exponentially with 
potential. In none of the experiments formation of free formaldehyde was registered. The 
following experiments were performed as controls. (1) The reactor filled with O.IM KHCO 3 
solution was bubbled by CO 2 (50 Bar, 10 ml min~') during 24 hours without potential 
imposed on pyrite cathode. (2) The — 1 Volt potential was imposed for 24 hours on the 
pyrite cathode placed in O.IM KHCO 3 solution without CO 2 bubbling and under normal 
atmospheric pressure. (3) The —1 Volt potential was imposed for 24 hours on the pyrite 
cathode placed in O.IM KHCO 3 solution and the reactor was bubbled by N 2 (50 Bar, 10 
ml min“') during 24 hours. In none of these control experiments formation of formate or 
other organic products was registered. 

Thus, the reduction of CO 2 on a pyrite cathode in aqueous solutions pH = 7 at potentials 
higher than -800 mV and a pressure of 50 Bar resulted in the formation of a simplest organic 
acid. Our data suggest that in neutral and weekly acidic solutions accompanying deep-lying 
deposits of sulfide ore (more fhan 500 m below crust surface) as well as in the regions 
of “black smokers” at the ocean floor there may occur formation of organic substances by 
direct electrochemical reduction of CO 2 in the cathode regions of mineral galvanic systems. 

Support from Russian Foundation for Basic Research Grant 01-04-48268 is appreciated. 


Vladimirov, M.G., Ryzhkov, Y.F., Alekseev V.A., Bogdanovskaya, V.A., Otroshchenko,V.A., and Kritsky, M.S. 
(2004) Electrochemical reduction of carbon dioxide on pyrite as a pathway for abiogenic formation of organic 
molecules. Origins of Life and Evolution of the Biosphere (in press). 

Last Common Ancestor may have Arisen from Genome Fusion 


Strada Sottopiazzo, 18, 14056 Boglietto (AT), ITALY 

1. Introduction 

The origin of the genetic code and early evolution of life on earth has fascinated researchers 
for many decades. The recent availability of complete genome sequences provides a molec- 
ular ‘fossil record’ which can be accessed by reconstructing amino acid sequences corre- 
sponding to ancient gene duplications. 

The present study was stimulated by the idea that as evolution proceeds in small steps, 
individual amino acids should have been added to the genetic code, one at a time. Sampling 
conserved sequences may identify that subset of amino acids used at the time of gene 
duplication. Collection of many such samples can elucidate the chronological order in which 
amino acids were first coded into proteins. In this study we examine families common to 
most living organisms - so called Clusters of Othologous Groups of proteins (COGs) - 
those present in modem Bacteria, Eukarya, and Archaea. 

2. Materials and Methods 

Clustal 1.81 software was used to align over 3238 families of proteins downloaded from . Of these, 934 families were discarded because they con- 
tained less than 8 modem sequences. A partial sequence reconstruction was attempted on 
the remainder by the (rather crude) method of accepting an amino acid as being conserved 
if it is in the majority at a site in the alignment. A simple count of all such conserved amino 
acids is made for each family. Of these, a further 2158 families were discarded by accepting 
only those ancestral counts containing a significant number of amino acids - a high residue 
limit of 100 was used leaving just 146 partially reconstructed sequences. 

3. Results 

We expect all 20 amino-acids to be represented in about 89% of the sequences reconstmcted, 
reflecting the assumption that the modem genetic code of 20 amino acids was inherited 
from LCA. Instead we find that in 32 cases both tryptophan and cysteine are missing, in 
38 cases cysteine is missing but tryptophan is present, in 30 cases cysteine is present but not 
tryptophan. Only in 37 (25%) cases out of the total of 146 are all 20 amino acids present. 


J. Seckbach et al. (eds.), Life in the Universe, 127 - 128 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


4. Discussion 

The absence of either tryptophan or cysteine is incompatible with the conjecture that amino 
acids were added one at a time to an earlier sub-set. Nor can systematic bias in the elaboration 
of the data could be responsible. For example if there were a bias towards aligning cysteine 
residues then we have a difficulty explaining why such residues are absent in the tryptophan 
rich ancestral sequences and vice versa. 

One possibility may be that a speciation event occurred when neither tryptophan nor 
cysteine were part of the genetic code. In one species cysteine, and in the other tryptophan 
independently appropriated UGN codon(s) and the two organisms continued to evolve 
developing new proteins with distinct, possibly incompatible genetic codes. Unlike most 
other amino acids which share the same family box, cysteine and tryptophan have different 
properties, consistent with this hypothesis. Later genome fusion took place between these 
two species and diverging rapidly towards Bacteria, Eukarya, and Archaea. Perhaps the new 
fused genome provided significant advantages, sufficient to lead to the eventual extinction 
of all other forms of life. 

Preliminary indications suggest that the two parents of the fusion specialized in some- 
what different biochemistries. The typtophan encoding ancestor developed enzymes in- 
volved in membrane transport and ATPase. The cysteine encoding ancestor developed 
NAD/FAD and DNA repair enzymes. 

The approach and conclusions of this study differ from those of Trifonov who has 
used amino acid frequencies to estimate chronology. Modern amino acid frequencies quite 
accurately reflect base composition and the codon assignments of the genetic code. The 
amino acid absence criterion used here, less dependent of any conjecture regarding either 
base composition or codon assignments is likely to be more reliable. Given the ubiquity 
of horizontal gene transfer, Trifonov’s use of only 2 enzymes per family to reconstruct 
conserved motifs may also be inadequate. 

5. Summary 

A method to estimate the relative chronological order of the amino acids and ancient gene 
duplication events before the LCA is illustrated. The last two amino acids added to the 
genetic code, were tryptophan and cysteine but these two probably originated in distinct 
species whose genomes fused. Full details of the 146 alignments can be requested from the 
author ( 

6. References 

Higgins, D.G., Bleasby, AJ. and Fuchs, R. (1992) CLUSTAL V: improved software for multiple sequence 
alignment. Computer Applications in the Biosciences (CABIOS), 8(2):189-191. 

Tatusov etal. (2000). The COG database: a tool for genome-scale analysis of protein functions and evolution. 
Nucleic Acids Res. 28: 33-6. 

Trifonov, E.N. (2000) Glycine clock: Eubacteria first, archaea next, protoctista, fungi, plants and animalia at last. 
Gene Therapy & Mol. Biol., 4: 313—323. 

Collis W J M F (2000) Evolution of Protein Synthesis. Origins of Life and Evolution of the Biosphere, 30: 337. 


Department of Animal Biology and Genetics, Via Romana 17-19, 
1-50125 Florence, Italy 

1. Introduction 

Contemporary genomes are the result of 3.5-4 billions of years of evolution. Their history 
can be traced using the increasing number of available sequences and a panel of bioinfor- 
matic tools. As a result it is now possible to shed some light on the mechanisms involved 
in their evolution and responsible for the shaping of metabolic pathways. These analyses 
also enabled to shed some light on the mechanisms and forces that drove the evolution 
of the earliest genes and genomes. Whole-genome comparison demonstrates that a high 
proportion of the gene set of different prokaryotes results from ancient gene duplications. 
Thus, the duplication of DNA sequences appears to have played a very important role in the 
evolution of genes and genomes. It suggests that the earliest living organisms contained a 
small number of genes that gave rise to new genes by duplication followed by evolutionary 
divergence. In the 30s Haldane and Muller suggested that duplicated genes might acquire 
different mutations eventually arriving to code for products with different catalytic features. 

Sequences evolved from a common ancestor are referred to as homologs. These, in turn, 
are called orthologs, if they originated after a speciation event or paralogs if they emerged 
after a gene duplication event. Serial duplications of homologous genes can give rise to 
a group of paralogous genes, a paralogous gene family. Duplication may involve DNA 
stretches whose length is variable, resulting in the duplication of fragments containing part 
of a gene, one or more genes, and complete genomes too. 


The so-called Oparin-Haldane hypothesis, proposed in the 20s, postulated that abiotically 
produced organic compounds accumulated on the Earth surface, and that life emerged in a 
nutrient-rich environment (the primordial soup). This view received an experimental support 
in 1953, when S.L. Miller, using a sterile apparatus simulating the pre-biotic environment 
where life originated, obtained aminoacids and other biogenic compounds (Miller, 1953). 
According to this hypothesis, the first living entities were heterotrophic. However, the 
progressive exhaustion of the prebiotic supply of nutrients resulted in a selective pressure 
that enabled the survival only of those microorganisms that have become able to produce 
autonomously those nutrients whose concentration was decreasing in the environment. 
Thus, the building up of new metabolic pathways represented a crucial event in molecular 


J. Seckbach et al. (eds.), Life in the Universe, 129 - 132 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


and cellular evolution, since the ancestral organisms became progressively less- dependent 
on the organic compounds prebiotically synthesized. 

Several hypotheses on the origin and evolution of metabolic pathways have been pro- 
posed, but the most attractive one is the so-called patchwork hypothesis (Jensen, 1976), 
according to which metabolic pathways may have been assembled through the recruitment 
of primitive enzymes that could react with a wide range of chemically related substrates. 
Such relatively slow, non-specific enzymes may have enabled primitive cells containing 
small genomes to overcome their limited coding capabilities. 

2. Results 


Nitrogen fixation is widespread in bacteria and archaea. In the free-living diazotroph 
Klebsiella pneumoniae the nif genes are clustered in a single chromosomal region and 
are organized into several operons. The enzyme responsible for nitrogen fixation is called 
nitrogenase. All known Mo-nitrogenase consist of two components: the dinitrogenase, a 
012^2 tetramer encoded by nifD and nifK genes, and the dinitrogenase reductase, a homod- 
imer coded for by the nifH gene. Nitrogenase contains two metal clusters, one of which is 
the iron-molybdenum cofactor (FeMo-co), the site of dinitrogen reduction and whose syn- 
thesis requires the activity of an another tetrameric enzymatic complex (Nif N 2 E 2 ) whose 
subunits are encoded by nifE and nifN. 

The detailed analysis of the nifDK and nifEN pairs of genes showed that their products 
share common features (Fani et al., 2000): they code for tetrameric complexes, and the 
products of nifE and nifN are structurally related to the nifD and nifK products, respectively. 
Finally, those diazotrophs in which nifDK and/or nifEN have been characterized share the 
same gene organisation. The four genes are clustered in operons where the two genes of 
each pair are contiguous and arranged in the same order {nifDK and nifEN). Moreover, the 
four genes shared a high degree of sequence similarity suggesting that they belong to a 
paralogous gene family. Fani et al (2000) proposed a two-steps evolutionary model leading 
to these genes. The model proposes the existence of a single ancestral gene that underwent 
an in-tandem gene duplication event, which gave rise to a bicistronic operon. Then, this 
ancestral operon duplicated leading to the ancestors of the present-day nifDK and nifEN 

If the ability to fix nitrogen was a primordial property, then the duplication events leading 
to the two operons predated the appearance of the last common ancestor of Archaea and 
Bacteria. Thus the function(s) performed by the primordial enzyme would have evolved 
because of the composition of the atmosphere. Theories vary from strongly reducing to 
neutral; but it is generally accepted that O 2 was absent, an essential prerequisite for the 
evolution of an ancestral nitrogenase, as free oxygen inactivates it. The first living organisms 
were probably heterotrophic anaerobes and dependent on abiotically produced organic 
matter for their metabolism. Depending on the composition of the early atmosphere (neutral 
or reducing), the ancestor gene coded for an enzyme with a nitrogenase or a detoxyase 
activity, respectively. The first duplication event, leading to the ancestral bicistronic operon, 
followed by divergence, refined the specificity of the primitive nitrogenase/detoxyase, which 


might have also been involved in the biosynthesis of a Fe-Mo cofactor. Successively the 
ancestral operon duplicated and the following divergence lead to the appearance of the 
ancestors of the present day nifDK and nifEN operons which encoded different proteins 
involved in reducing substrates and biosynthesize FeMo cofactor, respectively. Thus, the 
ability to fix nitrogen appears to be an ancient property and might have arisen during an early 
period of cellular evolution. The corresponding genetic information could have been lost 
in many strains, possibly in the course of adaptation to changing environmental conditions 
and the associated selective pressures upon microorganisms. Nevertheless, the high degree 
of conservation of nitrogenase genes within archaeal and bacterial diazotrophs suggests that 
lateral transfer of nif genes might have occurred frequently. 


Histidine biosynthesis is one of the best-characterized anabolic pathways. There is a large 
body of genetic and biochemical information, including operon structure, gene expression, 
and an increasingly larger number of sequences available for this route. This pathway has 
been extensively studied, mainly in Escherichia coli and Salmonella typhimurium. In all 
histidine-synthesizing organisms the pathway is unbranched and consists of nine intermedi- 
ates, all of which have been described, and of eight distinct proteins that are encoded by eight 
genes, hisGDCBHAF(IE) that, in E. coli, are arranged in a compact operon. As previously 
reported, there are several independent indications of the antiquity of this pathway suggest- 
ing that the entire route was assembled long before the appearance of the Last Universal 
Common Ancestor (LUCA) of the three extant cell domains. Histidine biosynthesis plays 
an important role in cellular metabolism, since it is interconnected to both the de novo syn- 
thesis of purines and to nitrogen metabolism. How the his pathway originated remains an 
open question, but the detailed analysis of the structure and organization of the his genes in 
(micro)organisms belonging to different phylogenetic archaeal, bacterial and eucaryal lin- 
eages revealed that at least three molecular mechanisms played an important role in shaping 
the pathway, that is gene elongation, paralogous gene duplication(s), and gene fusion (Pani 
et al., 1994, Brilli and Fani, 2003). Moreover, genetic and sequence data show that once the 
entire pathway was assembled it underwent major rearrangements during evolution. A wide 
variety of different clustering strategies of his genes have been documented suggesting that 
many possible histidine gene arrays exist. According to the patchwork hypothesis on the 
origin and evolution of metabolic pathways, several histidine biosynthetic genes appears 
to have been assembled by recruitment of preexisting broad-specificity enzymes following 
gene duplications. Two of these genes, hisA and hisF, are particularly interesting from an 
evolutionary point of view. Their products catalyze sequential reactions in histidine biosyn- 
thesis, they are paralogous and share a similar internal structures (Fani et al. 1994). The 
detailed comparative analysis of the HisA and HisF proteins revealed that they might be 
subdivided into two paralogous modules half-the size of the entire genes. This finding led 
to the suggestion that the two genes are the outcome of two ancient paralogous duplication 
events. According to the model proposed, the first duplication involved an ancestral mod- 
ule (half the size of the present-day hisA gene) and led by a gene elongation event to the 
ancestral hisA gene, which in turn underwent a duplication, that gave rise to the hisE gene. 
Since the overall structure of the hisA and hisF genes are the same in all known (micro) 


organisms, it is likely that they were part of the genome of the last common ancestor and that 
the two dnplication events occurred long before the separation of Archaea from Bacteria. 
The biological significance of the hisA-hisF structure relies on the structure of the encoded 
enzymes. The two proteins have a TIM-barrel structnre, so the ancestral gene probably 
coded for a half-barrel enzyme. The elongation event leading to the ancestor of hisAlhisF 
genes enabled the covalent fusion of two half-barrel coding seqnences, permitting the pro- 
duction of a complete barrel whose activity was then rehned by natural selection acting on 
mutated alleles. The same happened for the whole-barrel gene after its duplication, resulting 
in modern-day HisA and HisF. The reminiscence of this last duplication event may lie in 
the physical closeness between the two genes in present-day genomes. 

3. Summary 

In the course of evolution different molecular mechanisms acted amplifying the coding and 
metabolic abilities of organisms. It is clear that the DNA duplication is a major force in that 
sense. The evidence for gene elongation, gene duplication and operon duplication events 
suggests in fact that the ancestral forms of life might have expanded their coding abilities 
and their genomes by “simply” duplicating a small number of mini-genes via a cascade of 
duplication events, involving DNA sequences of different size. 

4. References 

Alifano, P. Fani, R. Lio, P. Lazcano, A. Bazzicalupo, M. Carlomagno, MS. Bruni, CB. (1996) Histidine biosynthetic 
pathway and genes: structure, regulation, and evolution. Microbiological Review 60, 44-69. 

Brilli, M. and Fani, R. (2003) Molecular evolution of hisB genes. Journal of Molecular Evolution (in press). 

Fani, R. Gallo, R. and Lio, P. (2000) Molecular evolution of nitrogen fixation: the evolutionary history of nifD, 
nifK, nifE, and nifN genes. Journal of Molecular Evolution 5 1 , 1-1 1 . 

Fani, R. Lio, P. Chiarelli, I. and Bazzicalupo, M. (1994) The evolution of the histidine biosynthetic genes in 
prokaryotes: a common ancestor for the hisA and hisF genes. Journal of Molecular Evolution 38, 489-95. 

Jensen, R.A. (1976) Enzyme recruitment in evolution of new function. Annual Review of Microbiology 30, 409-25. 

Miller, S.L. (1953) A production of amino acids under possible primitive earth conditions. Science 1 17, 528-9. 

An Evolutionary Perspective 


^ Professor(Biophysics), Department of physics, University of Pune, Pune, 
India-41 1007. ^Research Fellow (Biophysics), Department of Physics, 
University of Pune, Pune, lndia-41 1007. ^Lecturer, Bioinformatics Center, 
University of Pune, Pune, India-411007. 

I. Introduction 

The evolution of intelligent behavior observed in metazoan species requires a steady 
and sufficient supply of energy. Photosynthesis assumes the important role in the evo- 
lutionary mechanism in this respect. Since the basic mechanism of photosynthesis has 
remained unchanged in the evolutionary pathway, the study of the molecular evolution 
of the photosynthetic proteins has gained importance. Ribulose-l,5-bisphosphate carboxy- 
lase/oxygenase (RuBisCO) catalyses the first step in the CO 2 assimilation in Photosyn- 
thesis. RuBisCO exists as dimmer in case of prokaryotic autotrophs as revealed by the 
crystallographic structure in case of bacteria Rhodospirilium rubrum (Schinder et al 1986). 
It exists as a multimeric protein in case of the higher vascular plants viz Spinach (Chap- 
man et al 1988) and Tobacco (Chapman MS et al 1987). In the present study amino acid 
sequence analysis of the RuBisCO large chains have been carried out using bioinformatics 

2. Material and Methods 

RuBisCO large chain complete sequences representative of different categories of plants 
have been retrieved from the databases. Multiple Sequences Alignment (MSA) was done 
using the CLUSTALW package. Phylogenetic tree has been constructed by using the 
treeing algorithm of the PHYLIP package (Felsenstein, 1985) from the profile output of the 
CLUSTALW. Pairwise alignment of the sequences has been carried out using the PASTA 
(version 3.0) program (Pearson, 1988) and the percentage amino acid identities have been 
determined. For the detailed analysis of the conserved regions the secondary structure 
prediction has been carried out using the web version of the Predict Protein package (Rost, 


J. Seckbach et al. (eds.), Life in the Universe, 133 - 134 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


3. Results 

The MSA obtained from the CLUSTALW program reveals the occurrence of the conserved 
amino acid stretches i.e. oligopeptides, in all the species investigated in the study (Table 1)*. 
The PASTA Pairwise comparison of the sequences shows that the amino acid identity varies 
from 85%-96% among higher plants, 52-88% among algae and 37-82% among bacteria 
(Table 2). This indicated that the higher plants sequences are highly homologous while the 
bacterial sequences are the least. The Phylogenetic tree shows the clustering of the sequences 
broadly into three groups: A (archaeal sequences), B (bacterial and Algal sequences) and C 
(higher vascular plants) (Fig 1). Mismatch among the homologous regions are suggestive of 
the occurrence of point mutations in the evolutionary pathway. The pentapeptide “SGGIPI” 
is conserved except in Archea. Other point mutations of relevance is the emergence of the 
mostly hydrophilic peptide “SDDGH” in higher plants from the hydrophobic counter parts 
“LGVDQ” in Archea and “IGVDQ” in bacteria (Table 3). 

4. Conclusions 

The analysis done here shows that the RuBisCO large chains are most diverse among the 
lower autotrophs viz. Archea, followed by the Bacteria and are highly conserved in case 
of the higher plants. However the efficiency of this enzyme has remained low along the 
evolutionary pathway. This low efficiency, as it is known, puts burden on the plants for 
producing the enzyme in large quantities. Since food production is the priority in case of 
autotrophs, energy is diverted for maintenance of the production-related machinery. This 
may be the reason that being autotrophs the plants did not develop intelligent behavior 
as animals. So, in the search of life elsewhere this point needs to be considered. One has 
to search for both autotrophs and heterotrophs if Darwinian evolution is assumed to be a 
universal phenomenon. 

5. References 

Chapman, S. and Won, S. (1987) Sliding layer conformational change limited by the quaternary structure of plant 
RuBisCO. Nature 329, 354-356. 

Chapman, S. and Won, S. (1988) Tertiary structure of Rubisco: Domains and their contacts. Science 241, 71-74. 
Schinder, G. and Lindquist, Y. (1986) Three-dimensional structure of ribulose-1, 5-bisphosphate carboxylase/ 
oxygenase from Rhodospirillum rubrum at 2.9 A resolution. EMBO J. 5 no. 13, 3409-3415. 

Rost, B. (1993) Prediction of protein structure at better than 70% accuracy. J Mol. Biol 232, 584—599. 
Felsenstein, J. (1998) Phylogeny interference package. Cladistics 5, 164-166. 

Pearson, W. and Lipman, D. (1988) Improved tools for biological sequence analysis. PNAS 85, 2444-2448. 
Pearson, W. R. (1998). Empirical statistical estimates for sequence similarity searches. Int. J. Mol. Biol. 276, 

[For all Tables and Figures please visit]. 



^Department of Biochemistry, Biophysics and Macromolecular Chemistry, 
University of Trieste, Via Giorgieri, 1, 1-34127, Trieste, Italy, ^Permanent 
Institute: Department of Biochemistry, Federal University of Technology, 
Akure, Nigeria, ^The Abdus Salam ICTP, 1-34014, Trieste, Italy and 
Institute de Estudios Avanzados, Caracas, Venezuela. 

Abstract. Convergent evolution is an ubiquitous phenomenon, since it occurs at the levels of 
morphology, physiology, behavior (Eisthen and Nishikawa, 2002), and at the molecular level 
(Pace, 2001). Evolutionary convergence is significant for the central problem of astrobiology. 
Since all forms of life known to us are terrestrial, it is relevant to question whether the science 
of biology is of universal validity (Dawkins, 1983), and whether the molecular events that were 
precursors of the origin of life are bound to occur elsewhere in the universe wherever conditions 
are similar to the terrestrial ones. We discuss evolutionary convergence and its classification 
into functional, mechanistic, structural and sequence convergence (Doolittle, 1994), which 
should help us in the context of astrobiology defining bioindicators in the exploration of the 
solar system. 

1. Introduction 

The question “What would be conserved if the tape of evolution were played twice?” which 
is relevant to astrobiology has been raised repeatedly in the past (Fontana and Buss, 1994); 
it underlies one of the basic questions in astrobiology. Since all forms of life known to us 
are terrestrial organisms, it is relevant to the question of whether the science of biology is 
of universal validity (Dawkins, 1983; Chela-Flores, 2003). 

The sharp distinction between chance (contingency) and necessity (natural selection 
as the main driving force in evolution) is relevant for astrobiology. Independent of his- 
torical contingency, natural selection is powerful enough for organisms living in similar 
environments to be shaped to similar ends. Our examples will favor the assumption that, 
to a certain extent and in certain conditions, natural selection may be stronger than chance 
(Conway-Morris, 1998; 2002). We raise the question of the possible universality of bio- 
chemistry, one of the sciences supporting chemical evolution. 

2. Evolutionary Divergence and Convergence 

The universal nature of biochemistry has been discussed from the point of view of the basic 
building blocks (Pace, 2001). One of the main points made in that paper is that it seems 


J. Seckbach et al. (eds.), Life in the Universe, 135 - 138 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


likely that the building blocks of life anywhere will be similar to our own. Amino acids 
are formed readily from simple organic compounds and occur in extraterrestrial bodies 
such as meteorites. Themes that are suggested to be common to life elsewhere in the 
cosmos are the capture of adequate energy from physical and chemical processes to conduct 
the chemical transformations that are necessary for life: lithotropy, photosynthesis and 
chemosynthesis. Other factors in favor of the universality of biochemistry are physical 
constraints (temperature, pressure and volume), as well as genetic constraints. 

Divergence and convergence are two evolutionary processes by which organisms be- 
come adapted to their environments. Evolutionary convergence has been dehned as the ac- 
quisition of morphologically similar traits between distinctly unrelated organisms (Austin, 
1998). While there are many examples of molecular divergence, the same is not true of 
molecular convergence. Convergent evolution is said to occur when a particular trait evolves 
independently in two or more lineages from different ancestors. This is distinct from par- 
allelism, which refers to independent evolution of a trait from the same ancestor. Although 
many of the best-known examples of convergence are morphological, convergence occurs 
at every level of biological organization. However, this paper focuses on molecular conver- 
gent evolution. We would like to proceed with examples of molecular convergence along 
the classification by Doolittle (1994) into Functional, Mechanistic, Structural and Sequence 


This refers to molecules that serve the same function but have no sequence or structural 
similarity and carry out their function by entirely different mechanisms. Despite the fact 
that alcohol dehydrogenases in vertebrates and Drosophila bear no sequence similarity, and 
their tertiary structures are entirely different, they catalyze alcohol into acetaldehyde by 
different chemical reactions; they both remove hydrogen from alcohol (Doolittle, 1994). 


Mechanistic convergence occurs when the sequence and structure of molecules are very 
different but the mechanisms by which they act are similar. Serine proteases have evolved 
independently in bacteria (e.g. subtilisin) and vertebrates (e.g. trypsin). Despite their very 
different sequences and three-dimensional structures, they are such that the same set of 
three amino acids forms the active site. The catalytic triads are His 57, Asp 102, and Ser 
195 (trypsin) and Asp 32, His 64 and Ser 221 (subtilisin), thus giving a consensus catalytic 
triads of the sort [Asp/Glu] His [Ser/Thr] (Doolittle, 1994, Tramontano, 2002). 


This refers to molecules with very different amino acid sequences that can assume similar 
structural motifs, which may carry out similar functions. For example, a helices and b sheets 
can be formed from a number of different amino acid sequences and are found in many 

One example given by Doolittle (1994) is of the remarkable similarity in fibronectin 
type III and immunoglobulin domains (cf., Fig 1). They are composed of series of three 


Figure la. Solution structure of the fibronectin Figure lb. Variable Light Chain Dimer of 

type III domain from Bacillus circulans WL-12 Ferritin Antibody (Nymalm et al, 2002). 

chitinase Al (Jee et al, 2002). 

and four stranded b sheets that are virtually identical in structure despite a lack of sequence 
similarity between these two molecules. 


In protein evolution, sequence divergence, rather than sequence convergence is the rule. 
In sequence convergence, one or more critical amino acids or an amino acid sequence of 
two proteins come to resemble each other due to natural selection. If the putative ancestral 
amino acids at a particular site were different in the ancestors of two proteins that now 
share an identical residue at that location, then convergent evolution may have occurred. 
The most frequently cited case of convergence and parallelism at the sequence level is the 
digestive enzyme lysozyme in a number of unrelated animals - the langur (a primate), the 
cow (an artiodactyls), and the hoatzin (a bird) - that have independently evolved the ability 
to utilize bacteria to digest cellulose (Kornegay, 1996; Zhang and Kumar, 1997). Specific 
residues have convergently evolved to allow digestion of cellulose-eating bacteria. 

3. Discussion and Conclusions 

We have assumed that natural selection seems to be powerful enough to shape terrestrial 
organisms to similar ends, independent of historical contingency. In an extraterrestrial en- 
vironment, it could be argued that the evolutionary steps that led to human beings would 


probably never repeat themselves; but that is hardly the relevant point; the role of con- 
tingency in evolution has little bearing on the emergence of a particular biological prop- 
erty (Conway-Morris, 1998). Besides, it can be said in stronger terms that essentially, 
evolutionary convergence can be viewed as a ‘re-run of the tape of evolution’, with end 
results that are broadly predictable. The inevitability of the emergence of particular bio- 
logical properties is a phenomenon that has been recognized by students of evolution for a 
long time. It is being referred in the present paper as ‘evolutionary convergence’. This phe- 
nomenon has been illustrated with examples taken exclusively from biochemistry, although 
its occurrence extends over other branches of the life sciences. The assumed universality of 
biochemistry suggests that in solar system missions, biomarkers should be selected from 
standard biochemistry. 

4. Acknowledgements 

The authors acknowledge with thanks the permission granted by Profs. Mark S. Johnson 
(Department of Biochemistry and Pharmacy, Abo Akademi University, Finland) and Masa 
Shirakawa (Graduate School of Integrated Science, Yokohama City University, Yokohama, 
Japan) for the use of the structures. AAA was supported by the TRIL Fellowship under the 
ICTP Programme for Training and Research in Italian Laboratories, Trieste, Italy. 

5. References 

Austin, D. F. (1998) Parallel and convergent evolution in the Convolvulaceae, In: P. Mathews and M. Sivadasan 
(eds.) Diversity and Taxonomy of Tropical Flowering Plants, Mentor Books, Calicut, India, pp. 201-234. 

Chela-Flores, J. (2003) Testing Evolutionary Convergence on Europa. International Journal of Astrobiology (Cam- 
bridge University Press), in press. 

Conway Morris, S. (1998) The Crucible of Creation. The Burgess Shale and the Rise of Animals, London, Oxford 
University Press, p. 202. 

Conway Morris, S. (2002) First Steps towards defining galactic niches. Paper presented at the lAU Symposium 
213 Bioastronomy 2002 Life Among the Stars. Summary of Proceedings, Hamilton Island, Great Barrier Reef, 
Australia July 8—12, Australian Centre for Astrobiology, Sydney, p. 12. 

Dawkins, R. 1983, Universal Darwinism, In: D.S. Bendall (ed.) Evolution from molecules to men,., London, 
Cambridge University Press, pp. 403^25. 

Doolittle, R. F. (1994) Convergent evolution: the need to be explicit. Trends Biochem. Sci., 19, 15-18. 

Eisthen, H.L. and Nishikawa K.C. (2002) Convergence: Obstacle or Opportunity? Brain Behav. Evol. 59 (5-6), 

Fontana, W. and Buss, L.W. (1994) What would be conserved if “the tape were played twice”? Proc. Natl. Acad. 
Sci. USA., 91, 757-761. 

Jee, J., Ikegami, T., Hashimoto, M., Kawabata, T., Ikeguchi, M., Watanabe, T and Shirakawa, M. (2002). Solution 
Structure of the Fibronectin Type III Domain from Bacillus circulans WL-12 Chitinase Al. J. Biol. Chem., 
277, 1388-1397. 

Komegay, J. (1996) Molecular genetics and evolution of stomach and nonstomachlysozymes in the hoatzin. J. 
Mol. Evol., 42, 676-684. 

Nymalm, Y., Kravchuk, Z., Salminen, T., Chumanevich, A. A., Dubnovitsky, A.P., Kankare, J., Pentikainen, O., 
Lehtonen, J., Arosio, P, Martsev, S. and Johnson, M.S (2002). Antiferritin VL homodimer binds human spleen 
ferritin with high specificity. J. Struct. Biol. 138(3), 171-186. 

Pace, N. R. (2001) The universal nature of biochemistry. Proc. Natl. Acad. Sci. USA 98, 805-808. 

Tramontano, A. (2002) Private communication. 

Zhang, J. and S. Kumar (1997) Detection of convergent and parallel evolution at the amino acid sequence level. 
Mol. Biol. Evol., 14, 527-536. 

A Mini Review 


The Hebrew University of Jerusalem, Home: P.O.B. 1132, Efrat 90435, 

I. Introduction 

Microorganisms occupy almost every habitable niche on Earth. They are abundant not 
only in “normal” environments but also thrive in very harsh habitats. These organisms, 
existing at the limits of life, have been designated “extremophiles.” They may be found 
thriving in very severe growth conditions (from our anthropocentric point of view). Among 
the extremophiles are representatives of all three domains of life (Bacteria, Archaea, and 

Life has existed on Earth at least for 3.5 to 3.8 billion years. Assumedly, the atmospheric 
conditions during the early period on Earth were different and more severe from those 
existing today. Life may have originated just below the Earth’s surface and/or within deep 
dark oceanic hydrothermal vents. 

Extremophilic microorganisms occupy almost every environmental niche, even those 
that are often considered to be totally inhabitable. These extremophiles may also serve as 
models for microbes that could perhaps live under the harsh conditions that exist in extrater- 
restrial environments. Celestial bodies that contain liquid water (as the main requirement 
for life) may harbor life. Among these places are Mars and the Jovian satellite, Europa. We 
should especially search for life on extrasolar Earth-like planets, where conditions may be 
suitable for life (as we know it). A review by Nisbet and Sleep (2001) covers some of the 
above aspects of early life. 

2. The Extreme Environments 

The study of the extremophiles and of organisms that live in habitats previously thought 
to be uninhabitable has become a major interest for those involved in the study of the 
origin of life. Although most extremophiles are Bacteria and Archaea, many species of 
Eukarya live at the edge of life’s normal environment (Roberts, 1999). Also, oxygenic 
photosynthetic microorganisms (such as algae, in addition to the cyanobacteria) thrive in 
extreme environments. In this short paper I will briefly survey a few major groups of 
extremophiles and the importance of the understanding of their biology for searching for 
life elsewhere in the Universe (see also the Astrobiology web site that covers most of the 


J. Seckbach et al. (eds.), Life in the Universe, 139 - 142 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


3. Some Extremophiles and their Habitats as Models for Astrobiology 

Microorganisms have been observed to grow in all ranges of temperature, from — 20°C 
(Junge et al., 2004; Thomas and Dieckmann, 2002) up to 113°C (Blochl et ah, 1997). 
The psychrophiles live in cold and freezing areas, while the thermophiles and hyperther- 
mophiles live in warm and hot environments, respectively. Most phylogenetic models pre- 
dict that the first microorganisms may have been hyperthermophiles (Rossi et ah, 2003; 
Seckbach, 1994b). Following the Hadean era. Earth’s subsurface remained hot due to the 
meteorite bombardments; the oceans might have been heated up to 100°C (Rossi et ah, 
2003).Hyperthermophiles could have been the first living pioneers within such hot envi- 
ronments, or the only survivors following such sterilizing hot events. It has been proposed 
that such hyperthermophiles may also serve as candidates for microorganisms in celestial 
bodies that may have similar physical conditions as occur in extremely hot environments on 
Earth. Hyperthermophiles may serve not only for scientific research but also for industrial 
application (Rothschild and Mancinelli, 2001). 

Organisms living in cold habitats are called psychrophiles. They are distributed in places 
such as the Arctic and the Antarctic, where sea-ice organisms thrive in the ice (Thomas and 
Dieckmann, 2002; Junge et ah, 2004). Other psychrophiles live in the permafrost of Siberia. 
Some microbes can resist a frozen period and may survive subzero temperatures, and then 
germinate under warmer conditions. Eurthermore, bacterial spores are almost immortal and 
can retain their viability for millions of years under harsh conditions and hnally be revived. 
Bacteria have been recovered and revived following a long stay on the moon and in space. 
They have tolerated severe cold, lack of an atmosphere, and high UV radiation and still have 
been revived upon returning to Earth. In Antarctic ice there are many planktonic organisms 
including bacteria, algae (most conspicuous are the pinnate diatoms) protists, flatworms and 
small crustaceans (Thomas and Dieckmann, 2002). Bacterial activity has been documented 
at — 20°C — making the limits of life on Earth wider. 

Thermophiles, or the heat loving microorganisms, are ubiquitously found in hot springs 
and hot locations, such as the Solfatara volcanic area near Naples, Italy. The red unicellular 
thermoacidophilic Cyanidium caldarium is an enigmatic alga (Seckbach, 1992. 1994a). 
This rhodophytan grows in very low pH areas, at temperatures up to 56-57°C. It thrives in 
media very well bubbled with pure CO 2 (Seckbach et ah, 1970). Its cohorts in the family 
Cyanidiacean cohabit the same elevated temperature and low pH environments (Seckbach, 
1992). Thermophilic cyanobacteria inhabit an even higher temperature range, living in 
neutral or alkaline hot springs at temperatures of up to ~70°C. Bacteria and Archaea are 
abundant in high temperatures and inhabit most hot environments. 

Among the hyperthermophiles are the prokaryotes. Bacteria and Archaea that have 
been observed distributed from 80°C to temperatures higher than 100°C. These microbes 
occur in deep-sea hydrothermal vents, including in black smoker chimney structures (Takai 
et ah, 2001). Stetter and his coworkers have determined the uppermost temperature of life in 
Pyrolobus fumarii at 1 13°C (Blochl et ah, 1997), and this organism can survive incubation 
in an autoclave at 121°C for over 1 hour. Such hyperthermophiles may have been the initial 
microbes that evolved in the depth of the hot oceans, or the only survivors in the primeval 
environment (Rossi et ah, 2003). In the depth of the subsurface and deep in the oceans these 
microbes could also have been protected from harmful UV radiation during the primeval 


era of Earth, as well as shielded from the meteorites’ impact during the early states of the 

The acidophiles thrive in lower ranges of pH (Seckbach, 2000) such as in sulfur hot 
springs, and in volcanic Solfatara soil (near Naples, Italy). On the other side of the pH scale 
are the alkaliphiles that live in alkaline environments, such as in the African soda lakes. 

The halophiles are organisms living in very salty environments, such as in salt lakes, salt 
mines or saline ponds sometimes containing saturated salt solutions. In the seas and oceans 
the concentration of the salts is 34 g per liter, while the Dead Sea may reach 10 times as much 
dissolved salts. Some halophiles (e.g., the green algaDunaliella salina) accumulate organic 
compounds, such as glycogen or (3 carotene. Its internal content of glycerol balances the 
external high osmotic pressure. High brine salinities may cause major dehydration stress 
for ice-trapped organisms. Square and triangular halophilic Archaea have been reported in 
salt media (Oren, 1999). A recent comprehensive volume on the halophilic world has been 
published by Oren (2002). 

Those organisms that are able to tolerate dry conditions are the xerophiles. Bacteria 
(or their spores) have known to last in desiccating conditions for many years. Bacillus 
sphaericus has been isolated from extinct bees trapped in 25-40 million year (Myr) old 
amber. Vreeland et al. (2000) claimed to have isolated a 250-Myr-old halotorelant bacterium 
from a salt crystal. 

Other microorganisms have been shown to resist UV radiation (e.g., Deinococcus 
radiodurans). The barophiles and piezophiles live under high pressures in the depths of 
the oceans (see hyperthermophiles, above) and deep underground. There are also microbes 
that consume oil spills in the oceans, grow in the presence of high concentrations of metal 
ions and even tolerate toxic compounds. 

On Earth no living organism can exist without liquid water. The search for extraterrestrial 
life should be “follow the water”: in any celestial body where there is liquid water there 
might be life. Meteorites from Mars that have landed on Earth have been reported to show 
some signatures of life, but the evidence has not been widely accepted. The NASA images 
of Mars suggest that in the past this planet had plenty of running water (e.g., rivers, lakes, 
canyons, oceans, etc.). The nature of the presumed nanofossils observed in ALH84001 is 
highly controversial, due to their petite size and laboratory-reconstructed artihcial minerals 
that have the same appearance (Reitner, 2004). No consensus has been reached on whether 
life exists or even existed on Mars. Early Mars may have been an eminently habitable place. 
Had life existed on Mars, the ejecta during the impact era could have carried one or more cells 
within a rock or meteorite to infect the planet Earth. Another promising heavenly body is 
Europa, the Jovian moon. Deep under its surface there is a lake of liquid water. If in the Vostok 
station in Antarctica the subsurface lake contains microorganisms, similar microbes may 
also exist under the surface of Europa. Subsurface water on Mars has been assumed to exist 
as subsurface brine aquifers, while in early time the water on Mars was free on the surface. 

Life may have existed on Venus within the early cytherean oceans; the possibility that 
life may have existed on the planet should therefore not be totally rejected (Seckbach 
and Libby, 1970). Terrestrial microorganisms can live in similar conditions as primordial 
Venusians under high CO 2 , elevated temperature, and even tolerate sulfuric acid. One such 
microorganism is Cyanidium caldarium (see above) (Seckbach, 1992; 1994a; Seckbach and 
Libby, 1970). 


4. Conclusions 

The extremophiles grow in very severe environments that have been considered until recently 
totally inhabitable. They occur in very harsh habitats, thus enlarge our knowledge about 
the limits of life on Earth. If some celestial bodies have liquid water and other conditions 
required for life, such extremophiles may exist there. 

5. References 

Blochl, E., Rachel, R., Burggraf, S., Hafenbradl, D., Jannasch, H.W. and Stetter, K. O. (1997) Pyrolobus fumarii, 
Gen. And Sp. Nov., represents a novel group of archaea, extending the upper temperature limit for life to 1 1 3 
degrees C. Extremophiles, 1: 14-21. 

Junge, K., Eicken, H. and Deming, J.W. (2004) Bacterial activity at —2 to — 20°C in arctic wintertime sea ice. 
Appl. Environ. Microbiol., 70: 550-557. 

Nisbet, N. G. and Sleep, N. H. (2001) The habitat and nature of early life. Nature, 409: 1083-1091. 

Oren, A. (1999) The enigma of square and triangular halophilic Archaea. In: J. Seckbach (ed.) Enigmatic 
Microorganisms and Life in Extreme Environments. Kluwer Academic Publishers, Dordrecht, The 
Netherlands, pp. 338-355. 

Oren, A. (2002) Halophilic Microorganisms and their Environments, vol. 5 of Cellular Origins, Life in Extreme 
Habitats and Astrobiology (COLE) Series editor J. Seckbach. Kluwer Academic Publishers, Dordrecht, The 

Reitner, J. (2004) Organomineralisation — an Assumption to understand meteorite-related bacteria-shaped carbon- 
ates. In: J. Seckbach (ed.) Origins: Genesis, Evolution and Diversity of Life. Kluwer Academic Publishers, 
Dordrecht, The Netherlands, in press. 

Roberts, D. M^^L. (1999) Eukaryotic cells under extreme conditions. In: J. Seckbach (ed.) Enigmatic Microor- 
ganisms and Life in Extreme Environments. Kluwer Academic Publishers, Dordrecht, The Netherlands, 
pp. 163-173. 

Rossi, M., Ciaramella, M., Cannio, R. Pisani, F. M., Moracci, M. and Bartolucci, S. (2003) Extremophiles 2002. 
J. Bacter. 183: 3683-3689. 

Rothschild, L.J. and Mancinelli, R.L. (2001) Life in extreme environments. Nature, 409: 1092-1 101 . 

Seckbach, J. (1992) The Cyanidiophyceae and the “anomalous symbiosis” of Cyanidium caldarium. In: W. Reisser 
(ed.) Algae and Symbioses: Plants, Animals, Fungi, Viruses, Interactions Explored. Biopress Ltd. Bristol, UK. 
pp. 339^26. 

Seckbach, J. (ed.) (1994a) Evolutionary Pathways and Enigmatic Algae, Kluwer Academic Publishers, Dordrecht, 
The Netherlands. 

Seckbach (2000) Acidophilic microorganisms. In: J. Seckbach (ed.) Journey to Diverse Microbial Worlds. Kluwer 
Academic Publishers, Dordrecht, The Netherlands, pp. 107-116. 

Seckbach, J. (1994b) The first eukaryotic cells — acid hot-spring algae: Evolutionary paths from prokaryotes to 
unicellular red algae via Cyanidium caldarium (PreRhodophyta) succession. J. Biol. Phys. 20: 335-345. 

Seckbach, J. and Libby, F. W. (1970). Vegetative Life on Venus? Or investigations with algae which grow under 
pure CO 2 in hot media at elevated pressures. Space Life Sci., 2: 121-143. 

Seckbach, J., Baker, FA. and Shugarman, PM. (1970) Algae thrive under pure CO 2 . Nature, 227: 744—745. 

Takai, K., Komatsu, T., Inagaki, F. and Horikoshi, K. (2001) Distribution of Archaea in a black smoker chimney 
structure, Appl. Environ. Microbiol. 67: 3618-3629. 

Thomas, D.N. and Dieckmann, G. S. (2002) Antarctic sea ice-a habitat for extremophiles. Science, 295: 641-644. 

Vreeland, R.H., Rosenzweig, W.D. and Powers, D.W. (2000) Isolation of a 250 million-year-old halotolerant 
bacterium from a primary salt crystal. Nature, 407: 897-900. 

Note: I thank Professors Julian Chela-Flores, Aharon Oren and Tobias Owen for their 
proofreading of this manuscript and providing practical revisions. 

V. Alternative Scenarios for the Origin 
and Evolution of Life 



Department of Animal Biology & Genetics, University of Florence, 
Via Romana, 17; 50125 Florence, Italy 

Abstract. Molecules which store genetic information (DNA and RNA) are central to all life 
on Earth. The formation of these complex macromolecules, and ultimately life, required spe- 
cific conditions, including the synthesis and polymerization of precursors (nucleotides), the 
protection and persistence of information polymers in a changing environment, and the expres- 
sion of the “biological potential” of the molecules, i.e. their capacity to multiply and evolve. 
Determining how these steps occurred and how the earliest genetic molecules originated on 
Earth is a problem that is far from being resolved. Recent observations on the synthesis of 
polynucleotides on clay surfaces, the resistance of clay-adsorbed nucleic acid molecules to en- 
vironmental degradation and the biological activity of clay-adsorbed DNA and RNA molecules 
suggest that mineral surfaces could have played a crucial role in the prebiotic formation of the 
biomolecules basic to life. 

I. Introduction 

All life forms on Earth today, and all life for which there is fossil evidence, are based on 
the DNA molecule, which is made up of nucleotides. It is the sequence of these subunits 
that supplies the language of life. These are the genes, which code for all information 
about a particular life form. The specific sequence of nucleotides is handed down from one 
generation to the next by DNA replication, thus ensuring the perpetuation of the “genetic 
information” on Earth. At present, we can say that the beginning of life coincided with 
the appearance of a nucleic acid-like polymer able to undergo evolution through processes 
of replication, mutation and natural selection. The formation of genetic material is thus 
the starting point for any discussion of the origins of life on our planet, and perhaps any 

The building of primordial genetic polymers entails at least four fundamental steps: the 
synthesis and availability of precursors (e.g. nucleotides), the joining of these precursors into 
macromolecules (e.g. polynucleotides), the protection of polymers against degradation (e.g. 
by cosmic and UV radiation), thus ensuring their persistence in a changing environment, 
and — finally — the expression of the “biological” potential of the molecule, i.e. its capacity 
to self-replicate and evolve. Determining how these steps occurred and how the primordial 
genetic molecules originated on Earth is a very difficult problem that still must be resolved 
(Lazcano and Miller, 1996). 


J. Seckbach et al. (eds.), Life in the Universe, 145 - 148 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


With regard to the first two steps — the synthesis of precursors of biological macro- 
molecules and their polymerization — classical research in this field has focused on pro- 
cesses in aqueous solutions, in fhe belief thaf building blocks of fhe biomolecules could 
be readily obtained by chemical reactions involving simple organic compounds present 
on Earth’s surface. However, the fact that the right components were present in primeval 
habitats is not sufficient by itself to explain the appearance of complex molecules. The 
creation of these macromolecules required the polymerization of single components. As 
biological polymers are generally formed by dehydration, it is difficult to conceive that 
complex macromolecules could have originated by random collisions in the presence of a 
high concentration of water, like that of a primordial ocean. In these conditions hydrolysis 
is favoured, not polymerization (Pace, 1994). 

This problem is exemplified by the properties of RNA. It is currently believed (Joyce, 
2002) that in an era indicated as the “RNA World”, the RNA molecule could have func- 
tioned both as genetic material and as an enzyme (“ribozyme”) (Doudna and Cech, 2002). 
The presence of the 2’-OH group in ribose, which renders RNA catalytic, also makes the 
molecule particularly susceptible to hydrolysis. Therefore, the very complex structure of 
RNA and its intrinsic instability make it very difficult to imagine the origin of a hypothetical 
RNA World in free solution. 

It has long been suggested that surface chemistry on clays or other minerals was involved 
in the prebiotic chemical evolution that culminated in the origin of life. In 1 95 1 , J.D. Bemal 
suggested that clay minerals could have bound organic molecules from the surrounding 
water, concentrating them and protecting biomolecules against destruction by high tem- 
peratures and strong radiation. In recent years, numerous observations have reinforced this 
hypothesis. Ferris et al. (1996) demonstrated the polymerization of oligonucleotides up to 
the length of a small ribozyme on montmorillonite clay. More recently, Huang and Ferris 
developed a new method for the synthesis of RNA oligomers in the presence of clays, in 
a “one step reaction” without the need of a primer (Huang and Ferris, 2003). Smith et al. 
(1998, 1999) provided a theory for the assembly of biopolymers on silica-rich minerals 
resembling zeolites. In addition, experimental data in the field of molecular microbial ecol- 
ogy have strengfhened fhe hypothesis of a surface-mediated origin of life. Studies carried 
out on the “fate” of DNA in soil habitats have indicated that DNA originating from dead 
or living cells can persist for a long time in the environment and still maintain its biologi- 
cal activity as a result of its interaction with clay particles (Stotzky et al., 1996). All these 
observations suggest that mineral surfaces could have played an important role in the forma- 
tion and accumulation of genetic molecules in primeval terrestrial habitats (Franchi et al . , 
1999), promoting their polymerization and allowing their persistence in an inhospitable 
environment like that of early Earth. 

Nevertheless, for some sort of RNA World to develop, genetic polymers not only had to 
accumulate, they also had to interact with surrounding molecules. In other words, genetic 
polymers must have been able to acquire new specialized functions (catalysis, informa- 
tion, etc.) in order to self-organize spontaneously into the first self-replicating “living” 

For these reasons, we decided to investigate the physical-chemical and biological char- 
acteristics of nucleic acid-clay complexes in order to better understand their possible role 
in the origin of life. 


2. Nucleic Acid-Clay Complexes 

Nucleic acid-clay complexes were obtained by reacting DNA and RNA with two clay 
minerals, montmorillonite (M) and kaolinite (K), as described by Franchi et al. (1999). 
They were extensively analyzed by different techniques to determine the nature of the 
interaction of the nucleic acids with the clay particles. X-RD showed that DNA molecules 
do not intercalate the Al-Si layers of the clays, indicating that the adsorption occurs primarily 
on the external surface of the particles, as also suggested by electron microscopy analysis. 
FT-IR spectra of clay-DNA complexes showed a change of the nucleic acid conformation, 
with a transition from the B to the A form, as a consequence of its adsorption on the 
mineral particles. Mono- and divalent cations take part directly in the adsorption/binding 
of nucleic acids on clay particles, acting as a “bridge” between the negative charges on 
the mineral surface and those of the phosphate groups of the genetic polymer. Double- 
stranded DNA needs higher cation concentrations than single-stranded DNA to establish 
an interaction with clay. This suggests that the number of strands in nucleic acid molecules 
was an important selection factor for their persistence in prebiotic habitats, influencing their 
adsorption/release by clay minerals (Franchi et al, 2003). 

Studies on the resistance of nucleic acids (DNA and RNA) to degradation have indi- 
cated that both chromosomal and plasmid DNA bound to montmorillonite and kaolinite 
are protected from the activity of endonucleases (Gallori et al, 1994). Similar results have 
been obtained for the RNase-A dependent degradation of 16S rRNA bound on clays. Ad- 
sorption of DNA on clay minerals also increases its resistance to UV radiation, as shown 
by a reduction of the number of pyrimidine dimers (T-T). 

The transition from the B to the A form of the DNA double helix could partially account 
for the increased resistance of nucleic acid-clay complexes to environmental degradation: 
the transformation makes the molecule less available to biotic and abiotic degrading agents. 

3. Biological Properties of Nucleic Acids Adsorbed on Clay 

Adsorption/binding of the DNA molecule on mineral particles does not prevent its bio- 
logical activity. Chromosomal and plasmid DNA bound to M and K retain the ability to 
transform competent bacterial cells for a long time, even after enzymatic digestion (Gallori 
et al, 1994). Moreover, clay-bound DNA can be enzymatically replicated and amplified 
outside the cellular context by the Polymerase Chain Reaction (PCR) (Vettori et al , 1996), 
confirming that biological information stored in DNA is not lost because of its adsorp- 
tion to clay. Results of reverse transcriptase and amplification (RT-PCR) of 16S ribosomal 
RNA from the bacterium Escherichia coli indicate that the same is true for adsorbed RNA 
molecules. These observations support the hypothesis that nucleic acid complexes could 
have acted as a “storage” of genetic information in primeval habitats. 

The possibility of further spontaneous organization was evaluated by studying the 
molecular reactivity of clay-adsorbed genetic polymers. Single-stranded RNA (Poly[A]) 
adsorbed on clay was able to recognize complementary molecules (Poly[U]) present in 
solution and to form double-stranded stretches (Poly[A] Poly[U]), showing that clay- 
adsorbed RNA molecules are able to establish specific interactions with surrounding 


biopolymers. Moreover, the catalytic activity of “hammerhead” rihozymes, i.e. self-cleavage 
of the molecule via transesterification (2’, 3’ cyclic phosphate) (Doudna and Cech, 2002), 
is currently being tested. Finally, the viroid PSTVd (Potato Spindle Tuber Viroid) is able 
to maintain its infectivity when adsorbed on montmorillonite and kaolinite, even after en- 
zymatic digestion. This is particularly important since viroids are the only nucleic acid 
molecules (RNA) known to undergo replication without DNA intermediates and without 
coding for proteins. These characteristics, together with the frequent presence of active 
ribozymes inside these particular RNA molecules, suggest that they may be relics of the 
previously cited “RNA World” (Diener, 2001). 

4. Conclusions 

The experimental results summarized above, together with previous observations of this and 
other research groups, suggest that the formation of a close association between prebiotic 
genetic molecules (whatever they were) and mineral surfaces could have been a crucial step 
in the origin of life on Earth. Clay minerals may not only have promoted the formation 
and accumulation of genetic material in prebiotic environments, but also allowed its self- 
organization into complex molecular systems that could self-replicate. 

5. References 

Bemal, JD (1951): The physical basis of life. Routledge & Kegan Paul, London. 

Diener, T.O. (2001) The viroid: biological oddity or evolutionary fossil?. Advances in Virus Research 57 , 
pp. 137-184. 

Doudna, J.A. and Cech, T.R. (2002), The chemical repertoire of natural ribozymes, Nature 418 , pp. 222-228; 

Ferris, J.P., Hill, A.R. Jr., Liu, R. and Orgel, L.E. (1996), Synthesis of long prebiotic oligomers on mineral surfaces. 
Nature 381 , pp. 59-61. 

Franchi, M., Bramanti, E., Morassi Bonzi, L., Orioli, P.L., Vettori, C. and Gallon, E. (1999), Clay-nucleic acid 
complexes: characteristics and implications for the preservation of genetic material in primeval habitats. 
Origins Life Evol Biosphere 29, pp. 297-315. 

Franchi, M., Ferris, J.P. and Gallon, E. (2003), Cations as mediators of the adsorption of nucleic acids on clay 
surfaces in prebiotic environments. Origins Life Evol Biosphere 33, pp. 1—16. 

Gallori, E., Bazzicalupo, M., Dal Canto, L., Fani, R., Nannipieri, P, Vettori, C. and Stotzky G. (1994), Transfor- 
mation of Bacillus subtilis by DNA bound on clay in non-sterile soil, EEMS Microbiol Ecol 15 , pp. 1 19-126. 

Huang, W. and Ferris, J.P. (2003), Synthesis of 35-40mers of RNA oligomers from unblocked monomers. A simple 
approach to the RNA World, Chemical Communications pp. 1458—1459. 

Joyce, G.F. (2002), The antiquity of RNA-based evolution. Nature 418 , pp. 214-221. 

Lazcano, A. and Miller, S.L. (1996), The origin and early evolution of life: prebiotic chemistry, the pre-RNA 
world, and time. Cell 85, pp. 793-798. 

Smith, J.V. (1998), Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealumi- 
nated zeolites and feldspars, Proc Natl Acad Sci USA 95, pp. 3370-3375. 

Smith, J.V., Frederick, PA. Jr., Parsons, I. and Lee, M.R. (1999), Biochemical evolution. III. Polymerization on 
organophilic silica-rich surfaces, crystal-chemical modeling, formation of first cells, and geological clues, 
Proc Natl Acad Sci USA 96, pp. 3479-3485. 

Stotzky, G., Gallori, E. and Khanna, M. (1996), In: A.D.L., van Elsas, Y.D. and de Brujin, F.J. (eds) Molecular 
Microbial Ecology Manual. Akkermans, , Dordrecht: Kluwer Academy Publishers, pp 1-28. 

Vettori, C., Paffetti, D., Pietramellara, G., Stotzky, G. and Gallori, E. (1996), Amplification of bacterial DNA 
bound on clay minerals by the random amplified polymorphic DNA (RAPD) technique, EEMS Microbiol. 
Ecol. 20, 251-260. 

Some Applications to the Origin of Life 


Department of Earth Sciences, University of Oxford, Parks Road, 

Abstract. Recent laboratory studies have shown that the polymerization of monomeric bases 
to form oligomeric nucleotide sequences, requires the presence of a solid catalyst such as the 
mineral montmorillonite. The formation in nature, at least of prehiotic precursor materials, may 
therefore also have required the presence of active mineral surfaces. The nature of reactions 
between organic precursors and mineral substrates is thus of considerable interest in studies of 
the origin of life. This paper reviews results obtained for the process of H2O chemisorption on 
MgO and Mg2Si04 surfaces from in situ synchrotron X-ray reflectivity studies, 'H-^^Si cross 
polarisation NMR spectra and ah initio calculations. The results show that the exact nature of 
molecular attachment and reactions on oxide and silicate surfaces can now be characterized 
with precision. Understanding the details of heterogeneous catalysis on mineral surfaces is a 
key step in understanding the processes that led to the origin of life. 

I. Introduction 

Recent studies of the polymerisation of bases to form oligonucleotide sequences have shown 
that, at least for purine and pyrimidine, silicate catalysts are required in the form of added 
montmorillonite (Ferris et al. 2003). In the presence of this clay mineral, up to at least 50- 
mer nucleotide sequences have been produced synthetically. The activity and complexity of 
hydroxy-Fe-montmorillonite surfaces have been highlighted in other recent work (Liao and 
Fraser 2002) and an increasingly strong case can be made for the involvement of condensed 
phase surfaces in catalysing the production of many prehiotic complex organic chemicals. 
The existence of chirality in crystalline phases such as quartz and calcite may also be 
important in selectively determining the production of particular prehiotic enantiomers 
(e.g. Hazen et al. 2001). Adsorption of chiral molecules onto a non-chiral substrate can even 
lead to the formation of new chiral facets and channels in a non-chiral substrate (Switzer et 
al. 2003). Around 72 amino acids have been identified in meteorites (Botta et al. 2001). The 
amino acid, glycine, has also been observed spectroscopically in interstellar space (Kuan et 
al. 2003) and studies of infra-red absorption indicate that interstellar dust contains material 
of Mg/Si ratio identical to olivine (Snow 2000). The existence of organic precursors in 
space and in meteorites, coupled with observations that silicate catalysts are required 
to assist laboratory-induced polymerisation, suggests that interactions between small 
molecules and mineral surfaces play a key role in chemical evolution and the origin of life. 


J. Seckbach et al. (eds.), Life in the Universe, 149 - 152 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 



^ Si MAS NMR, unhydrated mlnenils 

r Fo(q“) 

I MgjSiOa Fo 

MgSiO^ Bn 


p ProtoKn(Q^> 

CaMgSi20^ Di 





MgjSK)^ Fo, hydrated at 90 C 

SljN^ rotor ^ 

r F»(Q®) 

29si MAS NMR 




-55 -60 

-65 -70 -75 -80 -85 

Chemical Shift (ppm) 

-90 -95 

-50 -100 

Chemical Shift (ppm) 


Figure 1. MAS NMR spectra of unhydrated and hydrated forsterite, Mg 2 Si 04 , 

2. Reactions at the Olivine Snrface 

In several recent papers we have reported experimental and ab initio theoretical calculations 
of the precise nature of the interaction of water molecules with inorganic surfaces (e.g. 
Mejias et al. 1999, Xue et al. 2002, Wogelius et al. 1998). Forsteritic (approx F 090 ) olivine 
is a common constituent of meteorites and makes up, in low and high pressure forms, some 
45% of the Earth’s mantle in composition. In situ, glancing incidence X-ray reflectivity 
studies of reactions of H 2 O with polished F 092 surfaces show the development of a hydrated 
reaction layer tens of nm thick (Wogelius et al. 1998). 

To study the nature of this reacted surface more closely, MAS NMR measurements 
were carried out (Xue et al. 2002) on pure anhydrous and hydrated synthetic forsterite 
powders produced by sintering stoicheiometric amounts of natural abundance MgO and 
Si 02 at Ibar 1,500“C. The ^®Si spectra of the anydrous powders were determined and 
are shown together with those of synthetic enstatite and diopside in Fig.l. The un- 
ground forsterite powders were reacted with pure H 2 O at 90"C for two days and then 
washed and dried. 

^H-^^Si cross polarisation spectra select ^®Si resonances in Si atoms in immediate prox- 
imity to H atoms. The 'H-^®Si cross polarisation spectra are also shown in Fig. 1 and give 
a remarkable result. The single sharp ^^Si peak at —62 ppm of anhydrous forsterite and 
characteristic of Si atoms in isolated Q° tetrahedra remains unchanged in the spectrum of 
the bulk hydrated sample. However by selecting only surface Si atoms in the hydration zone, 
the 'H-^®Si cross polarisation spectrum shows polymerisation of the surface with only 
and groups present. Not only does exposure to water lead to formation of a hydrated 
surface, but the surface itself is active and polymerizes in response, forming a new surface 
composed of chain and sheet silicate groups. 

3. Ab Initio Calculations 

Theoretical and computational advances in the past decade have made possible accurate ah 
initio calculations of the energetics of systems of considerable complexity. In an attempt to 

Figure 2. AFM image of an MgO (100) cleavage surface etched lightly in water for 24 hours. The dissolution 
etch pits caused by the detailes of the reaction of water molecules with specific crystallographic planes. Scale 
bar is approximately 1.2 p,m. Note axes for orientation. 

Study the nature of the water attachment process in more detail, calculations were made of 
the hydration energies of MgO surfaces using density functional theory with plane-wave 
pseudopotentlals under GGA as described elsewhere (Mejias et al. 1999). This method gives 
bond lengths accurate to 2% and energies within lOkJ.mol”' in the system Mg0-Si02- The 
energetics of water molecule chemisorption on precisely defined crystallographic surfaces 
were calculated for the systems: MgO(lOO) - H 2 O; MgO(l 1 1) - H 2 O; MgO(l 10) - H 2 O; 
MgO(130) - H 2 O. The simple (100) cleavage surface of the rock-salt structure MgO is 
unstable to chemisorption with AE = -+-130 kJ.mol” ' . Monolayer chemisorption on ( 1 1 1 ), 
in contrast, is energetically favoured (AE = —20 kJ.mol'^). Hydration energies of (110) 
and (130) steps or terraces are not distinguishable from zero. 

An AFM image of a hydrated MgO surface is shown in Fig 2. The surface is a (100) 
cleavage surface exposed to pure water for 24 hours at approx 293K. This image shows 
that reaction of water molecules at the surface proceeds, not by dissolution on the (100) 
surface itself, but down (hkO) step edges and terraces on the surface as suggested by the 
calculations. H 2 O chemisorption is kinetically determined and the presence of defects such 
as steps on mineral surfaces may play a critical role in determining active sites for small 
molecule adsorption and catalysis. 

4. Conclusions 

The identification of organic molecules, including amino acids, in space (Kuan et al. 2003), 
together with the presence of suitable silicate and other inorganic dust particles (Snow 2000) 
indicates that abiotic precursors can form in extra-terrestrial conditions. The presence of 
active mineral surfaces may turn out to be crucial in the organization of small molecules 
to the point of carrying enough information to self-replicate (Ferris 2003) and recent work 
(Liao and Fraser 2002) shows the activity and complexity of hydroxy-Fe-montmorillonite 
surfaces. The importance of silicate lattice cages and surfaces as catalysts for organic 
chemical reactions is well-known (e.g. Rozanska et al. 2003) and zeolites filling vesicles in 
hydrated basalfs could also provide suitable and protected environments for the assembly, 
at least, of abiotic precursors. 


What is not clear is whether or not initial prebiotic synthesis took place on Earth under 
near-surface conditions or occurred elsewhere. There is strong geological evidence for the 
existence of liquid water and sedimentary processes on the Earth at 3.85 Ga. The Earth’s 
remaining and re-outgassed new atmosphere following the late heavy bombardment at 
around 4Ga must have contained large amounts of water vapour and mineral dust on the 
nano-particle scale. This mixture would have reached high altitudes near the top of the 
atmosphere where it would have been exposed to high levels of ultraviolet radiation and 
free-radical formation. Even this high-energy environment could have played an important 
role in seeding the surface with suitable organic precursors from which self-replicating 
molecules could form under lower temperature aquatic conditions (cf. Dobson et al. 2000). 
Such terrestrial sources are, of course, additional to any meteoritic introduction of organic 
material. As described above, it is likely that mineral surfaces played a central role in all 
these processes. 

5. Acknowledgements 

It is a pleasure to acknowledge the contributions of my co-workers at various times; in 
particular, Roy Wogelius, Keith Refson, Jose-Antonio Mejias, Andy Berry, Xian-yu Xue 
and Masami Kanzaki. 

6. References 

Botta, O., Glavin, D. P. Kminek, G. and Bada, J. L. (2001) Classification of Carbonaceous Meteorites Through 
Amino Acid Signatures? Lunar Planetary Science, XXXI 1. 

Ferris, J.P, Huang, W., Joshi, P, Miyakawa, S., Pitsch, S. and Wang, K-J.(2003) Catalysis and the emergence of 
the RNA world. Geochim.Cosmochim. Acta, 67 , A96. 

Dobson, C.M., Ellison, G.B., Tuck, A.F. and Vaida, V. (2000) Atmospheric aerosols as prebiotic chemical reactors. 
Proc. Nat. Acad. Sci., 97, 11864-11868. 

Hazen, R.M., Filley, T.R. and Goodfriend, G.A. (2001) Selective adsorption of L- and D-amino acids on calcite: 
Implications for biochemical homochirality. Proc. Nat. Acad. Sci., 98 , 5487-5490. 

Kuan,Y-J.,Chamley,S.B., Hui-Chun Huang, Tseng, W-L. and Kisiel, Z. (2003) Interstellar Glycine. The Astro- 
physical Journal, 593:848-867. 

Liao, L. and Fraser D.G. (2002) The adsorption of As onto hydroxy-Fe-montmorillonite complexes. Geochim. 
Cosmochim. Acta. 66, A455. 

Mejias, J.A., Berry, A.J., Refson, K. and Fraser, D.G. (1999) The Kinetics and Mechanism of MgO Dissolution. 
Chem. Phys. Letters. 314, 558-563. 

Rozanska X, van Santen RA, Demuth T, Hutschka F and Hafner J (2003) A periodic DFT study of isobutene 
chemisorption in proton-exchanged zeolites: Dependence of reactivity on the zeolite framework structure. J 
Phys Chem B 107 (6): 1309-1315. 

Snow, T.R (2000) Composition of interstellar gas and dust. J. Geophys. Res. AlO, 10239-1 1248. 

Switzer, J.A., Kothari, H.M., Poizot, R, Nakanishi S. and Bohannan, E.W. (2003); Enantiospecific electrodeposition 
of a chiral catalyst. Nature 425, 490-493. 

Wogelius R., Farquhar, M., Fraser D.G. and Tang C.C. (1998) Structural evolution of the mineral surface during 
dissolution probed with Synchrotron X-Ray techniques. In: B. Jamtveit and P. Meakin (eds) Growth and 
Dissolution in Geosystems, pp 1-17. 

Xue, X, Kanzaki, M. and Fraser D.G. (2002) The dissolution mechanism of Mg 2 Si 04 Forsterite: Constraints from 
^^Si and ^H MAS NMR. Geochim.Cosmochim. Acta. 66, A853. 



Department of Chemistry, Indian Institute of Technology Roorkee, 
Roorkee — 247 667, India 

Abstract. Interaction of ribonucleotides, namely 5'-AMP, 5'-GMP, 5'-CMP, and 5'-UMP with 
copper chromicyanide has been studied. Maximum adsorption was observed at neutral pH. 
The adsorption isotherms were found to be Langmuirian in nature. Copper chromicyanide was 
found to be effective adsorbent and purine nucleotides showed more adsorption than pyrimidine 
nucleotides. Infrared spectral studies suggested that the adsorption occurs due to interaction 
of phosphate moiety, N-1, N-3, and N-7 of ribonucleotide molecule and outer divalent copper 
ion present in the lattice of copper chromicyanide. Copper chromicyanide also has been found 
to be efficient in catalyzing the conversion of cysteine into cystine. The results of the present 
study support the hypothesis that the metal cyanogen complexes could have played important 
role in concentrating and stabilizing the biomonomers on their surfaces during the course of 
chemical evolution and could have acted as prebiotic catalyst. 

I. Introduction 

It is now widely accepted that a crucial step in chemical evolution on the earth involved the 
polymerization of important biomonomers such as amino acids, nucleotides, and pentose 
sugars which were formed from simple molecules under prebiotic environment, but till 
now it is not well established about how the biomonomers might have concentrated from 
their dilute aqueous solutions in primeval seas. However, one of the suggestions is that 
clays and other minerals have provided surfaces onto which small molecules could have 
been concentrated and might have undergone a class of reactions such as condensation, 
oligomerization, and redox reactions producing polymeric material from which life has 
emerged under prebiotic environment (Ferris and Kamaluddin, 1989; Ferris, 1999). 

It is generally accepted that the transition metal ions abundantly present in primeval 
seas, might have complexed with simple molecules available to them. It has been reported 
that cyanide ions were readily formed under prebiotic environment. Since cyanide ion 
is strong field ligand, it is reasonable to assume that cyanide ions might have formed a 
number of insoluble and soluble cyano complexes with transition metal ions abundantly 
present in primeval seas. Arrhenious has proposed the existence of ferro-ferricyanide in 
Anoxic Archean Hydrosphere. Water insoluble metal cyanogen complexes might have 
locally settled at the bottom of sea or at sea shore. We propose that these metal cyanogen 
complexes might have concentrated the biomonomers on their surface through adsorption 
processes and subsequently catalyzed a class of reactions of prebiotic relevance. 


J. Seckbach et al. (eds.), Life in the Universe, 153-156. 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Various metal ferrocyanides have been synthesized in our laboratory and their interaction 
with biomonomers such as amino acid, nitrogen bases and nucleotides have been studied 
suggesting their possible role in chemical evolution (Kamaluddin et ah, 1990; Alam and 
Kamaluddin, 2000). They have been found to be efficient in catalyzing reactions of prebiotic 
relevance (Alam et ah, 2000, 2002). We studied the interaction of 5'-ribonucleotides with 
copper chromicyanide to test its possible role in chemical evolution. 

2. Experimental 

Copper chromicyanide was synthesized from potassium chromicyanide by double decom- 
position method. Potassium chromicyanide was synthesized using Christensen’s method 
(Bigelow, 1946). 167 ml, O.IM potassium chromicyanide solution was slowly added to 500 
ml, O.IM copper nitrate solution with constant stirring. After 24 h reaction mixture was 
filtered, washed with water, dried, ground and sieved to 80-mesh size. Characterization 
of the copper chromicyanide was done by CHN analysis, TGA, IR and X-ray diffraction 

The adsorption of all the four ribonucleotides on copper chromicyanide was studied 
at pH 4.0, 7.0 and 9.0 by adding 5 ml of 2.8 x 10“"^ M ribonucleotide solutions to 25 mg 
adsorbent each time. The suspensions were shaken initially for 1 h and then allowed to 
equilibrate at 30°C with intermittent shaking. After 24 h the suspensions were centrifuged 
at 8000 rpm and the supernatant liquid was decanted. The amount of adsorbed ribonucleotide 
was estimated from the difference between their concentrations before and after adsorption 
spectrophotometrically. The equilibrium concentration of ribonucleotide and the amount 
adsorbed were used to obtain adsorption isotherms. 

3. Results and Discussion 

For the chromicyanides of divalent metal ion, a general formula M3[Cr(CN)e]2.nH20 has 
been reported, where represents an exchangeable divalent transition metal ion. The 
[Cr(CN)6]^“ ions possess an octahedral geometry in which Cr+^ is surrounded by six CN“ 
ligands and has electronic configuration of t^g. One of the t 2 g orbital has two electrons, 
second t 2 g orbital has one unpaired electron whereas the third t 2 g orbital remains empty 
because the electrons are filled against Hund’s rule in the presence of cyanide ligand which 
is strong field in nature. Although CN~ ligands bond with Cr through cr donation, Cr donates 
TT electrons present in its dir orbital to antibonding pir orbital of CN~ producing sufficient 
back bonding character. The transition metal chromicyanides generally exist in a polymeric 
lattice structure with [Cr(CN)6]^“ anions, in which another transition metal ions may be 
coordinated through the nitrogen end of the cyanide ligand. 


The preliminary adsorption studies were carried out over a wide pH range, and subse- 
quent studies were performed at neutral pH, which exhibited the maximum adsorption. 
The adsorption data obtained at neutral pH and over a concentration range of adsorbate 


(4 X 10 to 2.8 X 10 "^M) followed Langmuir adsorption isotherms. The trend of ad- 
sorption was found as below: 

5'-GMP > 5'-AMP > 5'-CMP > 5'-UMP 

At lower pH, the nucleotide molecule has both the negative and positive charges and as 
the pH increased the negative charge on the nucleotide molecule is increased. The adsorption 
is presumably related to the involvement of N-1, N-3 and N-7 of the base residues as well 
as dissociated phosphate group. At neutral pH, 5'-monophosphate nucleotides exist in dian- 
ionic form because both the protons of phosphate group are dissociated at neutral pH. Pyrim- 
idine nucleotides are able to form complex through its phosphate moiety only and purine 
nucleotides are able to form a bridging complex due to availability of the N-7 position present 
in addition to the phosphate moiety. Presence of N-7 as an additional interaction site in cases 
of purine nucleotides may be responsible for their greater adsorption with metal cations, 
therefore, 5'-AMP and 5'-GMP show greater adsorption than that of 5'-CMP and 5'-UMP. 

The nature of interaction between ribonucleotides and copper chromicyanide was in- 
vestigated in terms of infrared spectral studies of adsorption adducts. A shift towards higher 
wavelength in the characteristic frequencies of ribonucleotides was observed, indicating the 
interaction between ribonucleotides and copper chromicyanide. The typical strong bands in 
the region 950-1150 cm“' are due to presence of ribose residue and change negligibly after 
adsorption. It suggests that ribose residue is not interacting with metal chromicyanides. A 
remarkable shift was observed in characteristic frequencies of purine nucleus and phos- 
phate groups of ribonucleotides, which suggested probable involvement of N-1, N-3, N-7 
and phosphate groups. Typical infrared frequencies of copper chromicyanide were almost 
unchanged suggesting that the ribonucleotide molecules do not enter into the coordina- 
tion sphere of copper chromicyanide by replacing the cyanide ion. Further the insertion of 
ribonucleotide in the coordination sphere of copper chromicyanide. 


The thiol group of cysteine was found to be readily oxidised to disulphide group by copper 
chromicyanide. 10 ml, O.OIM cysteine solution was reacted with 25 mg of copper chromi- 
cyanide. After 24 h, insoluble product was deposited which on analysis with ir, and uv 
showed disulphide bond formation. No reaction took place in the absence of the copper 

4. Conclusion 

The results of the present study support the postulate that the metal cyanogen com- 
plexes could have provided their surface onto which the biomonomers might have con- 
centrated from their dilute aqueous solutions during the course of chemical evolution. 
The biomonomers so concentrated have been protected from degradation and might have 
undergone a class of reactions such as condensation, oligomerisation and polymersation 
producing the biopolymers. Thus metal cyanogen complexes played an important role as 
prebiotic catalyst. 


5. Acknowledgements 

This research work was sponsored hy Indian Space Research Organisation, Bangalore 

6. References 

Alam, T., Gairola, R, Tarannum, H., Kamaluddin and Kumar, M.N.V. R. (2000) Conversion of Aniline to their 
Oligomers by Copper hexacyanoferrate(II), Indian J. Chemical Technology, 7, 230-235. 

Alam, T. and Kamaluddin (2000) Interaction of 2- Amino, 3-Amino and 4-Aminopyridines with Nickel and Cobalt 
Ferrocyanides, Colloids Surf, 162, 89-97. 

Alam, T., Tarannum, H., Ali, S.R. and Kamaluddin (2002) Adsorption and Oxidation of Aniline and Anisidine by 
Chromicyanide, J. Colloid Interface Science, 245, 251-256. 

Biegelow, J.H. (1946) Potassium hexacyanoferrate(III). In: Inorganic Synthesis, Vol. II, ed. W.C. Femelius, Mc- 
Graw - Hill Book Company, Inc., Printed in the United States of America, 203. 

Ferris, J.P. (1999) Prebiotic Synthesis on Minerals: Bridging the Prebiotic and RNA Worlds, Biol. Bull, 196, 

Ferris, J.P. and Kamaluddin (1989) Oligomerization Reactions of Deoxyribonucleotides on Montmorillonite Clay: 
The Effect of Mononucleotide Structure on Phosphodiester Bond Formation, Origins Life Evol. Biosphere, 
19, 609-619. 

Kamaluddin, Nath, M., Deopujari, S. W. and Sharma, A. (1990) Role of Transition metal Ferrocyanides(II) in 
Chemical Evolution, Origins Life Evol. Biosphere, 20, 259-268. 

Implications in the Availability of Soluble Phosphate in Abiotic Environments 


^Mineral Technology Centre (CETEM), MCT/BRAZIL; ^Chemistry 
Institute / Federal University of Rio de Janeiro / UFRJ-BRAZIL); 
^Physics Institute / UFRJ; Carlos Chagas Filho Biophysics Institute / 

I. Introduction 

It is well known that co-precipitation of soluble Fe-oxide precursors with reactive phosphate 
is the dominant mechanism responsible for the low concentrations of this organic molecule in 
contemporary aqueous media. The formation of Fe-oxide precursors requires free oxygen 
molecules. This feature is well established and it is a common observation that reactive 
phosphate is more abundant in anoxic, i.e., non-oxidizing aqueous media (Van Cappellen 
and Ingall, 1996). 

As noted by Stanley Miller and Harold Urey, the major overall chemical change in 
the geological scale is the transition from a reducing/neutral to the contemporary oxidizing 
atmosphere (Miller and Urey, 1959; Cloud, 1972; Kasting, 1993; Holland, 2002). This leads 
to the obvious conclusion that the major contemporary trapping mechanism could not have 
been a relevant process at the early stages of chemical evolution. 

Since the pioneer proposals by Bernal and Ponnamperuma (Bernal, 1951; 
Ponnamperuma et al., 1982), minerals that can mediate phosphate binding have been con- 
sidered in anoxic abiotic scenarios. A survey of these condensation reactions is beyond 
the scope of this report. We shall focus our attention to the mineral pyrite [FeSa]. Studies 
of this mineral have been intensified with the original work of Wachterhauser in the early 
1990’s (Wachtershauser, 1992). His model of an autotrophic process converting ferrous 
ions and hydrogen sulphide into pyrite induced investigations in environmental conditions 
simulating those near the hydrothermal vents at the mid-ocean ridges. 

Pyrite formations are common features in these hydrothermal sites (Seyfried, Kang 
Ding, and Berndt, 1991; Shock, 1992; Rona and Scott, 1993; MacLeod et al., 1994). It 
has been shown that pyrite reactive surfaces have a strong affinity to reactive phosphate 
(Bebie and Schoonen, 1999; Vieyra, et al., 2003). Estimates support the expectations that 
a significant volume of the oceans circulates in short time scale through the hot basalt and 


J. Seckbach et al. (eds.), Life in the Universe, 157 - 160 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


up through black smokers (Pilson, 1998). It is therefore reasonable to assume that soluble 
orthophosphate present in the primitive sea could complex with pyrite formations of the 
hydrothermal springs. 

We report in this communication experimental results supporting the conjecture that 
in this particular scenario orthophosphate could be released from pyrite formations. The 
required mechanism would be based on possible fluctuations of pH-factor and ionic concen- 
trations common to this particular environment. We propose that these mechanisms could 
be triggered by the dynamics of water streams through the hydrothermal vents. 

2. Experimental 

Details on the experimental settings for both the electrophoresis and the sorption/desorption 
determinations are given elsewhere (Monte et ah, 2003; Vieyra et ah, 2003). A surface 
treatment removed oxide, carbonate, and silicate impurities from the pyrite particles. The 
net negative-charge coverage of these particles decreases with the acidity of the aque- 
ous medium. This is due to the attachment of protonic charges onto the pyrite surface. 
Thus, the effective net charge of pyrite particles can be modulated in anoxic media. Our 
electrophoresis results indicate that the ions SO 4 - reported to exist in the emissions of 
hydrothermal vents - can also attach to the Pyrite surface. This is a specific sorption of 
sulphate ions - not electrostatic - for it is known that the net surface charge of Pyrite is 

The data shown in Figure 1 were obtained with suspensions of pyrite particles in an 
aqueous media simulating a primitive sea. The different pH- values used are shown in the 
figure. The arrow in this figure draws attention to the fact that the sampling procedure pre- 
cluded observations at very short time intervals. It also highlights that an efficient desorption 
process takes place in mild alkaline medium. It is observed that the acidity of an aqueous 
medium simulating a primitive sea affects the orthophosphate affinity to pyrite. A change 

Figure 1. Pi adsorption in more acidic and in mildly alkaline seawater. 


from an acidic to mild alkaline environment decreases the effective pyrite affinity to the 

Figure 2 clearly shows that sulphate ions can also affect the orthophosphate attachment 
to pyrite particles. In contrast, the results obtained with magnesium and sodium chloride are 
given as a comparative reference. The arrow indicates that the sampling procedure limits 
the time resolution of the assays. 

3. Conclusion 

We are proposing possible mechanisms that could have mediated the availability of reac- 
tive phosphate in special abiotic anoxic environments. In these environments, alternative 
phosphate condensation mechanisms would not have to compete with the dominant trap- 
ping process of modern eras: phosphate co-precipitation with Fe/Al-oxide precursors. We 
have shown that orthophosphate binding to pyrite can be modulated by alterations of the 
surrounding aqueous medium. It is suggested that short-duration perturbations affecting 
the acidity or the ionic composition of the surrounding media near the hydrothermal vents 
could have provided these specials niches with bursts of reactive phosphate. This opens 
new possibilities for models of molecular evolution that could use the well-known collec- 
tive process of phosphate co-precipitation onto mineral surfaces. The onset of this process 
requires concentrations of reactive phosphate beyond its equilibrium value. 

4. Acknowledgements 

This work was supported by grants from the Brazilian Agencies CNPq, FINEP PRONEX, 
EAPERJ, and of the FUJB Foundation. The authors are grateful for very constructive com- 
ments of anonymous reviewers. 


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fluids at mid-ocean ridges, Geochim. Cosmochim. Acta 55 , 3559-3580. 

Shock, E. L. (1992) Chemical Environments of Submarine Hydrothermal Systems, Orig. Life Evol. Biosph., 22 , 

Van Cappellen, P. and Ingall, E. D. (1996) Redox stabilization of the atmosphere and oceans by phosphorus-limited 
marine productivity. Science 271 , 493—496. 

Vieyra, A., Tessis, A. C., Pontes-Buarque, M., Bonapace, J.A.P, Monte, M.B.M., Amorim, H. S. de, and Souza- 
Barros, F. de (2003), Catalysis of nucleotide hydrolysis by pyrite: possible role of reactive surfaces in prebiotic 
energy interconnection. This proceedings. 

Wachtershauser, G., (1992) Groundworks for an evolutionary biochemistry: the iron-sulphur world. Prog. Biophys. 
molec. Biol. 58 , 85-201. 





^Instituto de Biofisica Carlos Chagas Filho/UFRJ, Rio de Janeiro, Brazil, 
^Centro de Ciencias Biologicas e da Saiide, Universidade Estdcio de Sd, 
Rio de Janeiro, Brazil, ^Instituto de Qui'mica/UFRJ, Rio de Janeiro, Brazil, 
^Centro de Tecnologia Mineral/MCT, Rio de Janeiro, Brazil and 
^Instituto de Fi'sica/UFRJ, Rio de Janeiro, Brazil 

1. Introduction 

Metal sulfides have been proposed as physical support for primitive bidimensional 
metabolism and chiral discriminators. There are controversial data about the possibly cou- 
pling between the exergonic pyrite syntheses and the endergonic amino acids syntheses 
in pyrite pulled metabolic-like processes. However, a role in adsorption and catalysis in- 
volving biomonomers - such as nucleotides - cannot be ruled out in an especial aqueous 
scenario. In an aqueous environment with a vast reservoir of reducing power in the form 
of, especially, iron (II) and sulhde within and beneath the crust. Our hypothesis is that 
ancient minerals such as pyrite could have played a role in concentrating mononucleotides 
and in determining their catalytic routes in later periods, when polynucleotides appeared 
and evolved (Tessis et ai, 1999). Pyrite - as well as other sulhdes - could have partic- 
ipated in nucleotide adsorption and in primitive phosphoryl transfer reactions in the less 
drastic conditions that prevail away from the hot hydrothermal vents, the big sources of 
starting molecules. In this presentation, we shall briefly comment about our results on the 
following themes: 1) Adsorption of mononucleotides (AMP and ADP) onto untreated and 
acetate-treated samples of pyrite in which soluble Fe®+ ions were removed; 2) The influ- 
ence - on nucleotide adsorption - of the previous adsorption onto the crystal of an oxo acid 
that could have appeared near the mineral and modified its surface properties (acetate can 
be formed onto the surface of mixed iron nickel sulfides at high temperature and pressure 
[Huber and Wachtershauser, 1997]); 3) The role of the interface. In some models, the two- 
dimensional system represented by a mineral surface would be in a seawater environment 
having a passive role. The actual conditions prevailing when sulfur materials are in contact 
with salt solutions are quite complex. The very reactive iron-sulfide immersed in a solution 
resembling a primitive ocean generates a continuously changing interface with ionic gradi- 
ents and formation of different oxide layers; 4) Hydrolysis of ATP adsorbed onto pyrite. 


J. Seckbach et al. (eds.), Life in the Universe, 161 - 164 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Results and Discussion 

In a recent paper (Pontes-Buarque et ai, 2001), assays with [^"^C]acetate show that the oxo 
acid is firmly and almost completely adsorbed onto the surface of pyrite. When the solution 
containing the ['"^C]acetate-coated pyrite samples was removed and replaced by artificial 
sea water, loss of pyrite-bound radioactivity to the medium after was barely detectable, indi- 
cating that acetate remains firmly attached to the mineral. Moreover there is no displacement 
of labeled acetate after removal of the supernatant and resuspension of ['"^Clacetate-coated 
pyrite in unlabeled acetate solutions, indicating that interaction between the oxo acid and the 
surface can be considered irreversible. The pyrite/solution interface when acetate-coated 
pyrite is resuspended in artificial (primitive) seawater could have been important in the 
modulation of an early, starting metabolism onto Fe/S mineral surfaces. The interface lies 
between the bulk pyrite and the outer aqueous medium and has two layers. The inner layer, 
known as the Stern layer, is made of hrmly attached ions such as acetate; the outer inter- 
face, characterized by the diffuse ionic gradients, is much thicker than the Stern layer. It is 
expected that an increase of both ionic or molecular species concentrations that can attach 
to the mineral surface results in the decrease of the Stern layer thickness and vice versa, 
thus modulating the interaction of ancient metabolites with the Fe/S minerals. It is clear 
that in this complex and interactive system, a large variety of processes able to continuously 
change the composition of the intermediate layers could had been changed, in several direc- 
tions, extant metabolic reactions catalyzed by minerals. The acetate-induced modifications 
of the interface could have been modified, for example, the adsorption of mononucleotides 
onto Fe/S in primeval seas, in mildly alkaline environments such as found in the warm, 
less drastic scenarios away the hot hydrothermal vents. The enhancement of nucleotide 
adsorption due to the presence of acetate can be seen in two completely different adsorption 
isotherms of AMP onto pyrite in two extreme conditions: in a acetate-dominant solute and in 
acetate-free primitive sea water. In a concentrated acetate medium the adsorption is greatly 
enhanced at low AMP concentrations, contrasting with the one observed in an acetate-free 
primeval solution. Therefore, the adsorption mechanism is highly cooperative due to the 
presence of acetate. In contrast AMP adsorption is very low in the absence of acetate. Only 
when additions of nucleotide are in the millimolar range, a self-induced adsorption mecha- 
nism clearly sets in. In conclusion, there is a clear-cut different behavior due to a different 
coating of the mineral. It is clear that high nucleotide implies in a greater possibility of 
polymerization induced by acetate, the universal precursor of carbon compounds in living 
systems. Acetate also enhances ATP adsorption (Tessis et ai, 1999). Adsorption is faster 
and complete when the crystals are previously treated with an acetate solution, separated 
and then supplied with ATP-containing artificial sea water. Again, the effect of coating 
pyrite with acetate promotes an increase in the adsorption capacity of pyrite, favoring the 
interaction of the nucleotide with the mineral surface. This experiment was carried out in 
the presence of iron oxides onto the surface of pyrite. When the surface oxides are removed 
with hydrofluoric acid and the experiments are done in the absence of O 2 , the levels of 
adsorbed ATP attained the same maximal values with and without pretreatment of pyrite 
with acetate. It is known that in the presence of O 2 pyrite is oxidized, first producing Fe^+; 
Fe^+ is further oxidized to Fe^+, and then Fe(OH )3 forms. Acetate can form complexes 
with Fe^+ and these complexes are stable even at high temperatures. Thus it is plausible 
to postulate that acetate could have had another role besides that of providing a source of 


carbon after its formation in hydrothermal vents. The flow of sulfides to cooler and more 
superficial regions away from the main ridges was probably as high in primitive eras as 
they are in the present (Corliss, 1990). In these mild and distant regions, the presence of 
acetate strongly bound to the surface of sulfide minerals could have favored adsorption of 
nucleotides by preventing the formation of iron hydroxides, even in the presence of the 
dissolved O 2 formed by photolysis of water. 

In contemporary living systems ATP hydrolysis is the key exergonic reaction and ADP 
is also an energy donor in Archaea (Kengen et ai, 1995). It was, therefore, interesting to 
test the hypothesis that in an ancient scenario in which ATP and pyrite were present, the 
mineral could have been able to catalyze phosphoryl transfer reactions involving adsorbed 
nucleotides (Tessis et ai, 1999). The acetate-coated pyrite suspended in artificial seawater 
promotes breakdown of the ( 3 , 7 - and the a,(3-phosphoanhydride bond of ATP adsorbed 
on its surface. The ATP adsorbed onto acetate-treated pyrite is sequentially cleaved by 
the mineral. ATP undergoes progressive hydrolysis to ADP and AMP (whereas the nu- 
cleotide concentration in artificial sea water remains unchanged in the absence of mineral). 
ATP and ADP hydrolysis are not the result of Fe^+-catalyzed hydrolysis in solution since 
ATP was totally adsorbed and soluble Fe^+ ions were removed by the acetate washing. 
Pyrite-catalyzed hydrolysis of ATP and ADP and their reversal are second-order sequential 
reactions. The disappearance of ATP, the biphasic time course of ADP formation and the 
accumulation of AMP can be described by exponential equations obtained with a model 
in which ATP hydrolysis is complete and ADP coexists in equilibrium with AMP (free 
energy change of ADP hydrolysis as low as -3.5 kJ/mol instead of -35 kJ/mol for ATP 
hydrolysis). This difference may be due to differences in solvation when polyphosphate 
chains of different length are attached to the acetate-coated pyrite surface. This observation 
means that phosphorylation of AMP to ADP is thermodynamically favored onto the surface 
of pyrite minerals in which two-carbon organic fragments are attached. The reversibility of 
the ADP hydrolysis in iron-sulfide mineral surfaces might have been an evolutional pressure 
factor that allowed the utilization of this nucleotide by very primitive organisms (Kengen 
et ai, 1995). In addition, pyrite surface exhibits specific properties in adsorption and catal- 
ysis that could have been relevant in chemical evolution: 1) It needs divalent cations for 
the attachment of phosphoryl groups but not for carboxylates; 2) It catalyzes hydrolysis 
of phosphoanhydride bonds but not of ester-phosphates; 3) It can selectively change the 
free energy of hydrolysis of the same chemical bond. Since phosphates can also catalyze 
the synthesis of ADP from AMP (Tessis et al, 1995), a varied assemblage of minerals in 
aqueous environments could have acted as adsorbants and catalysts of phosphorylations 
and energy conservation in primordial eras (Vieyra et al, 1995). 

3. Conclusions 

The results presented support the view that surfaces of iron-sulfide minerals, implicated 
in several primitive processes (Russell et al, 1994), could have participated in catalytic 
reactions involving phosphoanhydride bonds. The reactions occurring on those primitive 
interfaces, could have been modulated by the presence of hydrocarbon molecules formed 
in neighboring areas. More evolved energy-transducing systems could have taken over the 
hydrolytic properties of pyrite minerals and coupled them to energy-requiring processes. 


4. Summary 

There is an extensive literature on the possible roles of minerals in the chemical evolution of 
life. Minerals have considered in: a) processes that would discriminate molecular chirality; 
b) condensation reactions of biomolecular precursors; c) biochemical templates; d) pre- 
biotic catalysis; e) autocatalytic metabolism. This is the case of metal sulfides, especially 
iron sulfides, including pyrite. In this paper we present results showing that pyrite adsorbs 
nucleotides and that this process is modulated by acetate - which is considered a primi- 
tive carbon donor - and by the size and composition of the interface of the mineral with 
the aqueous environment. Moreover, pyrite exhibits specificity towards phosphoanhydride 
linkage but not for ester phosphates. 

5. References 

Corliss, J. B. (1990) Hotsprings and the origin of life, Nature 347 , 624. 

Huber, C. and Wachtershauser, G. (1997) Activated acetic acid by carbon fixation on (Fe,Ni)S under primordial 
conditions, Science 276 , 245-247. 

Kengen, S. W. M., Tuininga, J. E., de Bok, F. A. M. Stams, A. J. M. and de Vos, W. M. (1995) Purification 
and characterization of a novel ADP-dependent glucokinase from the hyperthermophilic archean Pyrococcus 
furiosus, J. Biol. Chem. 270 , 33453-33457. 

Pontes-Buarque, M., Tessis, A. C., Bonapace, J. A. R, Cortes-Lopes, G., Souza-Barros, F. de and Vieyra, A. (2001) 
Modulation of adenosine 5'-monophosphate adsorption onto aqueous resident pyrite: potential mechanisms 
for prebiotic reactions. Origins Life Evol. Biosphere, 31 , 343-362. 

Russell, M. J., Daniel, R. M., Hall, A. J. and Sherringham, J. A. (1994) A hydrothermally precipitated catalytic 
iron sulphide membrane as a first step toward life, J. Mol. Evol. 39 , 231-243. 

Tessis, A. C., Salim de Amorim, H., Farina, M., de Souza-Barros, F. and Vieyra, A. (1995) Adsorption of 5'-AMP 
and catalytic synthesis of 5'-ADP onto phosphate surfaces: correlation of solid matrix structures. Origins Life 
Evol. Biosphere 25, 351-373. 

Tessis, A. C., Penteado-Fava, A., Pontes-Buarque, M., Amorim, H. S. de, Bonapace, J. A. R, Souza-Barros, F. de 
and Vieyra, A. (1999) Pyrite suspended in artificial seawater catalysis hydrolysis of adsorbed ATP: enhanced 
effect of acetate. Origins Life Evol. Biosphere 29, 361-374. 

Vieyra, A., Gueiros-Filho, F, Meyer-Femandes, J. R., Costa-Sarmento, G. and Souza-Barros, F. de (1995) Re- 
actions involving carbamyl phosphate in the presence of precipitated calcium phosphate with formation of 
pyrophosphate: a model for primitive energy-conservation pathways, Origins Life Evol. Biosphere 25 , 335- 

VI. Cosmological and Other Space Science 
Aspects of Astrobiology 

Clues from studies of Damped Ly a galaxies 


Osservatorio Astronomico di Trieste — I.N.A.F.Italy 

1. Introduction 

The process of planet formation is poorly understood, even for stars of the solar vicinity. The 
key factors that govern this process need to be identified if we wish to understand whether and 
how planet formation takes place in other galaxies and in other epochs. Interstellar dust may 
play a key role in this context. Proto-planetary disks form from the sedimentation of the left- 
over material of the parent interstellar nebula which gives birth to the central star. The dust 
of the nebula accumulates in the midplane of the disk and, according to accretion theories, 
leads to the formation of planetesimals (Lissauer 1993). The quantity of dust present in the 
nebula prior to the formation of the central star can affect the efficiency of planetesimal (and 
planet) formation. In this contribution, evidence is presented for a deficit of dust in galaxies 
observed during their early stages of evolution. The study concerns a particular class of 
quasar absorption-line systems, called Damped Lyman ot (DLA) systems, associated with 
gas-rich galaxies observed at look-back times up to ~ 12 billion years ago. The deficit of dust 
in DLA galaxies is briefly discussed in the context of planet formation in the early universe. 
More details on DLA systems are presented in a separate contribution in these Proceedings. 

2. Dust and Planetesimal Formation at Very Low Metallicity 

The metallicity and dust content of DLA systems can be estimated from the abundances 
of volatile and refractory elements, such as Zn and Fe, respectively. In particular, one can 
derive the fraction of atoms of iron in dust form, fpe, which is essentially a dust-to-metal 
ratio by number (Vladilo 2002). In the course of chemical evolution the dust is expected to 
track the metals and, therefore, the dust-to-metal ratio should be roughly constant. Contrary 
to this expectation, we find that the dust-to-metal ratio increases with metallicity, with a 
severe deficiency of fpe at metallicity ~ 10“^ the solar level (Vladilo 2004). Given the virtual 
absence of dust, we wonder whether circumstellar disks can still create planetesimals at very 
low metallicity. In fact, the absence of a microscopic solid component in the disk-feeding 
material could dramatically delay the planetesimal formation; if this delay is larger than the 
life time of the disk (~ 10® / ~ 10^ years), planet formation would be inhibited. For instance, 
for conditions typical of the solar nebula, e-folding sedimentation times can easily be as high 
as ~ 10® years for 1 |jLm grains, and several e-foldlng times are required to produce a thin layer 
in which the dust and gas density are comparable, a minimum requirement for planetesimal 


J. Seckbach et al. (eds.), Life in the Universe, 167 - 168 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


formation (Lissauer 1993). To reduce these times one needs to invoke collisional growth of 
pre-existing grains during their descent to the midplane of the disk (Weidenschilling 1980). 
The scarcity of pre-existing dust grains at low metallicity may prevent collisional growth 
and make the huild-up of the critical dust density for planetesimal formation impossible 
within the life time of the disk. If we require at least ~50% of iron atoms to be in dust form 
(fpe > 0.5) in order to reduce the sedimentation time, we derive a metallicity threshold from 
the trend between fpe and metallicity observed in DLA galaxies (Vladilo 2004). With few 
exceptions, we hnd that a metallicity [Fe/H] >—1.5 dex is required so that fpe > 0.5. Below 
this threshold, which should be interpreted in a statistical sense, we argue that planetesimal 
formation may be exceedingly delayed and planet formation inhibited. 

3. Conclusions 

The very low fraction of dust found in DLA galaxies of low metallicity suggests a possible 
scenario for inhibition of planetesimal formation; the scarcity of pre-existing dust grains 
may yield sedimentation times exceeding the life-time of proto-planetary disks. In order 
to reduce the sedimentation time, a minimum fraction of metals must be in dust form. 
Model computations are required to define this minimal dust fraction in terms of physical 
quantities and metallicity. Efforts to relate the efficiency of planetesimal formation to the 
dust-to-gas ratio are already under way (e.g. Youdin & Shu 2002). If we adopt fpe > 0.5 as 
the minimal dust fraction of iron atoms, we obtain a metallicity threshold [Fe/H] > — 1.5 
dex for planetesimal formation. With this criterion planets should be rare in DLA galaxies 
at redshift z > 2. The metallicity limit proposed here is less stringent than the threshold 
[Fe/H] > —0.3 dex proposed by Gonzalez et al. (2001) for the formation of habitable 
planets. Taken at face value, these limits indicate that the interval — 1.5 < [Fe/H] < —0.3 
is characteristic of non-habitable planets. The discovery of a planet in the globular cluster 
M4 (Sigurdsson et al. 2003) may provide the hrst example of a non-habitable planet in this 
metallicity interval. 

4. References 

Gonzalez, G., Brownlee, D., and Ward, P. (2001) The Galactic Habitable Zone: Galactic Chemical Evolution, 
Icarus 152, 185-200 

Lissauer, JJ. (1993) Planet Formation, Ann. Rev. Astron. Astrophys. 31, 129-174 

Sigurdsson, S., Richer, H.B., Hansen, B.M., Stairs, I.H., Thorsett, S.E. (2003) A Young White Dwarf Companion 
to Pulsar B1 620-26: Evidence for Early Planet Formation, Science, 301, 193-196 

Vladilo, G. (2002) Chemical abundances of damped Ly alpha systems: A new method for estimating dust depletion 
effects, Astrophys. 391, 407^15 

Vladilo, G. (2004) The Early Build-up of Dust in Galaxies: A Study of Damped Lyman a Systems (work in 

Weidenschilling, SJ. (1980) Dust to planetesimals — Settling and coagulation in the solar nebula, Icarus 44, 

Youdin, A.N., and Shu, F. H. (2002) Planetesimal Formation by Gravitational Instability, Astrophys. J. 580, 494- 


Osservatorio Astronomico di Trieste — I.N.A.F. Italy 

I. Introduction 

Quasars are among the most powerful background sources for probing gas at cosmological 
distances by means of absorption-line spectroscopy. Quasar spectra show a large number of 
absorption lines, most of which are attributed to the Ly a transition of neutral hydrogen (HI) 
originating in layers of gas located in the direction of the quasar. Thanks to the cosmological 
expansion of the universe, each Ly a line falls at a different wavelength in the observer’s 
rest frame according to the redshift of the layer. In most cases, the HI lines are weak and do 
not show accompanying metal lines at the same redshift. These weak lines are believed to 
originate in the intergalactic medium, an environment highly ionized and extremely metal 
poor. Our attention here is focused on a less frequent type of quasar absorbers, character- 
ized by very strong Ly a prohles broadened by radiation damping and called damped Ly a 
absorptions (Wolfe et al. 1986). These absorptions are always accompanied by a complex of 
low-ionization metal lines at the same redshift, all together forming a Damped Ly a (DLA) 
system. There is general agreement that DLA systems originate in the interstellar medium 
(ISM) of intervening galaxies. DLAs are most easily identihed at redshift z > 2, when the 
Ly a is redshifted to the optical band, but can be detected up to z ~6, the redshift of the most 
distant quasars. This redshift interval corresponds to an interval of look-back time between 
~ 10 and ~ 12 billion years ago, according to the current values of the cosmic expansion pa- 
rameters. Therefore we can say that DLA studies probe the ISM of galaxies observed at very 
large look-back times. As a consequence, the link between DLA studies and astrobiology is 
basically the same that exists between ISM studies and astrobiology, with the advantage that 
DLA observations probe a variety of galaxies, back to the earliest epochs of their evolution. 

2. Studies of Dla Systems and Astrobiology 

The connections between DLAs studies and astrobiology can be classihed in a very 
schematic form according to the following points, which also summarize the links between 
ISM studies and astrobiology. 

1 . The ISM collects the elements produced and ejected by the stars and, in particular, 
the biogenic elements and those necessary for the formation of habitable planets; 
studies of DLAs can be used to measure the abundances of these elements during 
the early epochs of galactic evolution. 


J. Seckbach et al. (eds.), Life in the Universe, 169 - 172 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. The interstellar dust is an important component of the ISM, a basic ingredient in 
planet formation, according to planetesimal accretion models, and a catalyst of 
molecular formation; studies of DLAs can be used to probe the early build-up of 
dust in galaxies. 

3. The ISM is the site where the first formation of organic molecules occur in the 
course of galactic evolution; DLAs can be used to investigate the early interstellar 
chemistry and trace the presence of complex organic material at different cosmic 

4. The ISM probes the physical conditions of the environments where the stars and 
their planetary systems, if any, are embedded; DLAs can be used to investigate the 
habitability of these environments during the early stages of galactic evolution. 

For each of these four points we now give a concrete example, in order to show that 
DLA studies can offer unique results relevant to the field of astrobiology. 


As a first example we consider the early build-up of nitrogen. Measurements of nitrogen 
abundances in DLAs (Fig. 1, left panel) are particularly important for testing the early 
chemical evolution of galaxies. The abundances of nitrogen in DLAs are the lowest measured 
so far in any astrophysical site, with values as low as ~10“^ ^ the solar N/H number ratio 
(Centurion et al. 2003). Also the relative abundances are low; as an example, the N/Si 
ratio is ~10“' ^ the corresponding solar value. This severe deficit of an important biogenic 
element may pose a real problem for building up pre-biotic material during the earliest stages 
of galactic evolution. For instance, it is hard to imagine how a nitrogen-rich atmosphere, 
favourable to the formation of aminoacids, could be created in these conditions. 

Also other elements in DLAs have a low abundance, but they do not attain the extremely 
low values of nitrogen. For instance, the silicon abundance can be as low as ~10“^ ^ the 
solar Si/H ratio (Fig. 1, central panel). Quite interestingly, while the absolute abundances 





Figure 1. Element abundances in DLAs plotted versus look-back time (billion years ago). Abundances are 
given by number on a logarithmic scale; the zero point represents the Solar System value (dotted line). Most 
data are compiled from the literature. Also shown are the look-back time of the Big Bang (solid line) and of 
the Solar System formation (dashed line). 


(relative to H) are below solar, the relative abundances are roughly solar in many cases, 
with the remarkable exception of nitrogen noted above. For instance, the Si/Fe ratio is 
approximately solar in DLAs (Fig. 1, right panel) when depletion effects are accounted for 
(Vladilo 2002). The rapid convergence in early cosmic epochs of relative abundances to 
present-day solar values may be considered an example of convergent evolution at cosmic 
level (see Chela-Flores, these Proceedings). 


The relative abundances of volatile and refractory elements in DLAs can be used to derive 
the fraction of metals in dust form (Vladilo 2002). This fraction is expected to be roughly 
constant with metallicity because the dust is expected to track the metals in the course 
of chemical evolution. Instead, recent studies indicate that in DLAs the dust fraction (or 
depletion) is correlated with the metallicity (Ledoux et al. 2003, Vladilo 2003). This implies 
that DLA galaxies have a severe deficit of dust in the earliest stages of evolution. This 
deficit may pose a serious problem in planet formation, according to planetesimal accretion 
models. In a separate contribution to these Proceedings, I propose that planet formation in 
DLA galaxies may be inhibited when the dust fraction of iron is below ~50%, i.e. when 
the metallicity is below ~10“''^ the solar value. This would imply that planets are rare in 
DLAs at redshift z > 2. 


Molecular hydrogen is detected in a small number of DLAs; even in these cases the molecular 
fraction is rather low, with typical values between ~10”‘^ and ~10“® (Ledoux et al. 2003). 
Since H 2 is the starting point of the interstellar chemical reaction network, the general lack 
of H 2 suggests that the formation of organic molecules was inhibited atz > 2, i.e. interstellar 
organic molecules were not present until ~10 Gyr ago, at least in DLA galaxies. On the 
other hand, the first detection of the extinction bump at 2175 A at high redshift (Motta 
et al. 2002) provides an indication that complex organic material was already in place not 
much later. The 2175 A bump is a well known emission feature of the interstellar extinction 
curve, seen in the Milky Way galaxy and other nearby galaxies. The identification of the 
carrier responsible for this feature is controversial. However, there is little doubt that it is 
related to the presence of complex, carbon-bearing material. The detection of the bump at 
redshift z = 0.83 represents the most distant record of this feature so far, and indicates that 
complex, carbon-rich interstellar material was already in place ~7 Gyr ago. 


Quasar absorption data indicate that the intergalactic radiation field at high redshift is 
dominated by the continuum emitted by quasars themselves. The integrated emission of 
quasars is characterized by a hard ionizing continuum and one may wonder if this can affect 
the physical conditions of high redshift galaxies. A recent study of neutral argon in DLA 
systems suggests that this may be the case (Vladilo et al. 2003). The abundance of argon 
is significantly lower than that of other a-capture elements observed in DLAs and detailed 
computations indicates that this is an effect of ionization rather than of nucleo-synthetic 


evolution. The analysis indicates that about 12 Gyr ago the ionizing continuum in DLAs 
started to be dominated by the integrated radiation of quasars. The quasar-dominated era 
must have lasted for at least two billion years. Such a hard ionizing radiation might have 
been hostile to the formation of habitable environments; on the other hand, it might have 
triggered chemical evolution in the interstellar gas. 

3. Conclusions 

Studies of DLA systems provide unique information on the early build-up of biogenic 
elements, dust and molecules and on the existence of habitable zones in the early universe. 
Some of the results mentioned above are examples of convergence at cosmic level of the 
type discussed by Chela-Flores in these Proceedings. For instance, the approximately solar 
values of Si/Fe ratios in DLAs, already attained at early cosmic epochs; or the presence of 
the 2175 A extinction bump in a galaxy observed at a look-back time of 7 Gyr ago. On the 
other hand, other results can be used to set temporal limits to the existence of habitable zones 
in the universe. For instance, the severe deficit of nitrogen, dust and molecules in DLAs 
suggests that habitable zones are unlikely to have been formed earlier than 10 Gyr ago, at 
least in DLA galaxies. By adding the age of the earth to this limit, we obtain an estimate 
of 5.5 Gyr ago for the formation of the oldest intelligent civilization of terrestrial type. 
However, care must be taken in generalizing the DLA results to all types of galaxies since 
the exact nature of DLA galaxies is still under debate (e.g., see Calura et al. 2003). Future 
studies of quasar absorbers in different spectral bands will be able to set more stringent time 
limits and, hopefully, establish unexpected links with other topics of interest in astrobiology. 

4. References 

Calura, F, Matteucci, R, and Vladilo, G. (2003) Chemical evolution and nature of damped Lyman a systems, 
Mon.Not.Roy.Astron.Soc., 340, 59-72. 

Centurion, M., Molaro, R, Vladilo, G., Peroux, C., Levshakov, S. A., and D’Odorico, V. (2003) Early stages 
of nitrogen enrichment in galaxies: Clues from measurements in damped Lyman alpha systems, Astron. 
Astrophys. 403, 55-72. 

Ledoux, C., Petitjean, P, and Srianand, R. (2003) The VLT-UVES survey for molecular hydrogen in high-redshift 
damped Lyman-alpha systems, Mon.Not.Roy.Astron.Soc., in press (astro-ph/0302582). 

Motta,V., Mediavilla, E., Munoz, J.A., Falco, E., Kochanek, C.S., Arribas, S., Garcia-Lorenzo, B., Oscoz, A., and 
Serra-Ricart, M. (2002) Detection of the 2175A Extinction Feature at z = 0.83, Astrophys. J., 574, 719-725. 

Vladilo, G. (2002) Chemical abundances of damped Ly alpha systems: A new method for estimating dust depletion 
effects, Astrophys. 391, 407-415. 

Vladilo, G. (2003) Evolution of the dust content of Damped Ly a systems, in Astrophysics of Dust, Estes Park, 
Colorado, May 26-30, 2003 (poster presentation). 

Vladilo, G., Centurion, M., D’Odorico, V, and Peroux, C. (2003) Ar I as a tracer of ionization evolution, Astron. 
Astrophys. 402, 487^97. 

Wolfe, A. M., Turnshek, D. A., Smith, H. E., and Cohen, R. D. (1986) Damped Lyman-alpha absorption by disk 
galaxies with large redshifts. I — The Lick survey, Astrophys. J. SuppL, 61, 249-304. 



Depto. de Astronomia, P. Univ. Catolica, Casilla 306, Santiago 22, Chile 

I. Introduction 

Our civilization consumes more and more energy as it progresses. Consider that the total 
ouput from the Sun is about 4 x 10^® W, of which the illuminated Earth intercepts a small 
fraction (10“^). With our accelerated energy consumption rate, we would soon use that 
whole illuminated Earth energy. Given the cosmic timescale (see G. V. Coyne in this pro- 
ceedings), there is plenty of room for other civilizations to have been born well before ours. 
These more advanced civilizations would require unthinkable amounts of energy. Ereeman 
Dyson (1960) proposed that advanced civilizations would have the means to use all the 
energy of their parent stars by building A.U. size shells around them. Using the laws of 
thermodynamics he predicted how these “Dyson spheres” could be observed, even without 
knowing the nature of these objects. Whole or partial Dyson spheres would dim the original 
stellar light, and radiate in the IR (at about 10 p.m). 

In this paper we only address the question; Can we find candidate Dyson spheres in the 
Milky Way? We do not try to answer other questions like: Will an advanced civilization 
build a Dyson sphere?; How can a Dyson sphere be built?; Why would they build a Dyson 
sphere? How stable would it be? etc. However, most of which follows is also valid for partial 
Dyson spheres, Niven’s rings, or similar configurations. We will assume that Dyson spheres 
are rare, and that therefore one has to search through thousands of stars. Prime fields to 
monitor large numbers of stars are the disk of the Galaxy in the solar neighborhood, and 
the dense regions of the Galactic bulge. 

2. Searching for Dyson Spheres in Our Galaxy 

The main-sequence stars of the solar neighborhood can be observed with great detail and 
exquisite sensitivity. The problems are that there are relatively few stars available, and that 
they are spread all over the sky. The most systematic searches for late-type main sequence 
stars that are too faint for their spectral types, and that have IR excess have been carried out 
by Jugaku and Nishimura (1997, 2000). They used the mid-IR data from IRAS in combi- 
nation with near-IR photometry with 1.5 m class telescopes. They obtained photometry for 
180 E-G-K main sequence stars within 25 pc of the Sun, using the K-[12 mm] index to 
search for Dyson spheres. If the waste heat of the Dyson sphere is 1% of the radiation energy 


J. Seckbach et al. (eds.), Life in the Universe, 173 - 176 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. 2MASS face-on view of the inner 90 x 30 sqdeg of the Milky Way. The dashed lines limit the MSX 
observations of the Milky Way disk, and the insert shows the MACHO fields, including the fields F301, F303, 
F121 and FI 18 studied here (full squares from left to right). 

of the star, they expected a color excess > 1 mag. These searches have been unsuccessful 
so far (Jugaku and Nishimura 2000). 

The large numbers of stars present in the inner MW disk and the Galactic bulge are metal 
rich, which would favor the presence of planets, and old, which would give more chance 
to advanced civilizations to develop. We will direct our search to these fields. We should 
then search for long-lived stars, such as late-type main-sequence stars that are fainter than 
normal in the optical and near-lR, and that have infrared excesses in the mid-lR bands.There 
should be no overlap with other types of known sources in the Milky Way. But there are still 
three serious observational problems for a massive search in the inner fields of the Milky 
Way: (1) source associations may be ambiguous in crowded fields due to different spatial 
resolutions of different datasets, (2) the presence of unresolved companions can mimic IR 
excesses, and (3) variable sources can mimic IR excesses when data acquired in different 
epochs are combined. 

We will combine three large databases in order to search for Dyson Spheres in the 
inner Milky Way: the MACHO database, the 2MASS database, and the MSX database. 
The Two Micron All Sky Survey (2MASS) covered the whole sky in the near-lR bands. 
The 2MASS database is public at , containing accurate JHK 
single epoch photometry down to K = 14—15 depending on crowding. The Midcourse 
Space Experiment (MSX) database contains single epoch mid IR photometry of sources 
throughout the whole Galactic plane (Cohen et al. 2000). The calibrated MSX photometry 
is also public at . Of the six MSX bands, we will use the A-band 


TABLE 1. Numbers of Optical and IR Sources in the MACHO Fields 















6.4e -1- 5 

4.1e -1- 4 








5.9e -1- 5 

2.0e -1- 4 








5.6e -1- 5 

2.6e -1- 4 












Figure 2. 2MASS infrared color-magnitude diagrams for three different fields. The MSX IR excess sources 
are plotted as full circles, and the MACHO constant stars as black dots. 

at 8 |JLm, which is the most sensitive one, reaching 10 times deeper than IRAS. The main 
problem with this data is the poor spatial resolution. Even though it is still better than IRAS, 
the 3" to 8" resolution can lead to mismatches in the crowded bulge fields The MACHO 
bulge database contains multi-epoch optical photometry about 50 million stars in 96 bulge 
fields each of 0.5 square degree. These stars were observed for several seasons from 1993 
to 1999, and a typical light curve contains more than 1000 points. The MACHO data are 
calibrated into the standard V and R photometric system (Alcock et al. 1999), and are 
publicly available at: . We have started our search by 
looking at 2 inner bulge MACHO fields and 2 inner disk MACHO fields of the Milky 
Way. The locations of the four fields are shown in Figure 1. Table 1 lists their positions 
in equatorial and Galactic coordinates, along with the total number of sources found in 
the MACHO, 2MASS and MSX databases. They contain in total about 300 MSX sources, 
about 10^ 2MASS JHK sources, of which about 3000 are variable stars, and about 2 x 10® 
MACHO sources. 

The stellar positions of the MACHO and 2MASS data match to better than 1", while we 
consider matches within 1 " for the MSX sources. An important potential bias is that when 
more than one source is present within this matching radius, we chose the brightest optical 
source as the counterpart of the IR source. After the match is done, we search for stars that 
are > 1 mag fainter in VRJHK that lie in the disk main sequence, that have normal VRJHK 
colors, and that have > 1 mag excess at 8 pim. Another limitation is that the MSX data is not 
deep enough. Typical Solar-type stars have absolute A-band magnitudes of about 3 (Cohen 


et al. 2000). For the MSX limiting magnitude of A = 7.5, only nearby main sequence stars 
(within about 100 pc) would be detected, and main sequence stars with A-band excess 
would be detected only out to about 500 pc. 

3. Summary 

We have matched optical sources of the MACHO database with the near-IR 2MASS and 
the mid-IR MSX sources in the inner Milky Way. Figure 2 shows the IR color-magnitude 
diagrams of the four fields, with the MSX sources plotted as squares. We have identified the 
variable stars and the stars with IR excess, finding about 300 stars with >1 mag excess at 
8 |JLm, which are mostly long period variables in the bulge, with dusty circumstellar shells. 
We have not found any candidate Dyson sphere. 

However, there are other astrophysically interesting results. For example, large differ- 
ences are found between the fields. There are more variables and more giants in the bulge 
fields FI 18, F121 than in the disk fields F301, F303. There are also more IR sources in the 
bulge fields than in the disk fields. These differences indicate the presence of population 
gradients. We also see neatly the variable star sequence corresponding to first ascent giants. 
These are semiregular variables in the inner bulge and disk of the Milky Way studied by 
Minniti et al. (1998). 

In the future, the aim is to examine several 10® stars, in order to obtain limits to the 
number of Dyson spheres in our Galaxy. We are using public databases. Mining of such large 
databases is specially suited for searches like this, and the availability of the Astro-physical 
Virtual Observatory would be important for these searches. 

Even though at first sight searching for Dyson spheres may seem far-fetched, if we are 
seriously contemplating questions like the existence of life in the Universe or the number 
of advanced civilizations in the Milky Way, we must consider all possibilities. 

4. References 

Alcock, C., Allsman, R., Alves, D., Axelrod, T., Becker, A., Bennett, D., Cook, K., Freeman, K. C., Griest, 
K., Marshall, S.L., Minniti, D., Peterson. B., Pratt, M., Quinn, R, Rodgers, A., Stubbs, C., Sutherland, W., 
Tomaney, A., Vandehei, and T., Welch, D. (1999) Calibration of the MACHO Photometric Database, PASP, 
111 , 1539. 

Cohen, M., Hammersley, P. L., Egan, M. P. (2000) Radiometric Validation of the Micourse Space Experiment, 
The Astrophysical Journal, 120 , 3362. 

Dyson, F. (1960) Search for Artificial Stellar Sources of Infrared Radiation, Science, 131 , 1967. 

Jugaku, J., and Nishimura, S. (1997) A Search for Dyson Spheres Around Late Type Stars in the Solar Neighbor- 
hood, in Astronomical and Biochemical Origins, and the Search for Life in the Universe, lAU Coll. No. 161 , 
(Editrice Compositori: Bologna), p. 707. 

Jugaku, J., and Nishimura, S. (2000) A Search for Dyson Spheres Around Late Type Stars in the Solar Neighbor- 
hood, in A New Era in Bioastronomy, G. Lemarchant and K. Mitch (eds.), ASP Conf. Series 213 (ASP: San 
Francisco), p. 581. 

Minniti, D., Alcock, C., Allsman, R., Alves, D., Axelrod, T, Becker, A., Bennett, D., Cook, K., Freeman, K., Griest, 
K., Marshall, S. L., Peterson. B., Pratt, M., Quinn, P, Rodgers, A., Stubbs, C., Sutherland, W, Tomaney, A., 
Vandehei, T., and Welch, D. (1998) Pulsating Variable Stars in the MACHO Bulge Database: The Semiregular 
Variables, in: Pulsating Stars: Recent Developments in Theory and Observations (University Academy Press: 
Tokio), p. 5 (astro-ph/97 12048). 

Life Inhibitors or Catalysts? 


INAF-Trieste Astronomical Observatory, Loc. Basovizza n. 302, 34012 
Trieste, Italy and Department of Physics, Trieste University, Trieste, Italy 

Abstract. Today the Sun exhibits a stable radiation output, which is expected to endure on 
a long time scale and characterizes the Space Climate (SpC). On a short time scale the solar 
activity perturbs the heliosphere by originating radiation outbursts, highly energetic particles 
and plasmoids, which characterize the Space Weather (SpW). A similar phenomenology can 
occur in solar-like stars and affect the exoplanetary environments. In this work we speculate on 
the possible mutual role of SpW and SpC on life birth and evolution, stressing the inadequacy 
of the basic concept of Habitability Zone and the relevance of SpW and SpC to life-genicity 
and life-sustainability. 

1. Introduction 

The Sun is a yellow dwarf star (G2V class) presently in a stable Hydrogen burning phase, 
variable on a second order scale and with low magneticity, which drives the solar activity 
cycle. Solar activity is a complex of phenomena, that are variable on spatial, time and energy 
scales and occur in the photosphere (sunspots), chromosphere (flares), corona (Coronal Mass 
Ejections, CME) and solar wind (fast plasma streams), as heating, particle acceleration, 
waves and shocks, emission of radiation, plasmoid formation, triggered by fluid motions 
and interacting magnetic fields at different spatial scales. Short- and long-term evolution of 
solar irradiance and activity has been determining the energy input to the planets and the 
physical state of the planetary environments. Such an evolution played a key role in favoring 
the birth of life on the Earth, an attitude of the solar-planetary environment which we define 
life-genicity, and has been playing a fundamental role in keeping favorable conditions to the 
preservation and evolution of life, which we define life-sustainability . By extending these 
concepts to exoplanetary systems around solar-like stars, we elaborate on the need to extend 
the concepts of Habitability Zone (HZ) by explicitly incorporating the related Stellar Space 

2. Space Meteorology of the Stellar-Planetary Environment 

An unperturbed stellar-planetary environment is a complex physical system composed of 
coupled physical subsystems such as: a) the Interstellar Wind (ISW), a diluted magne- 
tized plasma accelerated by neighboring stars which feeds the Interstellar Medium (ISM), 


J. Seckbach et al. (eds.), Life in the Universe, 177 - 180 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


permeates the local galactic environment and vehiculates the interstellar magnetic field; b) 
the central star, a magnetized plasma in an organized state; c) the Stellar Wind (SW), a mag- 
netized plasma accelerated by the central star that, together with dust particles, originates 
the Interplanetary Medium (IPM), permeates the planetary environment and vehiculates the 
Interplanetary Magnetic Field (IPMF); d) planet(s), gaseous or condensed mass(es) of orga- 
nized matter with or without a Planetary Magnetic Field (PMF). The ISW flows externally 
to the IPMF and confines the SW in a region called stellarsphere, compressed towards the 
ISW source and elongated in the opposite direction. Analogously the SW acts on the PMF 
and originates the planetary magnetosphere(s). Such physical subsystems are characterized 
by different physical conditions defined by the state of the neighboring stars, the central 
star and the dynamical history of the planetary system. Various outer perturbations can 
affect the stellar-planetary environment (Figure 1), e.g. cosmic rays, high energy particles 
accelerated in violent astrophysical processes, shocks in the ISW and radiation outbursts as 
observed in supernovae explosions. Inner perturbations come from the central star, which 
can be characterized by a certain level of magnetic activity as starspots. Stellar flares, sig- 
natures of impulsive magnetic energy release, determine radiation outbursts in the y , X, 
Extreme Ultra Violet (EUV) and UV domains. Large mass ejections from the stellar corona 
(plasma clouds) can be accelerated towards the planet(s) and originate stellar wind shocks. 
Stellar cosmic rays are generated by the star in energetic activity phenomena. Planetary 
debris (meteoroids, comets and asteroids) hit the planet(s), whose size and trajectories are 
defined by the planetary population diversity and orbital dynamics. Similarly to the solar 
case. Stellar Space Meteorology (SSpM) is aimed to observing and modeling the state of 
the stellarsphere and its perturbations on a short {Stellar Space Weather, SSpW) to a long 
time scale {Stellar Space Climatology, SSpC). 

3. Stellar Space Meteorology and Planetary Response Drivers 

The drivers ofSSpM (Eigure 1) are intrinsic to: a) the local galactic neighborhood (LGN); 
b) the central star typology; c) the planetary system environment. Specifically, the LGN star 


population determines: - the flow and energy spectrum of galactic cosmic rays; - the occur- 
rence frequency and morphology of ISW shocks; - the occurrence frequency and intensity of 
interstellar radiation outbursts in the 7 , UV and EUV bands, and of stellar cosmic rays flow. 
Similarly, the central star is characterized by: - its evolutionary state and global irradiance 
level; - magneticity, which determines the surface activity level on a short time scale; - 
variability, which biases the long-term irradiance variations; - wind, which modulates the 
galactic and stellar cosmic rays, and sweeps the planetary environments. Stellar mass ejec- 
tions, wind shocks and radiation outbursts are dependent on evolutionary stage, magneticity 
and activity level. In fact, the main activity features observed in solar-like stars on a non- 
systematic basis are: - very large photospheric starspots; - high energy stellar flares; - huge 
stellar coronal mass ejections; - stellar activity cycles. As such stellar features can occur 
at scales order of magnitudes larger than the solar homologous ones (Schrijver and Zwaan, 
2000 ), the stellar activity level and the variety of stellar activity phenomena represent fun- 
damental features to consider when characterizing stellar-planetary environments for life 
origination and preservation. The planetary system environment is furthermore populated by 
a variety of planetary debris. The planetary response drivers to SSpM are respectively mass, 
radius, density, orbital dynamics, surface morphology, atmosphere (that can filter and modu- 
late the SpM radiation effects and determines the thermodynamics driven by the stellar radia- 
tion) and magnetosphere (key factor in shielding and modulating the SpW particular effects). 

4. Relevance of Stellar Space Meteorology to Habitability Zones 

At a galactic spatial scale the Galactic Habitability Zone (GHC) (Gonzalez etal., 2001) is de- 
fined as an environment in a galaxy favorable to life, populated by suitable neighboring stars 
(e.g. no nearby supernovae), solar-like stars (characterized by a “normal”, non-cataclysmic 
evolution), and a suitable interstellar medium (with organics). At a planetary spatial scale 
the Habitability Zone (HZ) (Kasting, 1996) is defined as a set of stable planetary orbits to 
allow for liquid water to exist on a planet. This requirement is a necessary condition, but is it 
also a sufficient condition for life-genicity? The Continuous HZ (Kasting, 1996) is defined 
in terms of a stellar environment favorable to life in time. Is this condition sufficient for 

Let us assume a possible scenario for the origin of life (e.g. Baross, 2002): a) a pri- 
mordial soup is originated; b) the environment is fed with energy and some unidenti- 
fied synergetic mechanism(s) operates (the “twilight zone”); c) an RNA world is formed; 
d) RNA and protein biosynthesis occurs; e) the environment is progressively populated by 
cells with DNA, RNA and proteins. The concept of life-genicity implies stellar-planetary 
conditions favorable to originate life, which means a central star with “suitable ” stellar 
activity (respectively “moderate” irradiance, wind, radiation outbursts, particle emissions, 
coronal mass ejections) and a “suitable” planetary configuration (adequate atmosphere 
and magnetosphere, moderate debris bombardment). The role ofSSpM in life-genicity has 
to be considered in terms of both SSpC (presently the solar irradiance variations are lower 
than 0 . 1 % but new solar models imply an initial irradiance higher than the present one) 
(Tehrany et al., 2002 and references therein), which defines the peak energy input to the 
planet, and SSpW (stellar activity modulates and planetary magnetosphere shield cosmic 
rays; planetary atmosphere modulates radiation and particles at sea level), which determines 
the peak biological suitability of the planetary environment. How much relevant are SSpC 


and SSpW to the “Twilight Zone”? How to quantify the attributes “suitable”, “moderate” 
and “adequate”? How to define the “peak biological suitability”? When does SSpM act as 
life catalyst and when like life inhibitor! The existence of life can be schematically described 
respectively in terms of: a) existence o/ cells with DNA, RNA and proteins; b) evolution 
to complex life forms; c) evolution o/ complex life forms; d) persistence o/ complex life 
forms. The concept of life-sustainability involves stellar-planetary conditions favorable to 
preserve life, i.e. “suitable” stellar activity and a “suitable” planetary configuration (ade- 
quate biosphere and magnetosphere, moderate debris bombardment). The role ofSSpM 'm 
life-sustainability is determined by the SSpC (long-term evolution of stellar irradiance and 
existence and intensity of an activity cycle), which modulates in time the planetary energy 
input, and by the SSpW (cosmic rays modulation and shielding, modulation of radiation and 
particles at sea level), which determines the long-term biological harshness of the plan- 
etary environment. How much relevant are SSpC and SSpW to the “long-term biological 
harshness”? How to define the “biological harshness”? 

5. Conclusions 

New environmental aspects are worthwhile investigating in the framework of Stellar Astro- 
physics, Exoplanetology and Astrobiology. Solar Space Weather and Space Climate have 
been playing a fundamental role in life-genicity and life-sustainability on the Earth and acted 
as life catalysts. Hence the definitions of Galactic and (Continuous) Habitability Zones must 
be extended to account for Stellar Space Meteorology, based on a refinement of Solar SpM, 
as Stellar SpM is beyond the present instrumental capabilities. A detailed analysis in the 
framework of Astrobiology can provide new information to quantify the relevant biological 
characteristics of a planetary environment such as life-genicity and peak biological suit- 
ability as well as life- sustainability and long-term biological harshness. This will help in 
understanding when SSpM acts as life catalyst or inhibitor in exoplanetary environments, 
unobservable at a high level of detail. 

6. References 

Baross, J.A. (2002) The Definition of Life and the Origin of Life on Earth, Bull. Am. Astron. Soc. 34, p. 1213. 
Gonzalez, G., Brownlee, D. and Ward, P. (2001) The Galactic Habitable Zone: Galactic Chemical Evolution, 
Icarus 152, 1, pp. 185-200. 

Kasting, J.F. (1996) Habitability of Planets, Astrobiology Workshop: Leadership in Astrobiology, pp. AlO-Al 1. 
Schrijver, C.J. and Zwaan, C. (2000) Solar and Stellar Magnetic Activity, Cambridge Astrophysics Series 34, 
Cambridge University Press, Cambridge, UK. 

Tehrany, M.G., Lammer, H., Selsis, F., Ribas, G., Guinan, E.F, Hanslmeier, A. (2002) The particle and radiation 
environment of the early Sun, In: A. Wilson (ed.) Proc. Solar variability: from core to outer frontiers, ESA 
SP-506, l,pp. 209-212. 

VII. Planetary Exploration in our Solar 
System: The Interstellar Medium, 
Micro-Meteorites and Comets 



Dept. Physical Chemistry, University of Bremen 
Fachbereich 2, Leobener Strafe, 28359 Bremen, Germany 

Abstract. In dense interstellar clouds dust particles accrete ice mantles. As seen in infrared 
(IR) observations, this ice layer consists mainly of water ice, but also of carbon and nitrogen 
containing molecules. We deposited a gas mixture consisting of H 2 O, CO 2 , CO, CH 3 OH, and 
NH 3 onto an aluminium surface at 12 K under high vacuum, 10“^ mbar. During deposition 
the molecules were subjected to ultraviolet radiation with main intensity at Lyman-a. After 
warm-up, the refractory material was extracted from the aluminium block, hydrolysed for 
24 h at 1 10 °C with 6 M HCl, derivatized and finally analysed by enantioselective gas chro- 
matography coupled to a mass spectrometer. We were able to identify 16 amino acids in the 
room temperature products of irradiation. The results were confirmed by parallel experiments 
using *^C-labelled ices in order to exclude contamination. A first ‘group’ of the identified 
amino acids was suggested to serve as the precursors of peptides and proteins. A second 
‘group’ namely the diamino carboxylic acids is assumed to contribute to the development of 
the first genetic material, the peptide nucleic acid PNA. Beside the two groups of amino acids, 
N-heterocyclic organic molecules were identified that resemble the molecular building block 
of biological cofactors. The obtained results support the assumption that the photochemical 
products could be preserved in interstellar objects, and in term be delivered to the Earth during 
the heavy bombardment which ended about 3.8 Gyr ago, where they triggered the appearance of 

I. Introduction 

In order to understand availability and distribution of molecular building blocks of biolog- 
ical systems during defined phases of the Chemical Evolution we studied and simulated 
interstellar/circumstellar processes in the laboratory. Based on the knowledge of inten- 
sity, energy, and polarization of interstellar/circumstellar electromagnetic radiation (Bailey 
et al., 1998), and on the occurrence and abundance of volatile compounds in interstellar 
clouds/circumstellar disks like H 2 O, CO 2 , CO, CH 3 OH, and NH 3 interstellar/circumstellar 
photochemical processes were simulated in the laboratory. Scientific objective of these ex- 
periments was to synthesize interstellar ices under most realistic conditions in order to test 
the enantioselective GC-MS instrumentation developed for the Rosetta-Lander cometary 
sampling and composition experiment COSAC at the Max-Planck-Institut fiir Aeronomie 
in Katlenburg-Lindau, Germany. The experiments were not optimised in order to identify 
any organic compounds under simulated interstellar/circumstellar conditions. 


J. Seckbach et al. (eds.), Life in the Universe, 183 - 186 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Simulation of Interstellar/Circumstellar Ices 

At the Raymond and Beverly Sackler Laboratory for Astrophysics at Leiden Observatory, 
the Netherlands, J. Mayo Greenberg’s (f ) student G. M. Munoz Caro deposited the volatile 
compounds H2O, CO2, CO, CH3OH, and NH3 (molecular composition 2:1: 1:1:1) onto an 
aluminium block at a representative temperature of 1 2 K during UV-irradiation in a specially 
developed space simulation vacuum chamber. After 24 h irradiation a residue of yellowish 
color remained on the aluminum block (Munoz Caro et ai, 2001). After a stepwise warm- 
up procedure and the vacuum venting process this residue was kept under inert gas until 

3. Enantioselective GC-MS Analysis of Amino Acids 

At the Centre de Biophysique Moleculaire in Orleans, France, the irradiated samples of 
interstellar/circumstellar ice analogues were analysed in the group of Andre Brack and 
Bernard Barbier. Therefore, a new and sensitive analytical procedure was developed that 
consists of the sample’s extraction with 100 |xL water, the 24 h hydrolysis at 1 10 °C with 
6 M HCl, the chemical transformation of amino acids into the N-ethoxycarbonyl ethyl ester 
derivatives (Abe et al., 1996), and the enantioselective capillary GC-MS analysis (Huang 
et ai, 1993) using the Agilent 6890/5973 GC-MSD system. 

4. Amino Acid Identification in Simulated Interstellar/Circumstellar Ices 

The application of the new analytical procedure allowed us the identification of 16 amino 
acids in the simulated interstellar/circumstellar ice samples (Munoz Caro et ai, 2002). The 
gas chromatogram is given in Figure 1 . 

Among the 16 amino acids are L-Ala, Gly, L-Val, L-Pro, L-Asp and L-Ser, i.e. six 
ot-amino acids being the molecular constituents of proteins. The results suggest, that the 
structures of these a-amino acids can be synthesized under interstellar/circumstellar con- 
ditions and be delivered via asteroids, comets and interplanetary dust particles to the early 
Earth, where they might have triggered the appearance of live. 

Beside the proteinacous a-amino acids, six diamino acids were identified in fhe inter- 
sfellar/circumstellar ice analogues. These sfructures are the molecular constituents of the 
backbone of the peptide nucleic acid PNA (Egholm et ai, 1992). PNA is considered to be 
a potential early genetic material on Earth, where it might have preceded RNA and DNA 
(Nielsen, 1993 and Nelson et al., 2000). PNA hybridizes to complementary oligonucleotides 
obeying the Watson-Crick hydrogen-bonding rules (Egholm etal., 1993). Its backbone con- 
sists of diamino acids linked via peptide bonds. The nucleic bases can be attached with the 
help of various molecular spacer groups to the PNA backbone. 

As expected, the identified amino acids showed racemic occurrence. In fufure exper- 
imenfs, the applied light source that emitted unpolarized light will be substituted by a 
circularly polarized synchrotron beam in the Trench synchrotron facility LURE, Paris. 
Circularly polarized electromagnetic radiation has been identified in fhe Orion sfar for- 
mation region by J. Bailey and his group (1998). With these experiment we try to mimic 


Time (min) 

Figure 1. Amino acids identified in interstellar/circumstellar ice analogues by enantioselective gas chromatog- 
raphy. Varian-Chrompack Chirasil-L-Val capillary column 12 m x 0.25 mm inner diameter, film thickness 
0.12 p,m, splitless injection, 1.5 mL/min constant flow of He carrier gas, oven temperature programmed for 
3 min at 70 °C, 5 °C/min, and 17.5 min at 180 °C, detection of total ion current TIC. DAP, diaminopentanoic 
acid; DAH, diaminohexanoic acid. 

interstellar/circumstellar conditions even more realistically and to introduce an enantiomeric 
excess into the produced amino acids by absolute asymmetric photochemistry (Griesbeck 
and Meierhenrich, 2002). 

5. Discussion 

Amino acid structures, the molecular building blocks of proteins and diamino acid struc- 
tures, the molecular constituents of the PNA backbone, were identified in simulated inter- 
stellar/circumstellar ice analogues. The results suggest that both early proteins and early 
genetic material was synthesized from building blocks that had been delivered from inter- 
stellar/circumstellar space to the early Earth. Organic molecules like amino acids might 
survive an impact onto the early Earth (Greenberg etal, 1994) as the results from the Stone 
artificial meteorite experiments indicate (Brack, 2003) The organic molecules might have 
played an important role on the appearance of primitive life on Earth. The identification 
of amino acids in interstellar ice analogues is suggested to be linked with the prebiotic 
development of proteins, genetic material and biological cofactors on Earth. The COSAC 
experiment with its enantioselective GC-MS instrumentation (Meierhenrich et al., 1999; 
Thiemann and Meierhenrich, 2001) is envisaged to verify the analyses of organic molecules 
in cometary ices in situ and in continuation to elucidate possible origins of life. 


6. Acknowledgements 

I would like to thank Wolfram H.-P. Thiemann, Dept. Physical Chemistry at the University 
of Bremen, Germany, most sincerely for uncountable enlightening discussions based on his 
experience in the field and his tremendous support for the studies yielding to this work. He in- 
troduced me into the intriguing field of chirality. My thanks go to Helmut Rosenbauer for his 
support and for his fascinating basic work on the COS AC experiment. Intensive experimen- 
tal cooperations were performed with J. Mayo Greenberg (f ) at the Raymond and Beverly 
Sackler Laboratory for Astrophysics at the Leiden Observatory in the Netherlands, and his 
group composed of Guillermo M. Munoz Caro, Willem A. Schutte, and Almudena Arcones 
Segovia. I particularly acknowledge the pleasant cooperation with J. Mayo Greenberg’s 
Ph.D. student Guillermo M. Munoz Caro and his carefully performed experiments on the 
simulation of interstellar ices with isotopically labelled reactants. This work is dedicated to 
the memory of J. Mayo Greenberg, who died on 29 November 2001 . 1 particularly acknowl- 
edge the generous support from the Centre de Biophysique Moleculaire C.B.M. (CNRS) in 
Orleans, France, and the prominent laboratory of Andre Brack and Bernard Barbier. I am 
very grateful for my present position at the University of Bremen, GC-MS instrumentation 
and students founded by the Deutsche Forschungsgemeinschaft DFG, Bonn, Germany. 

7. References 

Abe, I., Fujimoto, N., Nishiyama, T., Terada, K. and Nakahara, T. (1996) Rapid analysis of amino acid enantiomers 
by chiral-phase capillary gas chromatography, J. Chromatogr. A 722 , pp. 221-227. 

Bailey, J.,Chrysostomou, A., Hough, J.H., Gledhill, T.M., McCall, A., Clark, S., Menard, F. andTamura, M. (1998) 
Circular Polarization in Star-Formation Region: Implications for Biomolecular Homochirality, Science 281 , 
pp. 672-674. 

Brack, A. (2003) Search for life on Mars: The Beagle 2 Lander and the Stone Experiment, in this volume. 

Egholm, M., Burchardt, O., Nielsen, P.E. and Berg, R.H. (1992) Peptide Nucleic Acids (PNA). Oligonucleotide 
Analogues with an Achiral Peptide Backbone, J. Am. Chem. Soc. 114 , pp. 1895-1897. 

Egholm, M., Burchardt, O., Christensen, L., Behrens, C., Freier, S.M., Driver, D.A., Berg, R.H., Kim, S.K., Norden, 
B. and Nielsen, P.E. (1993) PNA hybridizes to complementary oligonucleotides obeying the Watson-Crick 
hydrogen-bonding rules. Nature 365 , pp. 566-568. 

Greenberg, J.M., Kouchi, A., Niessen, W., Irth, H., van Paradijs, J., de Groot, M. and Hermsen, W. (1994) Interstellar 
dust, chirality, comets and the origins of life: life from dead stars? J. Biol. Phys. 20 , pp. 61-70. 

Griesbeck A.G. and Meierhenrich U.J. (2002) Asymmetric Photochemistry and Photochirogenesis, Angew. Chem. 
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Huang, Z.-H., Wang, J., Gage, D.A., Watson, J.T. and Sweeley, C.C. (1993) Characterization of N-ethoxycarbonyl 
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Meierhenrich, U., Thiemann, W.H.-R, and Rosenbauer H. (1999) Molecular Parity Violation via Comets? Chirality 
11 , pp. 575-582. 

Munoz Caro, G.M., Ruiterkamp, R., Schutte, W.A., Greenberg, J.M. and Mennella, V. (2001) UV photodestruction 
of CH bonds and the evolution of the 3.4 micron feature carrier. I. The case of aliphatic and aromatic molecular 
species, Astrophys. 367 , pp. 347. 

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genetic molecule, Proc. Natl. Acad. Science 97, pp. 3868-3871. 

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and F. RAULIN 

LISA, Universites de Paris 7 et 12, UMR CNRS 7583, Universites Paris 7 
and 12, CMC, 61 Av. du Gal de Gaulle, 94010 Creteil Cedex, France 

I. Introduction 

Most of the molecules observed in the cometary environment are directly produced by 
sublimation from the nucleus, and the main fraction of the observed radicals is the result 
of the photodissociation of gaseous “parent” molecules already observed. However some 
of these species (especially CO, H 2 CO, CN. . . ) have a spatial distribution which can not 
be explained by these processes. They are produced by an unknown “extended source” in 
the coma. If one could infer the nature of the material involved in this phenomenon, this 
should allow to constraint the chemical composition of cometary grains and nucleus which 
is of prime interest for the exobiology studies. 

In this paper, we report the study of the origin of the formaldehyde (H 2 CO) and 
CN radical extended sources. The H 2 CO density profiles has been derived in comet 
IP/Halley from the Giotto NMS measurements (Meier et al, 1993). These observations 
have demonstrated that H 2 CO is not produced only by nucleus sublimation but rather by an 
“extended source”. The case of CN radicals is similar but not identical since it is a radi- 
cal, and an important fraction is produced by the photodissociation of HCN (Fray et al., 
submitted b). 

In both cases, it has been proposed that these species could be produced by the degra- 
dation of large organic molecules present on cometary grains. These compounds could be 
decomposed into gaseous molecules by UV irradiation or heating when the comet reaches 
perihelion. Polyoxymethylene [formaldehyde polymer: (-CH 2 - 0 -)n, also called POM] could 
produce gaseous H 2 CO (Meier et al., 1993) and CN radicals could be produced by the de- 
composition of hexamethylenetetramine (C 6 H 12 N 4 , also called HMT) (Bernstein et al, 
1995) and/or of HCN polymers (Huebner et al, 1989). Unfortunately the lack of quanti- 
tative data relative to the decomposition of such compounds has prevented to confirm this 
hypothesis so far. Thus, we have developed a specific experimental setup to measure the 
kinetics of the decomposition of large solid organic molecules into gaseous molecules by 
thermal or photo processes. 


J. Seckbach et al. (eds.), Life in the Universe, 187 - 190 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Experimental Setup 

The experimental setup designed for the study of photodegradation is mainly composed of a 
UV lamp and a pyrex reactor. It has been presented in details in Cottin et al. (2000). The UV 
lamp can emit at 122, 147 and 193 nm depending on the filling gas. For each wavelength, 
the UV flux is measured hy chemical actinometers and is about 10'^ photons per second. 
The photochemical reactor, in which solid molecules are deposited in order to be irradiated, 
is equipped with two vacuum stopcocks, one leading to the analysis system and another one 
to a turbomolecular pump. A vacuum, better than 10“"^ mbar, can be achieved in the reactor. 
Generally the reactor is directly connected to a FTIR spectrometer. Successive spectra can 
be collected to follow the production of gaseous molecule as a function of time. Then, 
combining the known UV flux and the kinetic measurements, we can derive the production 
quantum yields of each gaseous molecule. 

In order to study thermal degradation, we have developed two different reactors. Between 
210 and 350 K, we use a pyrex reactor equipped with a double wall, which allows the 
circulation of a thermostated fluid. For higher temperatures, up to 600 K, we use a metallic 
reactor in which a heating resistance is included. According to the temperature range of 
degradation of the studied molecule, we choose one reactor or the other. The pyrex reactor 
has been used to study the thermal degradation of POM. But, as HMT and HCN polymers 
are stable at room temperature, the study of their thermal degradation has been performed 
only at high temperature in the metallic reactor. 

3. Decomposition of H 2 CO Polymers. Application to the H 2 CO Extended Source 

The photodegradation of POM has been performed by Cottin etal. (2000) . They have shown 
that several oxygenated compounds (H 2 CO, HCOOH, CO, CO 2 and CH 3 OH) are produced 
by UV irradiation of POM at 122, 147 and 193 nm. The production quantum yield of 
H 2 CO is roughly equal to 1 up to 147 nm and decreases for longer wavelengths. By thermal 
heating, POM produces only gaseous H 2 CO. This production has been measured between 
255 and 330 K for two different types of POM coming from two different suppliers: Prolabo 
and Aldrich {Fray et al, submitted a). Our measurements are presented in Figure 1, which 

DO m 2M 3t0 nO 250 








♦ 34 



c 32 

0.0030 0.0032 0.0034 0.0036 0,0038 0.0040 

WT(K ’» 

Figure 1. Logarithim of the H2CO production rates as a fuction of the inverse of the temperature for the 
“Prolabo POM” in black and for the “Aldrich POM” in grey. 


shows the logarithm of the production (in molecules . s“') as a function of the inverse 

of the temperature. 

These measurements are well fitted hy a straight line; this shows that the production of 
gaseous formaldehyde from solid POM follows the Arrhenius law (i.e. k (T) = 

Hence, these fits allow us to determine Ea, the activation barrier and A, the frequency factor 
for both types of POM (see Figure 1). 

The value of the activation energy is quite important; it shows that the kinetics of 
gaseous H 2 CO production is highly sensitive to the temperature. The production of gaseous 
formaldehyde is different for both type of POM; at 310 K it is 1.8 times higher for the 
“Prolabo POM” than for the “Aldrich POM”. So far, the origin of this discrepancy is not 
understood but could be due to different general structure of the polymer or to different 
ending of their chains. These quantitative results on the thermal and photo degradation of 
POM have been incorporated in a model of the cometary environment to explain the H 2 CO 
extended source. 

This model of the coma (Cottin et ai, in press) allows us to fit very well the H 2 CO 
density profiles which have been obtained from Giotto NMS measurements {Meier et ai, 
1993) taking into account the production of gaseous H 2 CO by degradation of solid POM 
present on grains. New results which have been obtained taking into account these new 
measurements of the thermal degradation of POM, are presented in Fray et al. (submitted 
a). Depending on the parameters that we used for the cometary grains, the percentage of 
POM by mass needed to reproduce the observations is ranging from 1.3 to 15.5%. These 
values are in agreement with previous estimations. Thus the degradation of POM is so far 
the best quantitative explanation of the H 2 CO extended source in comets. And thereafter 
the presence of POM in cometary nucleus is highly probable. 

4. Degradation of HMT and HCN Polymers. Application to the CN Extended Sonrce 

HCN has been detected in small amount after UV irradiation of HMT at 147 nm. NH 3 and 
some heavier compounds are also produced if 0. 1 mbar of water is added during irradiation 
{Cottin et al, 2002). Nevertheless, HMT seems to be quite resistant to photolysis. Whereas 
Iwakami et al (1968) have reported the thermal decomposition of HMT by pyrolysis, we 
found that HMT sublimates when slowly heated. Thus, HMT does not seem to be a good 
candidate to explain the CN extended source. 

After UV irradiation at 122 and 147 nm of HCN polymers, we have detected HCN 
and C 2 H 2 by IR spectroscopy. And, as we show in Figure 2, by heating the sample, we 
have observed the signature of HCN, NH 3 , HNCO, CO and CO 2 at every temperature 
between 430 and 670 K. The major products are NH 3 and HCN. CO 2 does not seem to 
be a degradation product of HCN polymer and its presence in spectra is certainly due to 
instability of the purge of the FTIR spectrometer. HNCO and CO could be produced by 
reaction between degradation products with H 2 O which is trapped in HCN polymers. We are 
currently measuring the production kinetics of each product as a function of the temperature. 
Nevertheless these first results show that HCN polymers produce gaseous compounds in 
conditions relevant of the cometary grains, and thus could also be plausible parents for the 
cometary CN radicals, which cannot be directly detected in our experiments yet. Indeed, to 
date, it not clear whether HCN is directly released from the polymer, or if it is rather CN that 


im :mi i(m im* iiH i«m im m« 

M «ni 'i 

Figure 2. IR spectra of the gaseous ocmpounds produced by heating of HCN polymers at 450 K. 

is produced and promptly reacts to form HCN. Direct detection of CN radical by LIF (Laser 
Induced Fluorescence) and quantify-cation by CRDS (Cavity Ring-Down Spectroscopy) 
are planned to investigate this point. 

5. Conclusion 

To explain H2CO and CN extended source, we have studied the photo and thermal de- 
composition of POM, HMT and HCN polymers. We show that the degradation of POM 
in solid state on grains is to date the best explanation of the H2CO extended source. Thus, 
the presence of POM in cometary nucleus is highly probable. To explain the CN origin 
in cometary atmospheres, HCN polymers seem to be a better candidate than HMT. New 
experiments are planned to confirm this hypothesis. 

6. References 

Bernstein, M.P., S.A. Sandford, L.J. Allamandola, S. Chang, and M.A. Scharberg (1995) Organic Compounds 
Produced By Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol. The Astro- 
physicalJournal, 454, 327-344. 

Cottin, H., S. Bachir, F. Raulin, and M.C. Gazeau (2002) Photodegradation of HMT by VUV and its relevance for 
CN and HCN extended sources in comets. Advances in Space Research., 30(6), 1481-1488. 

Cottin, H., M.C. Gazeau, J.F. Doussin, and F. Raulin (2000) An experimental study of the photodegradation of 
polyoxymethylene at 122, 147 and 193 nm. Journal of photochemistry and photobiology A: Chemistry, 135, 

Cottin, H., M.C. Gazeau, and F. Raulin (1999) Cometary organic chemistry: a review from observations, numerical 
and experimental simulations. Planetary and Space Science, 47(8-9), 1 141-1 162. 

Cottin, H., Y. Benilan, M.C. Gazeau and F. Raulin (in press) Origin of cometary extended sources from degradation 
of refractory organics on grain: polyoxymethylene as formaldehyde parent molecule. Icarus. 

Fray, N., Y. Benilan, H. Cottin, and M.-C. Gazeau (submitted-a) New experimental results on the degradation 
of polyoxymethylene. Application to the origin of the formaldehyde extended source in comets. Journal of 
Geophysical Research Planets. 

Fray, N., Y. Benilan, H. Cottin, M.-C. Gazeau, and J. Crovisier (submitted-b) CN extended source: a review of 
observations and modelisations. Planetary and Space Science. 

Huebner, W.F., D.C. Boice, and A. Korth (1989) Halley’s polymeric organic molecules. Advances in Space 
Research, 9, 29-34. 

Iwakami, Y, M. Takazono, and T. Tsuchiya (1968) Thermal decomposition of Hexamethylene Tetramine. Bulletin 
of the Chemical Society of Japan, 41, 813-817. 

Meier, R., P. Eberhardt, D. Krankowsky, and R.R. Hodges (1993) The extended formaldehyde source in comet 
P/Halley. Astronomy and Astrophysics, 277, 677-691. 



^S.N. Bose National Center For Basic Sciences, JD — Block, Sector — III, 
Salt Lake, Kolkata 700098, India; ^Indian Astrobiology 
Network( IAN), Center For Space Physics, Chalantika 43, 

Garia Station Rd, Kolkata 700084, India; ^Maharaja Manindra Chandra 
College, Kolkata 700003, India. 

I. Introduction 

Many bio-molecules have now been observed in meteorites which showered the Earth. How- 
ever, even though about 124 organic molecules have been observed in star forming regions, 
it is doubtful if any amino acids have been detected. The problem is probably not that these 
bio-molecules are not present, but that they are of very small in abundance so that the present 
detection techniques are sufficiently sensitive. In our view, for any reaction rate, given a large 
laboratory such as a molecular cloud and a sufficient time such as about ten million years 
(the time scale of collapse) it is not unlikely that complex bio-molecules could form during 
the star formation itself. The problems lies in (a) to identify the pathways to produce these 
molecule, given that the ice chemistry and grain-chemistry are very important, (b) to use ap- 
propriate reaction rates for each pathways and finally (c) to use an appropriate hydrodynamic 
evolution of the collapse which govern the temperature and density of the collapsing matter. 

In our work we follow an unconventional route to check if the complex molecules could 
be formed or not. Instead of waiting for chemists to come up with the right pathways and 
experimentalists to come up with the right reaction rates, we assume standard pathways 
from textbooks and use reaction rates as parameters. By choice of reasonable parameters 
we conclude that simple amino acids like glycine and alanine may be produced in space and 
they may even be detectable. We think that more complex molecules, such as urea, adenine 
etc. may also form, though the abundance of adenine is even lower, and possibly may not 
be detectable in near future. This exercise does trivialize a complex part of the formation of 
life — in fact it makes the presence of bio-molecules (and therefore life) to be more generic 
than thought previously. 

2. Our Approach 

Our approach may be briefly written down as follows: (a) We collect a large number of 
chemical species which we think could be responsible for life formation, (b) We collect the 


J. Seckbach et al. (eds.), Life in the Universe, 191 - 194 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


reactions which may take place among them, and also in presence of radiations, cosmic rays 
etc. and compile the reaction rates as functions of density and temperature, (c) We define 
a model of the collapsing interstellar cloud, i.e., we pre-define the variation of the density, 
temperature and velocity of a collapsing cloud, (d) We allow the chemical reactions to take 
place at each time step during infall. We expect that part of the matter would form outflows 
and jets as in any rotating and collapsing system (such as young stellar objects, or YSOs) 
and therefore, we expect that some of the matter would be re-cycled and there will be scope 
to produce more complex molecules. 

We simplify the problem presently (a) by choosing a spherical freely falling collapse, 
(b) by ignoring the effect of the energy release on the collapsing cloud, (c) by assum- 
ing isothermal infall till the rotation becomes important and (d) by ignoring the effect 
of recycling mentioned above. Furthermore, we assume two parameter family (a, (3) of 
reaction rates mentioned in Chakrabarti and Chakrabarti (2000a). In this case, while form- 
ing a complex molecule, we assume that it is made up of successive two-body reactions 
(wherever permissible) and the two body reaction rate of the first step is a. However, as 
the molecules grow in size, the reaction rate is increased by a factor of (3. This will take 
care of the increase in reaction rates as the size grows. In future we plan to relax these 

A very important improvement of our code has been done: In Chakrabarti and 
Chakrabarti (2000ab) we used the H -f H ^ H 2 rate from UMIST database. But presently, 
we assume compute the H 2 formation on grain surfaces by a very rigorous method. Briefly, 
we separated the existence of mainly three types of grains and used the master equation and 
rate equations (Biham et al. 2001; Herbst, 1992) to compute mass fraction of H 2 as matter 
collapses. We then use this H 2 to find out the mass fractions of more complex molecules 
such as glycine, alanine, urea etc. 

The result of our computation clearly depends on the initial abundance of the chemical 
special present in the interstellar cloud. For instance, the chemical composition of the solar 
neighbourhood and that near a carbon star would be very much different and therefore the 
final product would vary. In the present analysis we use the solar neighbourhood abundance 
as the initial condition. 

3. Results 

Figs, l(a-c) show the variation of the mass fraction (along Y-axis) of complex molecules 
such as glycine, alanine, urea and adenine with the radial distance (along X-axis) drawn in 
logarithmic scale. We use a = 10~'^ in Fig. la, 10“'^ in Fig. lb and 10“'^ in Fig. Ic. We 
assume (3 = 1 in the first two-body reaction in a chain reaction, p = 4 for the two-body 
reaction second in the chain (see, Chakrabarti and Chakrabarti, 2000a), p = 9 for the next 
two body reaction in the chain and so on. 

A comparison of the mass fractions suggest that in the case of adenine, the abundance 
progressively goes down as the reaction rate is decreased. Glycine and alanine have peak 
abundances in Fig. 1 a at around log(r) = 15.5, but the peaks are not achieved (or achieved at a 
lower radius) for Fig. l(b-c) while the matter is collapsing. In case of urea, the monotonicity 
with decreasing a is not maintained. 


log(Radius in cm) 

Figure la-b. Mass fraction of complex bio-molecules as functions of logarithmic radial distance (cm). See, 
text for details of the parameters used. 

4. Observational Status 

Recently, there are reports that glycine has been seen in the interstellar clouds (Kuan et al. 
2003). Similarly there are contradicting claims (Hollis et al. 2003). The abundance that is 
observed is similar to what we predict from our model calculations. Given the uncertainly 
of the rate constants at the present moment nothing better could be done, but as we have 
used the rates in the reasonable parameter range our prediction is robust and must agree with 
the observations. Of course, the challenge would be to be able to explain all the observed 
species with chirality exactly. As our code grows with the inclusion of more complexity, 
we should be able to explain the whole set of lines, since our approach is nothing but a 


Figure Ic. Mass fraction of complex bio-molecules as functions of logarithmic radial distance (cm). See, text 
for details of the parameters used. 

numerical experiment. Meanwhile, we appeal to the experimentalists to supply us with 
pathways and rates as accurately as possible. 

5. Summary 

Simple Amino acids have been detected in meteorites coming from space, but their existence 
in star-forming region is still a mystery. We show that if we employ reasonable reaction rates, 
then they may be formed in star-forming regions during the collapse of interstellar clouds 
but whether or not they can be detected would depend on the advancement in observational 

6. Acknowledgments 

This project is supported in part by a grant from Indian Space Research Organization, 
RESPOND programme. 

7. References 

Biham, O., Furman, I., Pirronello, V. and Vidali, G. (2001), Master Equation for Hydrogen Recombination on 
Grain Surfaces, Astrophys. J., 553, 595. 

Chakrabarti, S.K. and Chakrabarti, S. (2000a), Adenine Abundance in a Collapsing Molecular Cloud, Ind. J. Phys. 
74B, 97. 

Chakrabarti, S. and Chakrabarti, S.K. (2000b), Can DNA bases be produced during molecular cloud collapse?, 
Astron. Astrophys. 354, L6. 

Herbst, E. (1992), The Production of Large Molecules in Dense Interstellar Clouds in Chemistry and Spectro- 
scopy of Interstellar Molecules, Univ of Tokyo Press. 

Hollis, J.M., Pedelty, J.A., Snyder, L.E., Jewell, P.R., Lovas, F.J., Palmer, P and Liu, S.-Y. (2003), A Sensitive 
Very Large Array Search for Small-Scale Glycine Emission Toward OMC-1, Astrophys. J., 588, 353. 

Kuan, Yi-J., Charlney, S.B., Huang, H.-C., Tseng, W.-L. and Kisiel, Z. (2003), Interstellar Glycine, Astro-phys. 
J., 593, 848. 



^Indian Astrobiology Network (IAN), Center For Space Physics, 
Chalantika 43, Garia Station Rd. Kolkata 700084, India; 

^S.N Bose National Center For Basic Sciences, JD — Block, Sector — III, 
Salt Lake, Kolkata 700098, India; ^Maharaja Manindra Chandra 
College, Kolkata 700003, India. 

I. Introduction 

Our earth is not a special place in this Universe. However, it is a planet with favorable con- 
ditions where complex bio-molecules could form and life could evolve. Chemical analysis 
of various carbonaceous chondrite like Murchison meteorite shows that plenty of organic 
molecules including eight types of biologically significant amino acids are present in them. 
Also, the spectral analysis of interstellar lines shows 124 types of molecules. Among them, 
nearly 80 species are organic and are present in the dense interstellar medium. All these 
motivate us to study the formation of bio-molecules in space. Our procedure is to couple 
hydrodynamic equations with chemical evolution of the interstellar medium (Chakrabarti 
and Chakrabarti, 2000) and the check if the complex molecules are produced in the 

2. Brief Introduction to Hydrodynamic Study 

A generic interstellar cloud may have two distinct regions. One is diffused having den- 
sity p ~ 1-10^ per cm^ and temperature 80 K and the other is the dense molecular 
cloud having density p ~ 10^-10® and temperature 10 K. Typical size of a molecular 
cloud is ~10-10‘* pc and the average lifetime is ~ 10-20 Myr. In the isothermal phase 
of the cloud collapse, density p oc r“^ (Chandrasekhar 1939) and the velocity is con- 
stant. When opacity becomes high enough to trap radiations, the cloud collapses adia- 
batically with oc In presence of rotation, centrifugal barrier forms at r = r^, where 
centrifugal force balances gravity. Density falls off as oc r“'/^ in this region (Hartmann, 
1998). Following Shu, Adams and Lizano (1987), we compute the density, temperature 
and velocity distribution inside the cloud and follow the chemical evolution at the same 


J. Seckbach et al. (eds.), Life in the Universe, 195 - 199 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


3. Chemical Evolution 

At t = 0, the chemical content of a cloud is dominated hy hydrogen and very little amount 
of other constituents. The abundance of various species (in mass fraction) of a molecu- 
lar cloud is given by, H:He:C:N:0:Na:Mg:Si:P:S:Cl:Fe = 0.64:0.35897:5.6(-4):1.9(-4): 
1.81(-3):2.96(-8):4.63(-8):5.4(-8):5.79(-8):4.12(-7):9.0(-8):1.08(-8), where, 10" is 
written as 1 . 0 (a). 

We now present a few paths to complex molecules. The production of organic molecules 
in dense interstellar clouds can occur via gas phase. Exothermic ion molecular reactions are 
most probable (endothermic reactions are not possible in the cold conditions like interstellar 
medium). The initiating process is the cosmic ray-induced ionization of H 2 (Herbst, 1992) 
to yield mainly Hj , H 2 Cosmic Ray -> Hj -f- e“-t- Cosmic Ray 

This Hj ion reacts with H 2 and produces H^, which then reacts with carbon to pro- 
duce the simplest hydro-carbon, C -|- ^CH+-t- H 2 ; CH+-|- H 2 ^CH^ -h H; CH 2 -h 

H 2 ->CH+-h H; CH+-h H 2 ^CH+-h hv; CH+-f e“ ^ CH 4 -f H; again, this could simi- 
larly produce C 3 H 3 , C 2 H 5 , CeHj , C 2 H 5 , C 3 H 7 , C 3 H 7 O, C 2 H 50 etc. which then can produce, 
N -h C 3 H+ -»HC 3 NH+-|- H. 

Similarly, ammonia NH 3 can be produced, which then reacts, CH^-f NH 3 ^ CH 3 
NH 3 -I- hv; CH^ -T HCN ^CH 3 CNH+ 4 - hv, which then produce methyl amine and aceto- 
nitrile via dissociative recombination reactions. The oxygen-containing organic molecules 
such as alcohol, acetaldehyde, dimethyl ether etc. can also be produced from the follow- 
ing reactions, CH+-f H 2 O ^CH 30 H+-f hv; H 30 +-f C 2 H 2 ->CH 3 CHOH+ 4 - hv; CH+-f 
CH 3 OH ^ (CH 3 ) 20 H+-f- hv. 

4. Effects of Grains on the Rate of Chemical Evolution 

Grains are very important constituents of interstellar medium. The chemistry on the surface 
of these grains are to be included in the chemical evolution. Main effect of these grains 
is that they influence the production of hydrogenated species such as H 2 O, NH 3 , CH 4 
etc. due to high mobility of atomic hydrogen on the cold surfaces. Therefore, we need to 
take into account the rates of such grain surface reactions as given below in the reaction 

H -h H ^ H 2 , H 2 -t- H 2 ^ H+ -h H, H -h OH ^ H 2 O, C+ + H 2 -» CH+ -f- hv, CH+ -f 
H 2 ^ CH^ + H, CH^ -|- H 2 ^ -f hv, CH 5 -|- e “ ^ CH 4 -t- H. Tunneling reactions 
with H 2 could occur once H 2 > > H. Production of bigger species does not get influenced 
very much. 

To simplify our computation, we plot in Fig. 1 a quantity representing characteristic 
size of the grain as a function of the grain size (x-axis) and note that there are three humps 
(Weingartner and Draine, 2001; hereafter WDOl). Thus we assume that three types of 
grains are important. Second, in Fig. 2 we plot the product of the area of each grain times 
the number density of each grain and And that the smaller grains have the largest surfaces, 
and therefore are the most important ones as far as the grain chemistry is concerned. For 
the time being, we use the Master equation approach for the smallest grains as suggested by 
Biham et al. (2001) and the rate equation approach for the larger two types of grains. This 
gives us the mass fraction of H 2 molecules formed due to grain surfaces as a function of the 



Figure 1. Plot of a'* dn/da as a function of the size of the grain (WDOl). 


Figure 2. Effective surface area as a function of size of the grain. 

14 16 18 

Radial Distance(cm) 

Figure 3. Plot of the saturation value of H 2 and H as a function of radial distance. 

number radius of grains. In Fig. 3 we show the expectation value of the number as functions 
of the radius of H and H 2 after saturation occurs through desorption and adsorption. 

Finally, in Fig. 4, we plot the mass fraction of the simple molecules including FI and FI 2 
as a function of the logarithmic radial distance of the cloud. These simple molecules are 
relevant to form more complex bio-molecules in these clouds. 


Figure 4. Mass fraction of simplest molecules as a function of radial distance of the cloud. 

5. Discussion and Conclusion 

More than 120 molecules have been observed in molecular cloud, more than half of which 
are organic. Some of them, especially those which contain C and N are important because 
they could be the pre-cursors of more complex bio-molecules. In this paper, we explored 
the possibilities of formation of these molecules during interstellar cloud collapse and 
star formation. During collapse, the density and temperature of the gas increases, thereby 
increasing the reaction rates of the constituent atoms and molecules. Presence of grains and 
metallic catalysts may increase the reaction rate further. We therefore discussed in details 
the effects of grains in forming H 2 molecules in the cloud. We showed how the mass fraction 
of simple molecules such as HCN, H 2 O, NH 3 etc. varies with radial distance of a collapsing 

6. Acknowledgments 

This project is supported in part by a grant from Indian Space Research Organization, 
RESPOND programme. 

7. References 

Biham, O., Furman, I., Pirronello, V. and Vidali, G. (2001), Master Equation for Hydrogen Recombination on 
Grain Surfaces, Astrophys. J., 553, 595. 

Chandrasekhar, S., (1939), An Introduction to Stellar Structure, Chicago: Univ. of Chicago Press. 

Chakrabarti, S. and Chakrabarti, S.K. (2000b), Can DNA bases be produced during molecular cloud collapse?, 
Astron. Astrophys. 354, L6. 


Hartmann, L., (1998), Accretion in Star Fomation, (Cambridge Univ.). 

Herbst, E. (1992), The Production of Large Molecules in Dense Interstellar Clouds in Chemistry and Spectro- 
scopy of Interstellar Molecules, Univ of Tokyo Press. 

Shu, F.H., Adams, F.C., and Lizano, S., (1987), Star formation in molecular clouds — Observation and Theory 
Ann. Rev. Astron. Astrophys. 25, 23. 

Weingartner, J. C. and Draine, B.T., (2001) Dust Grain-Size Distributions and Extinction in the Milky Way, Large 
Magellanic Cloud, and Small Magellanic Cloud, Astrophys. J., 548, 296. 

Implications to the Earth Enrichment 

and JOAN ORO'* 

^Institute of Geophysics & Planetary Physics, UCLA, Los Angeles CA 
90095-1567, USA. ^Institut d’Estudis Espacials de Catalunya, Spain. 

^ Departament de Quimica Inorgdnica, Universitat de Barcelona, Spain. 
^Fundacio Joan Oro, Spain. 

1. Introduction 

The overabundance of comets and chondritic bodies during the first stages of the primitive 
Solar System produced a constant rain of material over our planet, which might have direct 
implications to the origin of life on it (Oro 1961; Chyba and Sagan, 1992). Besides direct 
impacts with comets and chondritic asteroids, other important source of Earth enrichment 
in volatile and organic compounds has been the constant entry of meteoroids from dense 
meteoroid streams produced during fragmentation processes of their parent bodies. Owing 
to the large abundance of comets and asteroids in the primordial stages of the solar sys- 
tem (Delsemme, 2000), frequent encounters between minor bodies and planets should be 
expected. During a close encounter, the induced changes in the orbital elements usually 
acts by reducing the relative velocity between the Earth and the cometary or asteroidal 
fragments. Such process reduces the entry velocities of these particles, therefore decreasing 
the effects of ablation on these meteoroids, some of them very rich in organic and volatile 
content (Rietmeijer, 2002). Until recently, meteoroids have not been considered as an im- 
portant source of exogenous matter in the estimations of interplanetary mass reaching the 
Earth. Probably the main reason has been the assumption that the ablated material is de- 
stroyed during entry. Fortunately, the advances in the knowledge of the ablation processes 
provide us important evidences that this assumption, in general, is not true (Rietmeijer, 

2. Determinating the Mass Influx 

Precise information on the mass influx reaching the Earth from meteor storms is really 
scarce. Fortunately, some authors recovered recently valuable information on these streams 
in order to study the mass distribution of the particles and the flux densities. The only way 
to deduce the flux number density of old meteor outbursts is through Zenital Hourly Rates 
(ZHRs) historical visual records arrived to us from literature (Jenniskens, 1995). The ZHR 


J. Seckbach et al. (eds.), Life in the Universe, 201 - 204 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


is the number of shower meteors seen in one hour under a clear sky, the radiant at the zenith 
and the faintest visible star equal to +6.5. These standardized parameters were in the past 
not reported by observers and, in consequence, the deduced visual ZHRs are only rough 
estimations (Jenniskens, 1995). Fortunately, in the past century additional photographic and 
radar observations were made during storms, which were capable to improve the quality 
of the flux determinations in some cases (Trigo-Rodrrguez et al., 2001). ZHR are obtained 
usually from the following equation: 

ZHR = 

C ■ N ■ 

T • (sin0)f4 

( 1 ) 

Where C is a correction factor for the perception of the observer relative to an average 
observer, N is the number of shower meteors recorded in T hours of effective time, Lm 
is the limiting stellar magnitude, 6 is the elevation of the shower radiant, and r the pop- 
ulation index. To deduce the mass influx for different meteoroid streams we used a very 
simple model taking into account the population index and hourly activity observed in the 
different apparitions. The population index r corresponds to the ratio of the number of 
meteors in magnitude class M to those in class M-1 for all magnitude ranges in the different 
observational intervals. 

N(m — 1) 

( 2 ) 

We used the population index in order to reconstruct the magnitude distribution for all 
meteoroids. The next step was to derive the ZHRs taking into account the probability of 
perception for each meteor magnitude for a sky limiting magnitude of +6.5. 




The main procedure is quite simple. Our software is able to compute ZHR values from 
the proposed magnitude distribution. The magnitude origin of the distribution (Mq) is taken 
as a free parameter to obtain the ZHR values. When Mg is equal to a determinate magni- 
tude class, it implies that the number of meteors of such magnitude is one (N^ = 1). In 
order to deduce reliable ZHRs we have searched in the literature proper r and Mg values 
(Jenniskens, 1995; Trigo-Rodriguez et al., 2001; IMO Visual Data Base). The ZHR in each 
case was obtained by correcting the observed magnitude distribution for a standard proba- 
bility function (Roggemans, 1989). To compute the global mass reaching the atmosphere, 
when the magnitude distribution produces the ZHR level given in the literature, the program 
integrates the number of meteors for each magnitude class by multiplying this number by 
the mass for each class, derived from (Verniani, 1973): 

0.92 • log m — 24.214 — 3.91 ■ log Vg — 0.4 ■ (4) 

where m is the meteoroid mass in grams, Vg is the geocentric velocity given in cm-s“' and 
M„ is the magnitude of the meteor. Using these simple principles our software calculates the 
mass contribution of all magnitude classes from the meteors observed from an observing 
location. The final mass entering into the terrestrial atmosphere will be finally calculated 
considering the effective surface of the terrestrial atmosphere seen from one observing 


TABLE 1. Incoming meteoroid mass from different meteoroid streams during the annual encounters, 
outburst or storms. The spatial number density for particles producing meteoroids of +6.5 magnitude 
(P 6 . 5 ) is the number of meteoroids included in a cube with an edge of 1000 km. 







Global Mass 

Max. ZHR 


(n/10^ km^) 


Annual shower 



0,7 ± 0,2 


50+ 15 


1946 storm 



12100 + 3100 

12000 + 3000 

84000 + 22000 

1985 outburst 



160 ± 48 

700 + 100 

4500 + 1500 

Annual shower 



0.018 ± 0.006 


10 + 2 

1966 storm 



8,5 ± 2.5 

15000 + 3000 

Ks 10000 


1998 outburst 

1 . 2 / 2.0 


1700 ± 600 


100 + 5 

1999 storm 



4.6+ 1.5 

3700 + 100 

5400 + 1200 

2002 storm 



5.1 + 1.7 

4500 + 100 

6600 + 1900 


Annual shower 



0.015 + 0.004 


100 + 15 

1991 outburst 



1.5 + 0.5 

400 + 50 

500 + 150 

June Bootids 

1916 outburst 



100 + 30 

300 + 80 

150 + 50 

1 998 outburst 



145 + 35 

300 + 50 

150 + 50 

place. The considered effective area was 128 times smaller that the covered by the terrestrial 
atmosphere, this factor being the same as we used to estimate the global mass entering into 
the Earth. The involved error for well-studied storms was in the order of a factor Icr. The 
results of these models are given in Table 1 . 

Table 1 provides us the amount of cometary material that settle in the terrestrial at- 
mosphere. The incoming mass of meteoroids reaching yearly the Earth from cometary, 
asteroidal and sporadic meteoroids, integrated over the 10“® to 10^ kg range of masses, is 
around 1.2 ± 0.4 x 10® kg. From this data and assuming that the cometary flux on Earth 
followed a similar trend that the Moon cratering record, we obtained Eigure 1 . 

Figure 1. Total mass of meteoroids reaching tbe Earth. 


3. Chemical Abundances from Meteor Spectra 

In order to gain a better insight into the temperatures reached and the elements delivered 
during the ablation process, meteor spectroscopy has provided us with interesting new 
data. We have analysed recently the spectra of fireballs produced principally by cometary 
meteoroids (Trigo-Rodrfguez et al., 2003). From these spectra we have derived the relative 
abundance of Na, Mg, Ca, Si, Ti, Cr, Mn, Fe, Co and Ni in the parent meteoroids by averaging 
the composition of the radiating gas along their respective fireball path produced during 
atmospheric entry, following the methodology developed by Borovicka (1993). In general 
we have found important chemical differences between these cometary meteoroids and the 
IP/Halley dust analysed in situ by Giotto spacecraft (Jessberger et al., 1988), suggesting 
important differences between comets, as was already pointed out by Greenberg (2000). 
An interesting conclusion derived from these data is that 1 P/Halley meteoroids analysed by 
Giotto cannot be used as reference sample of cometary dust. Also, the deduced abundance 
of the major rock-forming elements Si, Mg, and Fe are in accordance to the hierarchical 
dust accretion model (Rietmeijer, 2002). 

4. Acknowledgments 

J.M. Trigo-Rodriguez is grateful to the Spanish State Secretary of Education and Universities 
for a postdoctoral grant. 

5. References 

Borovicka J. (1993) A fireball spectrum analysis, Astronomy & Astrophysics 279, 627-645. 

Chyba C., C. Sagan (1992) Endogenous production, exogenous delivery and impact-shock synthesis of organic 
molecules: an inventory for the origins of life, Nature 335, 125-132. 

Delsemme A.H. (2000) 1999 Kuiper Prize Lecture Cometary Origin of the Biosphere, Icarus 146, 313-325. 
Greenberg J.M. (2000) From Comets to Meteors, Earth, Moon and Planets 82-83, 313-324. 

International Meteor Organization, Visual Meteor Database 1988-2000. Jenniskens P. (1995) Meteor stream 
activity. 2: Meteor outbursts, A&A295, 206-235. 

Jessberger E.K., A. Christoforidis, A. Kissel (1988) Aspects of the major element composition of Halley’s dust. 
Nature 322, 691-695. 

Oro J. (1961) Comets and formation of biochemical compounds on the primitive Earth, Nature 190, 389-390. 
Rietmeijer F. J. M., (2002) The Earliest Chemical Dust Evolution in the Solar Nebula, Chemie Erde 62-1, 1-45. 
Roggemans P. (1989) Handbook for visual meteor organization, Sky Publishing Co., Massachusetts, USA. 
Trigo-Rodriguez J.M., J. Llorca J., Fabregat J. (2001) Leonid fluxes: 1994-1998 activity patterns. Met. Planet. 
Sci.,36, 1597-1604. 

Trigo-Rodrfguez J.M., J. Llorca, J. Borovicka, J. Fabregat (2003), Chemical Abundances from Meteor Spectra: I. 

Ratios of the main chemical elements. Met. Planet. Sci. 38-8, 1283-1294. 

Verniani F (1973) An analysis of the physical parameters of 5759 radio meteors, J. Geoph. Res. 78, 8429-8462. 

VIII. Earth Analogues of Extraterrestrial 



Institute of Genetics and General Biology, University of Salzburg, 
Hellbrunnerstr. 34, A-5020 Salzburg, Austria 

I. Permo-Triassic Salt Sediments 

About 250 million years ago the continents were close together and formed Pangaea, a 
supercontinent, which persisted for about 100 million years and then fragmented. The 
landmasses at that time were located predominantly in the southern hemisphere. The cli- 
mate was arid and dry; the average temperature is thought to have been several degrees 
higher than at present. This was one of the time periods in the history of the Earth, when 
huge salt sediments formed. A total of about 1.3 million cubic kilometers of salt were 
deposited during the late Permian and early Triassic period alone (Zharkov 1981). The 
thickness of the salt sediments can reach 1000 to 2000 meters. When Pangaea broke up, 
land masses were drifting in latitudinal and Northern direction. Mountain ranges such as 
the Alps, the Carpathians and the Himalayas were pushed up due to the forces of plate 
tectonics. The salt deposits in Austria originated in the Alpine basin, which extended from 
Innsbruck to Vienna. Some salt mines in the Alps are still in operation, and these were the 
sources of our samples. In the Alpine basin and in the Central European basin (Zechstein 
sea), no more salt sedimentation took place after the Triassic period; however, in other 
locations, e.g. in Poland, significant salt deposits were still formed until about 20 million 
years ago. Dating of the salt deposits by sulfur-isotope analysis (ratios of as mea- 

sured by mass spectrometry), in connection with information from stratigraphy, indicated 
a Permo-Triassic age for the Alpine and Zechstein deposits, which was independently con- 
firmed by the identification of pollen grains from extinct plants in the sediments (Klaus 

Today, salt sedimentation is taking place in surface waters with high salt con- 
tents, e.g. natural salt lakes or solar evaporation ponds. At concentrations above 15% 
NaCl, extremely halophilic archaebacteria (also termed haloarchaea) are the predom- 
inant microorganisms. Most haloarchaeal type strains have been isolated from such 
hyper-saline environments or derived materials, e.g. heavily salted foods like fish and 


J. Seckbach et al. (eds.), Life in the Universe, 207 - 210 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. High resolution field emission scanning electron micrograph of Halococcus dombrowskii H4 grown 
in liquid culture. The bar represents 500 nm. 

2. Microorganisms and Signature Sequences from Halite 

We obtained two types of rock salt samples from the salt mines at Bad Ischl and Altaussee, 
Austria: lumps of 1-2 kg of weight, which were produced by blasting for the construction 
of new tunnels, and bore cores of 5 cm diameter from exploratory deep drilling operations. 
The samples were generally from depths between 400 and 700 m below surface. Samples 
were dissolved under sterile conditions and, following addition of nutrients, investigated 
for presence and growth of haloarchaea as described previously. To date, three novel haloar- 
chaeal species from Alpine Permo-Triassic rock salt have been described, which include 
several strains of Halococcus salifodinae, one strain of He. dombrowskii (see Fig. 1) and 
one Halobacterium strain (Denner et al. 1994, Stan-Lotter et al. 1999, 2002, 2003). 

The phylogenetic tree (Fig. 2) suggests that the coccoid rock salt isolates belong to the 
genus Halococcus, hut they are sufficiently different to form separate species. The rod- 
shaped isolate strain Al is related to known Halobacterium species and even more closely 

(Strain Al (AJ548827) 

I I Strain BpA.l (AJ270239) 

Halobacterium salinarum DSM 3754^ ( AJ496 1 85) 

Haiobacterium (AB005128) 

— Natronococcus occuItus^QWi^ 2I92^(Z28378) 

J/alorubrum saccharovomm JCM 8865^ (U 1 7364) 

Halobacitium gomorrense DSM 9297^ (L37444) 

— HaloferaxvolcaniiKlQQ. 29605^ (K0042I) 
j— Haiococcus morrhua^ NRC 1 6008^ (DIM 06) 

^ Halococcus dombroH'skHX>^\A 14522^ (AJ420376) 

— Halococcus salifodinae BIp DSM 8989'*' (AB004877) 

“ Haloarcula marismorfui fiUCC 43049**^, rmA (X61688) 

^ Natronomonas pharaonis JCM 8858^ (D8797 1 ) 


Figure 2. Dendrogram showing the phylogenetic relationship of the haloarchaeal isolates from rock salt {Halo- 
coccus salifodinae BIp, He. dombrowskii H4, strains Al and BpA.l) to several genera of the Halobacteriaceae. 
The tree is based on an alignment of 16S rRNA gene sequences. Sequence accession numbers are in brackets. 
Bar represents a 1% sequence difference. 


to as yet uncharacterized isolates from other ancient salt deposits, such as the Wieliczka 
mine in Poland or the salt mine at Boulby in Britain (McGenity et al. 2000). 

Terry McGenity and Karl Stetter had investigated halococcal isolates from salt mines 
in Winsford, England, and Berchtesgaden, Germany, respectively. Their isolates Br3 and 
BG2/2 showed many similarities to our Halococcus salifodinae strain Blp, including pig- 
mentation and morphology. Therefore, all coccoid strains were analyzed in detail. They 
were found to possess identical 16S rRNA gene sequences, very similar whole cell pro- 
tein patterns, similar G -f C contents, enzyme activities, phospholipid composition, and 
other properties. From these results we concluded that in geographically separated halite 
deposits of similar age, identical species of halococci are present (Stan-Lotter et al. 1999). 
The results are consistent with the notion that a large hypersaline sea, which covered parts 
of Europe, was populated by haloarchaea, which became trapped upon sedimentation, and 
whose progeny is present today in Alpine sediments, and also in Zechstein evaporites. 

The amplification of 16S rRNA genes by the polymerase chain reaction has become 
the standard method for obtaining material for subsequent nucleotide sequencing. For this 
technique it is not necessary to cultivate the microorganisms, since the genes can be amplified 
by using DNA prepared from the sample of interest. We obtained amplification products 
from dissolved rock salt with archaeal or bacterial primers; the amplified archaeal rDNA 
was more prominent than bacterial rDNA. Following subcloning a total of fiftyfour 16S 
rRNA genes were sequenced (Radax etal. 2001); subsequently, 123 further sequences were 
obtained and analysed. The results suggested the presence of at least 1 2 clusters of sequences 
with similarities of 95%, or less, to known haloarchaeal genes, which indicated the presence 
of novel strains in the rock salt. Some sequences were similar to those of samples from other 
ancient salt deposits, such as the Wieliczka mine in Poland, or British salt mines. A few 
sequences were 92-98% similar to those of extant haloarchaea, for instance, to Halombmm 
vacuolatum and Halobacterium salinarum. 

3. Extraterrestrial Halite and Environments 

The SCN meteorites stem from Mars (Treiman et al. 2000) and contain traces of halite, as 
does the carbonaceous Murchison meteorite. The Monahans meteorite, which fell in Texas in 
1998, contained macroscopic crystals of halite, in addition to potassium chloride and water 
inclusions (Zolensky et al. 1999). The Galileo spacecraft collected evidence that support 
the existence of a liquid salty ocean on the Jovian moon Europa (McCord et al. 1998). 

These results are intriguing, since they suggest that the formation of halite with liquid 
inclusions could date back billions of years and occurred probably early in the formation of 
the solar system (Whitby et al. 2000). Could halophilic life have originated in outer space 
and perhaps travelled with meteorites; could haloarchaea have persisted in environments as 
they are found today on Mars or on Europa? 

We have started to investigate if our haloarchaeal isolates from Permian salt would 
survive Martian and other extraterrestrial conditions. We exposed several haloarchaea to a 
Martian atmosphere in the simulation chamber at the Austrian Academy of Science in Graz 
and obtained recovery rates in the order of 0.1 to 1% (Stan-Lotter et al. 2003); the addition 
of protective substances, such as glycerol, or divalent cations, increased survival rates. The 
presence of surviving cells can be visualized by fluorescent dyes, such as the LIVE-DEAD 

Figure 3. Halococcus dombrowskii cells following staining with the LIVE-DEAD kit (Molecular Probes). 
Green: viable cells; red: nonviable cells. 

kit, which allows distinction between membrane-damaged, nonviable (red) cells, and cells 
with intact membranes (green; Fig. 3). 

4. Summary 

Viable extremely halophilic archaea, representing novel strains, were isolated repeatedly 
from salt sediments, which originated from Permo-Triassic oceans. The strains appear 
to be capable of long-term survival in dry environments. Since extraterrestrial halite has 
been discovered, it seems feasible to include into the search for life on other planets or 
moons specifically a search for halophilic microorganisms. The response of haloarchaea to 
simulated Martian conditions is being investigated. 

5. Acknowledgments 

This work was supported by the Austrian Science Foundation (FWF), projects P13995- 
MOB and P16260-B07. We thank M. Mayr, Salinen Austria, for the rock salt samples. 

6. References 

Denner, E.B.M., McGenity, T.J., Busse, H.-J., Grant, W.D., Wanner, G. and Stan-Lotter, H. (1994) Int. J. Syst. 
Bacteriol. 44:774 -780. 

Klaus, W. (1974) Carinthia 11, 164, Jahrg 84: 79-85. 

McCord, T.B., Mansen, G.B., Fanale, F.P., Carlson, R.W., Matson, D.L., et al. (1998) Science 280:1242-1245. 
McGenity, T.J., Gemmell, R.T., Grant, W.D., and Stan-Lotter, H. (2000) Environ. Microbiol. 2:243-250. 

Radax, C., Gruber, C. and Stan-Lotter, H. (2001) Extremophiles 5:221—228. 

Stan-Lotter, H., McGenity, T.J., Legat, A., Denner, E.B.M., Glaser, K., Stetter, K.O. and Wanner, G. (1999) 
Microbiology 145:3565—3574. 

Stan-Lotter, H., Pfaffenhuemer, M., Legat, A., Busse, H.J., Radax, C. and Gruber, C. (2002) Int. J. System. Evol. 
Microbiol. 52: 1807-1814. 

Stan-Lotter, H., Radax, C. Gruber, C., Legat, A., Pfaffenhuemer, M., Wieland, H., Leuko, S., Weidler, G., Komle, 
N. and Kargl, G. (2003) Int. J. Astrobiol. 1:271-284. 

Treiman, A.H., Gleason, J.D. and Bogard, D.D. (2000) Planet. Space Science 48:1213-1230. 

Whitby, J., Burgess, R., Turner, G., Gilmour, J. and Bridges, J. (2000) Science 288:1819-1821. 

Zharkov, M.A. 1981. History of Paleozoic Salt Accumulation. Springer Verlag, Berlin. 

Zolensky, M.E., Bodnar, R.J., Gibson, E.K., Nyquist, L.E., Reese, Y., Shih, C.Y. and Wiesman, H. (1999) Science 



^ Laboratorio de Quimica de Plasmas y Estudios Planetarios, Instituto de 
Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito 
Exterior, Ciudad Universitaria, Apartado Postal 70-543, Mexico D.E 
04510, Mexico; ^Department of Biological Sciences, 202 Life Sciences 
Building, Louisiana State University, Baton Rouge, LA 70803, USA; 

^SETI Institute, NASA Ames Research Center, Moffett Eield, CA 
94035-1000, USA; ^ Jet Propulsion Laboratory, Pasadena, CA, 91109, 
USA; ^Instituto del Desierto y Departamento de Ingenien'a Quimica, 
Facultad de Ingenien'a, Universidad de Antofagasta, PO BOX 170, 
Antofagasta, Chile; ^Instituto del Desierto y Unidad de Bioqmmica, 
Departamento Biomedico, Facultad Ciencias de la Salud, Universidad de 
Antofagasta, PO BOX 1 70, Antofagasta, Chile; ^ Laboratoire 
Inter-Universitaire des Systemes Atmospheriques, UMR CNRS 7583, 
Universites Paris 12 & Paris 7, CMC, 61 Avenue du General de Gaulle F 
94010 Creteil Cedex, France ; and ^ Space Science Division, NASA- Ames 
Research Center, Moffett Field, CA 94035-1000, USA 

I . Introduction 

The data obtained from the Viking lander’s analyses of soils on Mars were unexpected. First, 
was the finding that when soil samples were exposed to water vapor in the gas exchange 
experiment (GE) there was rapid release of molecular oxygen, at levels of 70-770 nmole 
g“' (Oyama and Berdahl, 1977). The next puzzling result was that organic material in the 
labeled release experiment (LR) was consumed as would be expected if life would have 
been present (Levin and Straat, 1977). Lastly, there were no organic materials at levels of 
part-per-billion (ppb), as measured by pyrolysis-gas chromatography-mass spectrometry 
(pyr-GC-MS) detected (Biemann et ai, 1977); which were in apparent contradiction with 
the presence of life as detected by the LR experiment. The reactivity of the martian soil 
is currently believed to result from the presence of one or more inorganic oxidants (e.g., 


J. Seckbach et al. (eds.), Life in the Universe, 211 - 216 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


superoxides, peroxides, or peroxynitrates) at the part-per-million (ppm) level. The absence 
of organics in the soils results from their oxidation by such oxidants and/or direct ultraviolet 
radiation damage (McKay et al., 1998). 

We described here recent findings on the chemical and microbiological properties of 
soils in the Atacama Desert (Navarro-Gonzalez et al, 2003), an environment that serves 
as a model for Mars. The Atacama is an extreme, arid, temperate desert that extends from 
20°S to 30°S along the Pacific coast of South America (Miller, 1976; Arroyo et al, 1988; 
McKay et al., 2003). The extreme aridity is due to the combined effects of a high pressure 
system located on the western Pacific Ocean, the drying effect of the cold north-flowing 
Humboldf ocean currenf, fhe oceanic cloud barrier effecl of the Cordillera de la Costa, 
and the rain shadow effect of the Cordillera de Los Andes intercepting precipitation from 
the Intertropical Convergence (Arroyo et al, 1988; Navarro-Gonzalez et al, 2003). The 
Copiapo river (27° S) marks the southern limit of the extremely arid desert. The area north 
of Copiapo receives moisture from an occasional fog or a shower event every few decades 
(Arroyo et al, 1988). The region south of Copiapo starts to receive precipitation from 
the occasional winter incursions of the polar front (Arroyo et al, 1988). Proxy temper- 
ature records indicate increased precipitation from El Nino events occurred from 10 to 
16 kyr ago; however, rains did not penetrate the absolute desert region (Betancourt et al, 
2000). In addition, a 106 kyr paleoclimate record from a Salar de Atacama drill core also 
indicates episodic wet periods (Bobst, et al, 2001). Geological and soil mineralogical ev- 
idence suggest that the extreme arid conditions have persisted in the southern Atacama 
for 10-15 Myrs (Ericksen, 1983), making it one of the oldest, if not the oldest desert on 

2. Sampling Collection Sites 

Approximately 500 g representing a composite of 6 individual nearby sites (~2 m in radius) 
of the upper 10 cm soil layer were collected using sterile polyethylene scoops and stored 
in sterile polyethylene (WhirlpakTM) bags. The samples were kept at ambient temperature 
until analysis. The soil samples were collected in the driest core of the Atacama Desert, 
named the Yungay area. This area was sampled in the following sites: ATOl-03, AT02-03A 
(S 24° 4' 9.6", W 69° 51' 58.8"), AT02-03B (S 24° 4' 11.1", W 69° 51' 58.1"), AT02-03C 
(S 24° 4' 8.9", W 69° 51' 54.5"), AT02-03D (S 24° 4' 7.1", W 69° 51' 57.7"), AT02-03E (S 
24° 4' 8.3", W 69° 52' 50.1"),AT01-12 (S 24° 6' 10.2", W 70° T 9.7"), AT03-33 (S 24° 4' 
6.8’, W 69° 51' 58.1"), AT03-34 (S 24° 4' 6.2", W 69° 51' 48.4"), AT03-35 (S 24° 4' 0.4", 
W 69° 51" 49.7"), AT03-36 (S 24° 3' 50.2", W 69° 51' 51.2"), AT03-37 (S 24° 3' 44.0", 
W 69° 51' 53.3"), AT03-38 (S 24° 3' 38.8", W 69° 52' 5.3"), AT03-39 (S 24° 3' 33.0", W 
69° 52' 1 1.3"). Eor comparison a less arid site with vegetation was also studied: ATOl-22, 
AT02-22 (S 28° 7' 4.5", W 69° 55' 8"). 

The samples from the less arid site provided a control in that we used exactly the 
same methods. The “wet” sites provided positive controls for the dry sites and show that 
the relative lack of detection in the dry areas was not a failure of the methods. Blank 
tests were also run simultaneously with all methods in which no soil was added to each 


3. Results and Discussion 

3.1. PYR-GC-MS 

Analysis of samples by pyr-GC-MS at 750° C under an inert atmosphere revealed that the 
most arid zone of the Atacama, the Yungay area, is depleted of most organic molecules. 
Only two peaks in the chromatograms corresponding to organic molecules (formic acid 
and benzene) are detectable. Formic acid and benzene are present at concentrations of 
~1 jjimole g“\ and ~0.01 |xmole g“', respectively. The ratio between formic acid and 
benzene has a high value (> 12 units) indicating that the organic matter present in the region 
is oxidized, possibly composed of refractory organics such as aliphatic and aromatic mono- 
and polycarboxylic acids. 


Refractory organics present in the soil were extracted at 60° C in ethanol by sonication 
(Buch et al., 2003). Then the supernatant was filtered on a 10 |JLm MoBiTec filter and 
the solvent evaporated to dryness under nitrogen at 40° C. The dry residue was then ex- 
posed to N,N-methyl-tert-butyl(dimethyl-silyl)trifluoroacetamide in dimethyl-formamide 
using pyrene as an internal standard. The resultant volatile compounds were analyzed by 
gas chromatography coupled to mass spectrometry using a polar polydimethylsiloxane col- 
umn. The results of these analyses indicated that there are no free amino acids (< 10 "^|i,mole 
g“') in the Yungay area. The only organic compounds detected were aliphatic monocar- 
boxylic (~10“^|jLmole g“^) and dicarboxylic acids (<10”‘^|xmole g“^), and aromatic mono- 
carboxylic acids (~10“^|xmole g“*). These results support Benner’ view of the missing 
organics by the Viking landers due to the lower pyr-GC-MS temperature, e.g., 500° C 
(Benner et al, 2000). However, under our experimental pyr-GC-MS conditions (750° C), 
these organic compounds would have been degraded to formic acid and benzene at de- 
tectable levels. 


Soil samples from the Yungay area were studied for the presence of viable heterotrophic 
microorganisms by serial dilution plating on a number of artificial culture media with both 
low (1/10 and 1/100) strength Plate Count Agar (PCA) and high nutrient single strength 
PCA media. The samples contain levels of heterotrophic bacteria below the detection limits 
of dilution plating. In many cases no bacterial colonies were observed at any dilutions on 
any of the nutrient media used for plating of these samples. Extensive plating with up to 100 
replicates of samples ATOl-03 and AT02-03 and a sample from a similar site in the same 
region (ATOl-12) provided less than ten bacterial colonies in total. These data indicate that 
the Yungay area contains extremely low levels of heterotrophic bacteria. It was considered 
that there would be microorganisms entering this environment from the atmosphere, how- 
ever, they were not detected in the soil samples analyzed. Air samples were collected at site 
AT02-03 in order to determine the load of culturable microorganisms entering this environ- 
ment from the atmosphere. However, no culturable heterotrophic bacteria were obtained 


from the air samples collected in the Yungay area indicating the lack of a local source of 
airborne bacteria. Since only a small percentage of soil microorganisms can be cultured, 
DNA was extracted from the soil to construct 16S rRNA gene sequence clone libraries 
for the soil samples of the Yungay area. However, there was surprisingly no recoverable 
DNA in the Yungay soil samples studied. Contrary to results obtained in other regions of 
the Atacama, no DNA was recovered from these core region soil samples using a number 
of established DNA extraction procedures. The lack of recoverable DNA substantiates the 
absence of culturable bacteria in many of the core region soils. 


The pH of the soils is in the range 5.5 to 8.6 indicating that extreme soil pH values are 
not the cause of the low microbial numbers found in the most arid zone, the Yungay area. 
Further studies were conducted to determine if the soil from the Yungay area was toxic for 
the growth of microorganisms. The soil from AT02-03A (most arid zone) was mixed with 
the soil from the less arid site, AT02-22 (which contains about 10® colony forming units 
per gram, CFU/g), in the following ratios 1:2, 1:1, and 2:1; and then plated on 1/lOstrength 
PCA to determine the CFU/g number. The CFU/g values for these soil mixtures were not 
reduced by more than the expected dilution factor, suggesting that the soil AT02-03 A is not 


In order to understand the reactivity of the soils, we performed a modified version of the 
Viking LR experiment (Levin and Straat, 1977) with a GC-MS detection system. In one 
procedure desert soil was incubated for several days in an aqueous solution containing 
'^C-labeled sodium formate. A significant fraction (3-12 |xmole) of the formic acid added 
(~50 ijumole) was decomposed in the Yungay area (samples AT02-03A to AT02-03E) 
even where no culturable heterotrophic organisms were detected. This oxidation of formate 
to '^COa could be attributable to either abiotic or biological activity or both. However, 
formate was selected as it is thought to be the only substrate oxidized in the Viking LR 
experiment (Levin and Straat, 1977). To distinguish between any abiotic vs biological ac- 
tivity, another set of experiments were performed in which desert soil was incubated for 
several days in an aqueous mixture of two '^C-labeled chiral substrates: sodium alanine and 
glucose. Different combinations of these enantiomers were used so that any microorganisms 
present in the soil could (L-alanine + D-glucose) or could not (D-alanine + L-glucose) 
carry out metabolism. The LR response of the enantiomeric mixtures of alanine and glu- 
cose showed equal quantities of ^^C02 (~0.4 p,mole) released from both D-alanine + 
L-glucose and L-alanine + D-glucose mixtures in the Yungay area and were three orders of 
magnitude higher than those measured in the blank experiments; therefore, any biological 
explanation for the reactivity of the soil in this part of the desert can be ruled out. Degrada- 
tion of the '^C-labeled molecules was observed in the presence of hydrogen peroxide and 
sodium peroxide in control experiments while no reactivity was observed in the presence of 



The Eh of several Atacama Desert samples were oxidizing with values ranging from 365 
to 635 mV. We performed chemical assays for superoxides and hydrogen peroxide because 
these are the most plausible oxidants and are those suggested as explanations for the reac- 
tivity seen by the Viking landers (McKay et ai, 1998). They were determined by measuring 
the absorbance of crystal violet at 592 nm at pH 4, formed by the oxidation of leuco crystal 
violet by H 2 O 2 and/or O^” in the presence of the enzyme horseradish peroxidase (Zhang 
and Wong, 1994). Our results rule out these oxidants as the cause of the reactivity seen 
at the Yungay area because the concentrations are too low (0.05-0.14 ppm) to explain our 
results. Nitrates present in the soil were reduced to nitrite using powdered cadmium. The 
nitrite was then determined by diazotizing sulfanilamide and coupling with N-(l naphthyl)- 
ethylenediamine dihydrochloride to form a highly colored azo dye which was measured 
colorimetrically (Navarro-Gonzalez and Castillo-Rojas, 1995). Nitrates were found to be 
present in the soil in high levels (10-140 ppm) but they alone are not oxidizing enough 
to account for the reactivity seen in our samples. Nitrates may lead to the formation of 
peroxonitrite (NOO 2 ) and this has been suggested as a possible martian oxidant (Plumb 
et al, 1989). However the nitrate concentrations needed are in the percent level, much 
higher than in the Atacama. Thus, while our results show the presence of a strong oxidant 
in the soils in the Yungay area, the nature of the oxidant remains unexplained (Navarro- 
Gonzalez et al, 2003). Photochemical reactions initiated by sunlight continually produce 
oxidants in the lower atmosphere and surface. However, in most soils biological production 
of reduced organic material completely dominates the net redox state of soils. If biolog- 
ical production is less than the photochemical production of oxidation then the soil will 
become oxidizing. The transition from biologically dominated soils to photochemically 
dominated soils appears to be abrupt. Whichever process dominates will shift the redox 
state in one direction or another. In the Atacama there is a gradual decline in biological 
activity as conditions became drier, yet near the extreme arid region there is an abrupt 
transition to very low bacterial levels and low organic content. A gradual decline in bi- 
ological activity is observed as conditions become more arid, and in the vicinity of the 
core arid region there is an abrupt transition to very low bacterial levels and low organic 

4. Conclusion 

It is improbable that the high UV flux would have caused the oxidizing conditions found 
at the site which is only 1 km above sea level. The Atacama desert’s location and therefore 
it’s extreme aridity must inhibit the biological production of reductants and could in fact 
increase the survival of photochemically produced oxidants. Microbiological findings sug- 
gest that in the core region of the Atacama, we have found the limit of microbial survival in 
extremely desiccated environments. Since photochemical processes dominate in the core 
region of the Atacama Desert, we find almost no microorganisms, low levels of organic 
material, and the organic material present appears to have been subject to oxidation. The 
labeled-release experiments point to the presence of, as yet unidentified, oxidants in the soil. 


Many properties of these Atacama soils are analogous to the soils of Mars based on the 
current knowledge. These terrestrial soils provide an accessible resource for testing new in- 
strumentation and experiments for use in future Mars exploration(Navarro-Gonzalez et ai, 

5. Acknowledgements 

We acknowledge support from NASA ASTEP and BSRP, the National Autonomous Uni- 
versity of Mexico (DGAPA-IN 1 19999 and IN101903), the National Council of Science and 
Technology of Mexico (CONACYT No. 3253 1-T and F323-M921 1), NASA- Ames/ LSU 
Cooperative Agreement (NCC 2-5469), the National Science Foundation (Award DEB 
971427), the University of Antofagasta, and the National Center of Scientihc Research of 

6. References 

Arroyo, M.T.K., Squeo, F.A., Armesto, J.J., and Villagran, C. (1988) Effects of aridity on plant diversity in the 
northern Chile Andes: results of a natural experiment. Annals of the Missouri Botanical Garden, 75, 55-78. 

Benner, S.A., Devine, K.G., Matveeva, L.N., and Powell, D.H. (2000) The Missing organic Molecules on Mars. 
Proc. Natl. Acad. Sci. 97, 2425-2430. 

Betancourt, J.L, Latorre, C., Rech, J.A., Quade, J., andRylander, K.A. (2000) A 22,000- Year Record of Monsoonal 
Precipitation from Northern Chile’s Atacama Desert. Science 289 , 1542-1546. 

Biemann, K., Oro, J., Toulmin III, R, Orgel, L.E., Nier, A.O., Anderson, D.M., Simmonds, P.G., Flory, D., 
Diaz, A.V., Rushneck, D.R., Biller, J.E., and LaFleur, A.L. (1977) The Search for Organic Substances and 
Inorganic Volatile Compounds in the Surface of Mars. J. Geophys. Res. 30 , 4641^658. 

Bobst, A.L., Lowenstein, T.K., Jordan, T.E., Godfrey, L.V., Ku, T.-L., and Luo, S. (2001) A 106ka Paleoclimate 
Record from Drill Core of the Salar de Atacama, Northern Chile. Paleogeogr. Paleoclimatol. Paleoecol. 173 , 
21 ^ 2 . 

Buch, A., Sternberg, R., Meunier, D., Rodier, C., Laurent, C., Raulin, F., Vidal-Madjar, C. (2003) Solvent Extraction 
of Organic Molecules of Exobiological interest for in situ analysis of the Martian Soil. J. Chromatogr. (in 

Ericksen, G.E. (1983) The Chilean Nitrate Deposits. Amer. Scientist 71 , 366-374. 

Levin, G.V. and Straat, PA. (1977) Recent Results from the Viking Labeled release Experiment on Mars. J. Geo- 
phys. Res. 82, 4663^667. 

McKay, C.P., Grunthaner, F.J., Lane, A.L., Herring, M., Bartman, R.K., Ksendzov, A., Manning, C.M., Lamb, J.L., 
Williams, R.M., Ricco, A.J., Butler, M.A., Murray, B.C., Quinn, R.C., Zent, A.P., Klein, H.P. and Levin, G.V. 
(1998) The Mars Oxidant Experiment (MOx) for Mars’96. Planet Space Sci. 46 , 769-777. 

McKay, C.P., Friedmann, E.I., Gomez-Silva, B., Caceres-Villanueva, L., Andersen, D.T., and Landheim, R. (2003) 
Temperature and moisture Conditions for Life in the Extreme Arid Region of the Atacama: Four Years of 
observations Including the El Nino of 1997-1998. Astrobiology 3 , 393^06. 

Miller, A. (1976) The Climate of Chile, In: W. Schwerdtfeger (ed.) Climates of Central and South America. 
Elsevier Scientific Publishing Company, Amsterdam, pp. 1 13-145. 

Navarro-Gonzalez, R. and Castillo-Rojas, S. (1995) Lightning strikes. A simple undergraduate experiment, demon- 
strating the lightning-induced synthesis of NOx in the atmosphere. Educ. Chem. 32, 161—162. 

Navarro-Gonzalez, R., Rainey, F.A., Molina, P, Bagaley, D.R., Hollen, B.J., de la Rosa, J., Small, A.M., Quinn, 
R.C., Grunthaner, F.J., Caceres, L., Gomez-Silva, B. and McKay, C.P. (2003) Mars-Like Soils in the Atacama 
Desert, Chile, and the Dry Limit of Microbial Life. Science 302 , 1018-1021. 

Oyama, VI. , and Berdahl, B.J. (1977) The Viking Gas Exchange Experiment Results from Chryse and Utopia 
Surface Samples. J. Geophys. Res. 82, 4669^676. 

Plumb, R.C., Tantayonon, R., Libby, M., and Xu, W.W. (1989) Chemical Model fro Viking Biology Experiments: 
Implications for the Composition of the martian Regolith. Nature 338 , 633-635. 

Zhang, L.S., and Wong, G.T.F. (1994) Spectrophotometric determination of H 2 O 2 in Marine Waters with Leuco 
Crystal Violet. Talanta 41 , 2137-2145. 



^Dip. di Scienze Geologiche, Ambientali e Marine, University of Trieste 
Via Weiss, 2-34127, TS - Italy, and ^SETI Institute, NASA Ames Research 
Center, Mail Stop 239-4, Moffett Field, CA 94035, USA. 

1. Introduction 

Although the recovery of suh-basement red paleosoil (or fossil soil) dates back to the 
1980’s (e.g., Holmes, 1995), the search for organics preserved in material retrieved from 
the deep earth’ subsurface has been systematically initiated during the Ocean Drilling Pro- 
gram (ODP) Leg 197 (Emperor Seamounts, north Pacific Transect) (Tarduno et al., 2002). 
We address the astrobiology-relevant suggestion that preserved organics from extremely 
deep fossil soils in isolated diagenetic settings makes them a suitable test beds to develop 
hypotheses for future Deep Earth biosphere research and potential excellent Mars analogs. 
These soil sequences are rare in geologic collections (review in Holmes, 1995) because 
they are difficult to access (they are deeply buried —300 to —350 meters below volcanic 
basement) and sample (only by deep drilling). 

Two independent lines of evidence for the isolation of these rare paleosoils are out- 
lined here. They are: a) a model proposed for the atmosphere-ocean decoupled subsurface 
(Bonaccorsi, in press) and geochemical proxies for differentiation of the buried soils from 
their exposed counterparts, e.g., Hawaiian oxisoil (Bonaccorsi, 2002). 


Identifying organics throughout earth’s subsurface materials has implications relevant to 
astrobiological research. In fact, the detection of organics buried deep beneath the surface 
of a planet is a fundamental step to constrain the presence and evolution of life on that 
planet. This would be particularly relevant to Mars where i) low atmospheric pressure (i.e., 
4-10 mbar) and very low surface temperatures (down to — 125°C) prevent the stability of 
liquid water; and ii) high near-surface UV flux interacting with possible oxidants are likely 
to affect any near-surface and present-day life and the stability of organic molecules. 

Nevertheless, it has been suggested that previously existing life (e.g., chemosynthetic 
microbes) could have been preserved with depth on Mars (Mancinelli, 2000). This is es- 
pecially true if conditions completely different from the present-day Mars surface and 


J. Seckbach et al. (eds.), Life in the Universe, 217 - 220 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


atmosphere (decoupled conditions) occurred at some deeper locations on this planet. Hence, 
we need to identify new suitable terrestrial analogs for surface-decoupled deep settings on 
Mars and search for pristine organics deeply buried beneath subsurface materials, and 
decoupled from the Earth surface (such as the sub-basement fossil soil from OOP Leg 

Integrating microbial ecological and geochemical studies on the OOP soil samples to 
develop a model for understanding what types of organic material may serve as potential 
biomarkers for a future exploration and deep to near-surface drilling missions (i.e., soils 
sampling during landed missions) on Mars (Mancinelli, 2000). 

2. Background and Study Area 

The stratigraphy and photographs of the soil units cored at Site 1205 and Site 1206 
and the sites location map are available online at < 
197 JR/197ir.htm>. Early Eocene red paleosols were cored deeply beneath volcanic base- 
ment at Site 1205 (Nintoku Seamount, ~41°20'N; ~170°23'E) and Site 1206 (Koko 
Seamount, ~34°56'N; ~172°9'E). 

These Ee oxides/oxyhydroxide-rich soil interbeds represent the weathering product 
(tropical conditions) of mafic igneous rocks and basalts (Breccia and Plagioclase-Olivine 
basalts) and also contain hematite, magnetite, various clay minerals and palagonite (Holmes, 
1995; Tarduno et al., 2002). Importantly, they contain very low, but detectable concentra- 
tions of total organic carbon (i.e., TOC = 0.12 - 0.01%, ± 0.02%, N = 36) (Tarduno et 
al., 2002; Bonaccorsi, in press) and ultra-low nitrogen (i.e., 0.01 to 0.006, N-tot wt%). 
The single fossil soil unit (Core 197-1 206 A-40R) has stable isotope values more negative 
(i.e., 8'^C-org. = ~ — 25%o to ~ — 26%c and 8^^N-tot = — 9.5%c to 4-2. 5%c) than those 
of exposed Hawaiian counterparts (i.e., 8'^C-org = — 17%o to ~ — 23%c; and 8'^N -tot 

= 0%c to 4-8. 5%o; Bonaccorsi, in prep. Unpubl. Data). This stable isotope signature would 
suggest mixed sources of organic carbon (i.e., plant and primary/secondary bacterial), while 
values of 8'^N would indicate nitrogen fixation, nitrification, and denitrification processes 
that might have been related to some past/present microbial-induced activity (Bonaccorsi, 

3. The Model 

The model proposed for the formation of an atmosphere-ocean decoupled subsurface soil 
(Bonaccorsi, in press) consists of: a) Sub-aerial formation; b) burial and isolation from 
the atmosphere; and c) complete subsidence and decoupling from the ocean. It is expected 
that for each of those phases different organic traces were produced, preserved/altered and 
different microbial ecologies selected by changing environmental conditions. 

According to this model we have: 

1 . sub-aerial formation of soil. Red-brown soil horizons were formed on the top of 
subsiding islands by subaerial weathering o/lava flow tops or basaltic ashes during 
subaerial growth phases of the Nintoku and Koko Seamounts (emergent submarine 
volcano) and an interval of time characterized by lower eruption rates (Holmes, 


1995; Tarduno et al., 2002). More specifically, the massive to mottled red-brown 
claystones from the Pacihc are typical of tropical-subtropical soils and their clay 
mineral assemblage (smectite, kaolinite, gibbsite) indicates pedogenic oxic horizon 
formed at elevations of at least several tens of meters in lowland/upland areas such 
as those present in the Hawaiian islands today (Holmes, 1995). 

2. Burial and isolation from the atmosphere. When the volcanic activity resumed these 
soils were subsequently buried by several meter-thick lava layers flowing from land 
into water in a nearshore environment (Tarduno et ah, 2002). The accumulation of 
lava flow with burial rates (~4 to ~25 metres/lOOOy) faster than subsidence rates 
(e.g., present-day subsidence rate ~ 2.0 mm/y and 2.5 mm/y) produced a relatively 
rapid burial with the decoupling of the soil from the atmosphere. During burial soils 
underwent a variety of conditions (e.g. heating, high pressure, and diagenesis ef- 
fects), which might have caused differences from their still exposed typical tropical 
counterparts (red-brown Hawaiian oxisols, “ortox”; e.g.. Soil Survey Staff, 1975). 

3. Subsidence and decoupling from the ocean. The isolation from the Pacific Ocean 
probably occurred as a result of topographic (i.e., the upland location of soils), 
stratigraphic and tectonophysic factors (such as subsidence). 

Soils at Site 1205 and Site 1206 are barren of calcareous nannoplankton and foraminifers 
(Holmes, 1995; Tarduno et ah, 2002); in addition, they have a stratigraphic position, which is 
tens to hundred meters beneath marine deposits and basalt rock. These two lines of evidence 
would indicate that no direct contact between the soil and lagoonal/open sea waters occurred 
at the time of the two islands submergence. More likely those fossil soils were already 
buried and encapsulated in basalts prior to complete subsidence below sea level (~1 Ma to 
~2 Ma) as it is observed for similar fossil soils cored beneath the Mauna Kea today. 
Finally, the Koko and Nintoku Seamounts subsided completely below sea level (~48 Ma to 
~54 - 55 Ma) and the encapsulated soil beds likely maintained their decoupling from the 
ocean until when they were drilled. 

4. Conclusions 

There is further evidence supporting the use of the ODP fossil soils as model for Mars sub- 
surface materials: 1. Their weathered nature and iron-rich composition. 2. Their extremely 
deep setting preserving basalt and palagonite/biosignatures for >48 Ma. 3. Bacterial iso- 
tope signature. 4. Genesis and composition similar to Recent/present-day Hawaiian oxisols 
that are well-established Mars surface compositional analogs (e.g.. Bishop et ah, 1993). 
The model above outlined can help drafting hypotheses for types of organics/biosignatures 
and potential physiological types of microbes preserved in the soil material. Furthermore, 
the soil samples underwent initial heating by overrunning lava flows that may have par- 
tially altered their original composition (e.g., organics and former microbial communities) 

The existing elemental (e.g., Tarduno et ah, 2002) and stable isotope data-set (Bonaccorsi 
in prep.) need to be compared with results obtained from standard microbiological tech- 
niques. This should be done in order to establish the potential for those Eocene soils to 
serve as a suitable analog for a possible near surface to deep biosphere on Mars. 


5. Summary 

Organic-poor deeply buried red paleosoils (late Paleocene-early Eocene) were cored during 
the ODP Leg 197 (North Pacific). The fossil soil model formation (i.e., surface formation, 
deep burial and isolation from the atmosphere and the ocean) is outlined here. We suggest 
a new model based upon literature and geochemical data which suggests considering these 
fossil soils as useful samples for astrobiology relevant studies, e.g.. Mars soil analogues. One 
fundamental reason is preservation of organic traces in a deep earth system (no sun light, 
and reducing conditions), which remained isolated and decoupled from the ocean and the 
atmosphere for millions of years. This may be relevant to future studies of a possible deep 
biosphere on Mars where some preservation of subsurface to deeply buried past/present 
organics is possible. 

6. References 

Bishop, J.L., Pieters, C.M., and Bums, R.G. (1993) Reflectance and Mossbauer Spectroscopy of Ferrihydrite- 
Montmorillonite assemblages as Mars soil analog materials. Geochimica et Cosmochimica Acta 57, 4583- 

Bonaccorsi, R. Lithological features and organic content in the sub-basement fossil soil from Nintoku (Site 1205) 
and Koko (Site 1206) Seamounts, In: J.A. Tarduno, R.A. Duncan and DW Scholl (eds.) Proc. ODP, Sci. 
Results 197 (in prep). 

Bonaccorsi, R. Total Organic Carbon in Red Paleosoils and Basalts from ODP Leg 197 and their potential use as 
suitable models for Mars soil analogues. In: R. Norris (ed.) S-213 Bioastronomy 2002: Life Among the Stars 
(ASP) lAU Publications (in press). 

Bonaccorsi, R. (2002) Organic Matter and dl3C Throughout a Sub-Basement Red Soil Unit in Hole 1206A Cored 
During Ocean Drilling Program Leg 197 (Koko Seamount): First Results, Eos Trans. AGU, 83(47), Fall Meet. 
SuppL, Abstract. 

Holmes, M.A. (1995) Pedogenic alteration of basalts recovered during Leg. 144, In: J.A. Haggerty, I. Premoli-Silva, 
F. Rack, and M.K. McNutt (eds.) Proc. of the Ocean Drilling Program, Scientific Results, 144, 381-398. 

Kanavarioti, A, and Mancinelli, R.L. (1990) Could Organic Matter Have Been Preserved on Mars for 3.5 Billion 
Years? Icarus 84, 196-202. 

Mancinelli, R.L (2000) Accessing the Martian deep sub-surface to search for life. Planet. Space Sci., 48, 1035- 

Soil Survey Staff (1975) Soil Taxonomy, Dept, of Agriculture. Handbook N. 436. Washington (U.S. Govt. Printing 

Tarduno, J.A., and the Leg 197 Science shipboard Party (2002) Proc. ODP, Init. Repts., 197 [Online]: 



^Department of Applied Mathematics, RSPhysSE, The Australian National 
University, Canberra ACT 0200 Australia. ^ Department of Geology, The 
Australian National University. ^ Laboratorio de Estudios Cristalograficos, 
Instituto Andaluz de Ciencias de la Tierra, CSIC — Universidad de 
Granada, E 18002 Granada Spain. 

1 . Introduction 

The possibility of pseudofossils is a well-known obstacle to the identification of fossilized 
microorganisms (Cloud, 1973; Westall, 1999) and distinguishing abiotic from biotic origins 
is still a hotly debated topic (Dalton 2002; Schopf et al., 2002; Brasier et ai, 2002). Here 
we report silica-carbonate aggregates, so-called ‘biomorphs’ that mimic — both morpholog- 
ically and chemically-primitive microfossils. 

2. The Formation of Biomorphs and Their Resemblance to Ancient Microfossils 

A wide range of remarkable structures with curvilinear morphologies, reminiscent of simple 
biological organisms, can be produced (Figure 1). 

The synthesis of these biomorphs involves very simple reaction conditions: an alka- 
line barium-rich silica solution that, through the absorption of carbon dioxide from the air, 
promotes precipitation of these complex materials within a day. They are self-assembled 
silica-carbonate composites that display a range of morphologies, dependent on pH, temper- 
ature and concentration of the reacting molecular species (Baird et al., 1992; Garcia-Ruiz 
and Moreno, 1997 ; Garcia-Ruiz et al., 2002). The reaction is geochemically plausible in the 
Archaean era (in alkaline, siliceous hydrothermal conditions) and biomorphs could have 
been naturally produced without biological intervention (Garcia-Ruiz, 2000). Acid leaching 
produces hollow, siliceous biomorphic materials. Furthermore, these aggregates are traps 
for hydrophobic organic species (Garcia-Ruiz et al., 2002). Adsorption and thermal curing 
of small prebiotic molecules, such as phenol and formaldehyde, produces an organic skin 
covering the biomorph. This skin displays Raman spectral bands indicative of a kerogen-like 
phase (Figure 2), similar to those of the Warrawoona (micro)fossils (Schopf et al., 2002; 
Garcia-Ruiz et al., 2003). 


J. Seckbach et al. (eds.), Life in the Universe, 221 - 222 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 

Figure 1. FESEM images of biomorphs (scale bars: A, D 50 (jim; B, C 10 |J.m). 

Figure 2. Biomorph with condensed hydrocarbons (scale bar 50 (j-m) and Raman spectra of carbonaceous 
coating (Garcfa-Ruiz et al., 2003). 

A purely inorganic route to the formation of carbonaceous microstructures with mor- 
phologies very similar to the most ancient microfossils has been demonstrated. These abi- 
otic materials fulhll morphological and chemical criteria for biogenicity (Garcia-Ruiz et al. , 
2003). Therefore, the use of kerogen signatures and structural resemblance to modern bac- 
teria cannot alone act as indicators of biogenicity. Abiotic formation of “microfossils” must 
be ruled out before biogenicity can be considered. The implications for the search and 
identihcation of the earliest of life forms are profound. 


Baird, T., Braterman, P. S., Chen, P., Garcia-Ruiz, J. M., Peacock, R. D. and Reid, A. (1992) Morphology of 
gel-grown barium carbonate aggregates — pH effect on control by a silicate-carbonate membrane. Material 
Research Bulletin 27, 1031-1040. 

Brasier, M. D., Owen, R. G., Jephcoat, A. R, Kleppe, A. K., van Kranendonk, M. J., Lindsay, J. F., Steele, A. and 
Grassineau, N. V. (2002) Questioning the evidence for Earth’s oldest fossils. Nature 416, 76-81. 

Dalton, R. (2002) Sqaring up over ancient life. Nature 417, 782-784. 

Cloud, P. (1973) Pseudofossils: A plea for caution. Geology 1, 123-127. 

Garcia-Ruiz, J. M. (2000) Geochemical scenarios for the precipitation of biomimetic inorganic carbonates. In: 
J. P. Grotzinger and N. P. James (eds.). Carbonate sedimentation and diagenesis in the evolving Precambrian 
world. SEPM special publication 67, 75-89. 

Garcia-Ruiz, J. M. and Moreno, A. (1997) Growth behaviour of twisted ribbons of barium carbonate/silica self- 
assembled ceramics. Anales de Quimica Int. Ed 93, 1—2. 

Garcfa-Ruiz, J. M., Camerup, A. M., Christy, A. G., Welham, N. J. and Hyde, S. T. (2002) Morphology: An 
ambiguous indicator of Biogenicity. Astrobiology 2, 353-369. 

Garcfa-Ruiz, J. M., Hyde, S. T., Camerup, A. M., Christy, A. G., Van Kranendonk, M. J. and Welham, N. J. (2003) 
Science, in press. 

Schopf, J. W., Kudryavtsev, A. B., Agresti, D. G., Wdowiak, T. J. and Czaja, A. D. (2002) Laser-raman imagery 
of Earth’s earliest fossils. Nature 416, 73-76. 

Westall, F. (1999) The nature of fossil bacteria: A guide to the search for extraterrestrial life. Journal of geophysical 
research, 104noE7, 16437-16451. 



^Instituto de Ciencias Bdsicas. Universidad Veracruzana. Carr. 
Xalapa-Ver, Km. 3.5, Xalapa, Ver, Mexico, ^ NASA-Ames Research Center. 
Moffett Field, CA 94035, USA, and ^ Laboratorio de Qmmica de Plasmas y 
Estudios Planetarios. Instituto de Ciencias Nucleares, UNAM, Circuito 
Exterior, Ciudad Universitaria, Apartado Postal 70-543, Mexico. 

1. Introduction 

In low latitude regions of the Earth we hnd surface temperature near 0° C in tropical alpine 
environments (Perez-Chavez et ai, 2000). In these environments temperature and pressure 
rapidly decrease as the altitude increases and so organisms must adapt to them until they 
reach their physiological tolerance limits. A clear example of this is treeline at thermal 
gradients that represent an abrupt transition in life form dominance. In Pico de Orizaba, 
Mexico (19° N), there are such environments which can be used as plausible analogues for 
ancient and future life on Mars. 

2. Methods 

Several locations in the mountain were selected above, below and within the treeline of 
Pico de Orizaba (Cruz-Kuri et ai, 2001). In each station, we register relative humidity, air 
temperature and soil temperatures at various depths (up to 40 cm). 

3. Results and Discussion 

The meteorology in and outside treeline seems to be quite interesting. The temperature 
is modulated by a wave with a period of approximately twenty days; of course there is 
also the daily periodicity. This suggests performing more precise types of analyses for the 
corresponding time series. For each station and for every logger, cross-correlations of the 
corresponding time series were calculated. The time lags varied from —360 hours to -|-360 
hours in units of 1 hour. Also, analyses of correlation were performed for the smoothed 
time series with daily averages, with minimum and with maximum temperatures; in this 
situation, the time lags were selected to vary from -28 to -t-28 days in units of 1 day. 
In addition, spectral analysis were performed for each series. From the resulting graphs it 


J. Seckbach et al. (eds.), Life in the Universe, 223 - 224 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


-32 -24 -16 -8 0 8 16 24 32 

-32 -24 -16 -8 0 8 16 24 32 

Lag Number Lag Number 

Figure 1. Cross correlations Temperature 1 (soil level) with Temperature 2 (10 cm depth) and with 
Temperature 3 (20 cm). Station NB, November 2002-March 2003. Time lags are from —36 to -t-36 hours. 

became apparent that there are several patterns and that there is a 24-hour periodicity (which 
can be accounted for by the obvious natural phenomena) as well as a 7-day periodicity (for 
which no natural phenomena follows a seven-day cycle). A plausible explanation is that of 
human activity, is perturbating remote areas of the Earth. We have found some correlograms 
that even when they exhibit a daily periodicity, all the cross-correlations are positive; other 
ones for which the correlations are all negative; for others, some of the correlations are 
positive and some are negative. In the case of loggers which record soil temperatures at four 
depths, above patterns are related to heat conductions in the soil, for different types of soil 
as well as the air temperatures, the humidity and other climate variables. For some stations, 
the cross correlations were close to unity, thus indicating that the heat is transmitted very 
rapidly from one depth to the next ones. In other stations, the correlations are small. For 
others, the flow of heat has a reversal in direction as time goes on. Only one of the patterns 
is illustrated below. 

4. Conclusions 

The multivariate time series analysis makes apparent that the soil temperatures are driven 
by some other external climatic parameters. Understanding what type of relationships hold 
will greatly contribute to determine which factors are the most important ones in order to 
explain the positions of the treelines. 

5. References 

Cruz-Kuri, L., McKay, C. P. and Navarro-Gonzalez, R. (2001) Spatial and Temporary Patterns of Some Climate 
Parameters Around the Timberline of Pico de Orizaba, In: J. Chela-Flores, T. Owen and F. Raulin (eds.) 
Astrobiology: First Steps in the Origin of Life in the Universe, Kluwer Academic Publishers, pp. 293-301. 
Perez-Chavez, I., Navarro-Gonzalez, R., McKay, C. P. and Cruz-Kuri, L. (2000) Tropical Alpine Environments: 
A Plausible Analogue for Ancient and Future Life on Mars, In: J. Chela-Flores, G. A. Lemarchand and J. Oro 
(eds.) Astrobiology: Origins from the Big-Bang to Civilisation, Kluwer Academic Publishers, pp. 297-302. 

IX. On the Question of Life on Mars and 
on the Early Earth 



^Centre de Biophysique Moleculaire, Rue Charles Sadron, 45071 Orleans 
cedex 2, France, ^Planetary and Space Sciences Research Institute, The 
Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom 
^ Space Research Centre, Department of Physics and Astronomy, University 
of Leicester, University Road, Leicester, LEI 7RH, UK 

I. Introduction 

The search for traces of life on Mars is presently focused on robotic in situ analyses (Westall 
et ah, 2000) and the study of Martian meteorites (Brack and Pillinger, 1998). The early 
histories of Mars and Earth clearly show similarities. Geological observations from data 
collected by Martian orbiters suggest that liquid water was once stable on the surface of 
Mars. Mapping of Mars by Mariner 9, Viking 1 and 2, and by Mars Global Surveyor, revealed 
channels resembling dry river beds. Odyssey’s gamma ray spectrometer instrument detected 
hydrogen (Boynton et al., 2002), which suggested the presence of water ice in the upper 
metre of soil, in a large region surrounding the planet’s south pole, where ice is expected 
to be stable. The amount of hydrogen detected indicates 20 to 50 percent ice by mass in 
the lower layer beneath the top-most surface. The ice-rich layer is about 60 cm beneath the 
surface at latitude 60°S, and approaches 30 cm of the surface at latitude 75°S. 

The Viking 1 and 2 lander missions were designed to address the question of extant 
life on Mars. The results were ambiguous, since although “positive” results were obtained, 
no organic carbon was found in the Martian soil, on the basis of measurements by gas 
chromatography-mass spectrometry. It was concluded that the most plausible explanation 
for these results was the presence, at the Martian surface, of highly reactive oxidants such as 
H 2 O 2 , which would have been photochemically produced in the atmosphere (Hartman and 
McKay, 1995). Direct photolytic processes can also be responsible for the dearth of organics 
at the martian surface (Stoker and Bullock, 1997). The Viking lander could not sample soils 
below 6 cm and therefore the depth of this apparently organic-free and oxidising layer 
is unknown. Bullock et al. (1994) have calculated that the depth of diffusion for H 2 O 2 is 
less than 3 metres. The alpha proton X-ray spectrometer (APXS) on board the rover of the 
Mars Pathfinder mission measured the chemical composition of six soils and five rocks at 
the Ares Vallis landing site in 1997. The analysed rocks were partially covered by dust or a 
weathering rind similar in composition to the dust. Some rocks were found to be similar to 
terrestrial andesites, but it is not certain that these rocks are igneous. The texture of other 
rocks is difficult to interpret and might be sedimentary or metamorphic (Rieder et al., 1997). 


J. Seckbach et al. (eds.), Life in the Universe, 227 - 231 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Beagle 2, the exobiology lander of ESA 2003 Mars Express mission, has been designed 
to search for evidence of life in subsurface and rock interior samples taking into account 
that the search for traces of life on Mars must necessarily be coupled with a geochemical 
exploration of the surface and near subsurface. 

2. The Landing Site 

Beagle 2 will land on Isidis Planitia, a large flat region which overlies the boundary be- 
tween the ancient highlands and the northern plains. Isidis Planitia (11.6°N, 90.75°E) is a 
sedimentary basin, in fact, the third largest impact basin on Mars. It lies at ~10°N, which 
is the maximum latitude for a site to be warm enough for Beagle 2 to function properly. 
The number of rocks on the surface seems to be about right: not too much to threaten a safe 
landing, but enough for the sampling operations. The site is at a low enough elevation to 
allow the parachutes sufficient atmosphere to brake the lander descent. 

3. Sample Collection 

Protected samples will be acquired, by the rock corer, from the inside of any large rock 
which can be reached by the robotic arm. The 0.7 m robotic arm will also support all the 
instruments at once, a concentration referred to as Beagle 2 PAW, for Position Adjustable 
Workbench. The surface of the rocks will be ground (rock grinder) and the rocks will be 
investigated before and after grinding. 

Another kind of protected sample will be acquired by the mole: from below the harsh, 
oxidising surface — if possible, from a region additionally protected by a boulder large 
enough not to have been disturbed since being emplaced. Developed by DLR Cologne, in 
conjunction with Transmash (Russia) and Technospazio (Italy), initially under the auspices 
of ESA TRP funding, the mole will provide an element of mobility to the stationary lander. 
The mole has the ability to crawl across the surface at the rate of 1 cm every six seconds, 
using a compressed spring mechanism to propel a drive mass. Samples are to be collected in 
the jaw-like mouth. It is expected that the mole will be able to crawl up to two metres away 
from the lander, including the burrowing phase; it is recovered by winding in the cable. The 
robotic arm aids the sample delivery from the mouth of the mole, into the opening to the 
miniaturised laboratory which is located inside the lander. The mole has a total weight of 
900 g and power consumption of only a couple of watts. In addition to horizontal movement, 
the same process hammers the mole into the ground or under boulders a millimetre at a 
time in a vertical movement. 

4. Cameras 

The Beagle 2 lander carries three cameras: 

• A stereo pair of cameras mounted on the robotic arm will provide a panoramic view 
of the scene around the landing site and monitor the activities during sampling. 


• One of the cameras is equipped with a pop-up mirror which will provide the first 
wide angle picture of Mars soon after landing without having to lift the robotic arm 
from its stowage position. 

• A third camera is part of a microscope, deployed by the robotic arm which will be 
used to examine fresh rock surfaces cleaned of weathered debris by a rock grinder. 
The microscope with 4 micron resolution will image at various wavelengths 

5. Stepped Combustion and Gas Analysis Package 

The solid sample (soil or rock) will be heated in steps of increasing temperature, and sup- 
plied with freshly generated oxygen at each increment. Any carbon compound present will 
burn to give carbon dioxide. The gas generated at each temperature will be analysed by 
the mass spectrometer. The instrument can distinguish between the two stable isotopes of 
the carbon and quantify the ratio. Other gases can be analysed by the same instrument, 
including methane. The design for the mass spectrometer is based on a 90° sector analyser 
and incorporates a magnet, weighing less than 1 kg, made from samarium-cobalt, together 
with an ion pump using the same material. It will operate in dual inlet mode, whereby 
samples and standards are sequentially compared, for high precision isotopic measure- 
ments; alternatively, for greatest sensitivity, the instrument can operate in static vacuum 

6. Spectrometers 

The Mossbauer spectrometer will provide information about the oxidation state of iron 
in mineral samples. It will be used to determine the degree to which iron is in the ox- 
idised form, Fe(III). The X-ray detector on Beagle 2 will provide elemental composi- 
tions from the energy spectrum of X-rays produced by bombarding samples with X-rays 
from ^^Fe and *°®Cd sources. A potential objective is measurement of the potassium 
content, for age dating purposes in conjunction with ‘^®Ar determination from the Gas 
Analysis Package. Quantifying major elements Mg, Al, Si, S, Ca, Ti, Cr, Mn and Fe and 
trace elements will help in identifying rock types and aid the interpretation of Mossbauer 

7. Environmental Sensors 

A suite of seven environmental sensors to provide measurements of the conditions on Mars 
with respect to its suitability for life and climatic parameters: 

- An ultraviolet sensor to detect surface UV flux at 200-400nm. 

- ESOS, a thin film able to detect an oxidising atmosphere. 

- A radiation sensor to measure the total long term dose and dose rate of solar protons 
and high energy cosmic rays. 


- Thermocouples which can detect air temperature variations to within ±0.05K. 

- A pressure sensor which will measure both day and night air pressure to an accuracy 
of O.lmBar. 

- A wind gauge to monitor speed (to 0.1 m/s) and direction (to 5°) 

- Dust impact detectors to register the momentum, direction and rate of martian 

8. Beagle 2 and Art 

Beagle 2 is also the name of the music specially composed by the British rock band Blur 
for the project. Beagle 2 will be the call sign for the lander and will be beamed back from 
the surface of Mars to announce our safe arrival. The British artist Damien Hirst provided 
an image on the lander based on his famous spot paintings, which will serve as the colour 
calibration target for the on-board cameras. By using various iron oxides and other known 
minerals it will also be possible to obtain signals to standardise the Mossbauer and X-ray 

9. The Beagle 2 People 

The Beagle 2 Team comprises/compromised of C.T. Pillinger (Beagle 2 Consortium 
Leader), M.R. Sims (Beagle 2 Mission Manager), K. Arnold, C. Ashcroft, R. Asquith, 
C. Berry, M. Bonnar, A. Brack (Chairman of the Adjunct Science Team), G. Butcher, J. 
Clemmet, A. Coates, R. Cole, J. Dowson, W. Edwards, A. Ewbank, C. Farmer, G. Fraser, 
J. Gebbie, A. Griffiths, I. Hindle, A. Holland, H. Hamacher, S. Hurst, G. Johnson, J.L. 
Josset, B. Kirk, G. Klingelhofer, H. Kochan, M. Leese, R. Marston, D. Moore, G. Morgan, 
N. Nelms, G. Paar, S. Peskett, N. Phillips, D. Pullan, L. Richter, T. Ransome, N. Roskilly, 
A. Senior, B. Shaughnessy, M. Sherring, R. Slade, A. Smolen, A. Spry, J. Standing, J.L.C. 
Stewart, R. Sulch, J. Sykes, J. Thatcher, N. Thomas, M. Towner, J. Underwood, L. Waugh, A. 
Wells, S. Whitehead, R. Wimmer, D. Wright, I.P. Wright, and J. Zarnecki with contributions 
from many others. 

10. References 

Boynton, W.V., Feldman, W.C., Squyres, S.W., Prettyman, T.H., Briickner, J., Evans, L.G., Reedy, R.C., Starr, R., 
Arnold, J.R., Drake, D.M., Englert, P.A.J., Metzger, A.E., Mitrofanov, L, Trombka, J.I., d’Uston, C., Wanke, 
H., Gasnault, O., Hamara, D.K., Janes, D.M., Marcialis, R.L., Maurice, S., Mikheeva, I., Taylor, G.J., Tokar, 
R. and Shinohara, C. (2002) Distribution of Hydrogen in the Near Surface of Mars: Evidence for Subsurface 
Ice Deposits, Science, 297, pp. 81-85. 

Brack, A. and Pillinger, C. (1998). Life on Mars: chemical arguments and clues from Martian meteorites. Ex- 
tremophiles 2, 313-319. 

Bullock, M.A., Stoker, C.R., McKay, C.P. and Zent, A.P. (1994) A coupled soil-atmosphere model of H 2 O 2 on 
Mars, Icarus, 107, pp. 142-154. 

Hartman, H. and McKay, C.P. (1995) Oxygenic photosynthesis and the oxidation state of Mars, Planet. Space Sci., 
43 , pp. 123-128. 


Rieder, R., Economou, T., Wanke, H., Turkevich, A., Crisp, J., Bruckner, J., Dreibus, G. and McSween, Jr., 
H.Y. (1997) The chemical composition of Martian soil and rocks returned by the mobile alpha proton X-ray 
spectrometer: preliminary results from the X-ray mode. Science, 278, pp. 1771-1774. 

Stoker, C.R. and Bullock, M.A. (1997) Organic degradation under simulated Martian conditions, J. Geophys. Res., 

102, pp. 10881-10888. 

Westall, F., Brack, A., Hofmann, B., Homeck, G., Kurat, G., Maxwell, J., Ori, G.G., Pillinger, C., Raulin, F., 
Thomas, N., Fitton, B., Clancy, R, Prieur, D. and Vassaux D. (2000) An ESA study for the search for life on 
Mars. Planet. Space Sci. 48, pp.181-202. 



Instituto de Ciencias Avanzadas, A.C., Xalapa, Ver., Mexico 

Abstract. An alternative independent device for terraforming a planet is propossed. It will 
have an inner ecosystem protected from the outside which will interact with the surroundings 
and will began a microterraforming process. Such structure will be for Mars what cells are 
for plant life form, supporting the planet’s oxygenation and global warming at a time, via the 
atmospheric densification. 

I. Introduction 

The main proposal for the process of terraforming Mars lead to a global warming of the planet 
by using several methods such as the one proposed by Lovelock & Allyby ( 1984) comprising 
a model for the addition of super green house gases, which was developed at the beginning by 
Lovelock, Allaby (1984) y Fogg (1989). Afterwards, Zubrin and McKay (1997) elaborated 
a model where they proposed the use of orbital mirrors that would reflect sun’s rays directly 
into Mars South Pole, which has more frozen CO 2 ; they proposed as well the use of 
chemical ground processing factories in order to extract CO 2 and achieve the increase 
of the green house effect and density the atmosphere. Finally, Marinova (2000) and Gestell 
(2001) propossed the addition of super green house gases by using perfluorocarbonate, 
microorganism and chemical factories. 

2. The Minimal Unit of Terraforming 

The current tendency for Mars terraforming is the global warming of the planet. How- 
ever, this document suggests a model for terraforming Mars in sections with a device 
called the Minimal Unit of Terraforming (MUT) which implies an ecosystem as the 
main unit of nature, comprising a group of living organisms and their chemical and 
physical environment where they live, but applied to a remodelling and colonization on 
Mars. The MUT will be dome shaped structures built from ground stuck translucid plas- 
tic trends that will interact with the surroundings helped by gas exchange and biolog- 
ical ground prosecution. As a consequence, they will help to the rehabilitation of the 
surface and the creation of photolithographic and chemicalautotrophic organisms. They 
will take the CO 2 from the atmosphere via the photosynthesis by releasing the oxy- 
gen. Then, the MUT collaborate as well on the ground gas reduction process creating a 


J. Seckbach et al. (eds.), Life in the Universe, 233 - 237 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


difference in the temperature and releasing the gases out to the atmosphere for its densifi- 

Gaia principles hy J. Lovelock and L. Margulis had been considered for the establishment 
of an environment inside the MUT since life means plasticity and it can be adapted and adapt 
the surroundings by bringing climate and biological balance. Life sown inside the MUT 
will not have an ecosystem like that of the Earth and Mars, but a neutral ecosystem which 
means the devices will be in thermodynamic lack of equilibrium with the Martian surface. 
Life will respond then to the dome weather conditions helped by life plasticity and would 
begin to adapt the inside according to its needs. Then, these structures would be located at 
latitude 20 degrees above and 20 degrees under the ecuatorian Martian region. The reason 
for its establishment on those latitudes is for its weather conditions, since the maximum 
temperature reaches 20° C and the minimum —140° C, moreover the atmospheric pressure 
fluctuates between the 7 and 10 milibars where the sun light rate is 43% higher than that 
received on Earth. 

3. Minimal Unit of Terraforming Operational Model 

The MUT should be capable of generate the water and energy need in order to give the inner 
environment could do its job of CO 2 receiving and increase its biomass. For that purpose 
the domes will have valves over their tops which will allow the access of martian air and 
the egress of photosynthetic gases. The valve functions will be the following: a) to let the 
entrance of martian air for the increasing of the MUT’s inner pressure, achieving water 
existence; b) to let CO 2 enter the domes for photosynthetic purposes and for stabilization 
of partial pressures in the inside; c) exit of the resulting gases from photosynthesis such as 
oxygen and the degassing as steam. 

The atmospheric pressure inside could stabilize in 60 milibars, since with that pressure; 
plants are in state of function properly. The resulting oxygen from the photosynthesis will 
be accumulating inside the MUT. After a while, the valves will activate releasing inner 
pressure so that the inner atmosphere escapes together with the generated oxygen. As a 
result, the amount of milibars will decrease in the inside and when the pressure reach 
40 milibars an antenna will detect this decrease and will activate a device that will close 
the valves. With that, other valves will activate and they will let enter sucked in air from 
the outside and with that increase the inner pressure to the original 60 milibars. Martian 
air, containing 95 percent of CO 2 will be entering the MUT; however, this entrance should 
be regulated which means the partial pressures in the inside would have to be considered 
to avoid an acidosis in the plants (Hiscox, 1996) therefore, the death of the environment. 
Moreover, will have to be tolerant in high CO 2 levels. Hence, a gradual adaptation to a CO 2 
concentrated environment should take place. The MUT will create a green house effect, 
which warmth will permit water existence, for which warmth generation and retention in the 
inside will be essential for the ecosystem growth. To achieve that aim, the dome should be 
a thermal structure that will avoid warmth liberation and cold access, protecting the inside 
from the Ultraviolet rays. The energy flow depends on the incidence of sun light, which in 
Mars are 500 watts/m2 warmth. This is important because it will determine the strength of 
the warming to permit the ground degassing process and the action of the photosynthetic 
organisms inside the MUT. The warmth concentration of the MUT will contribute to the 


release and storage of water via plant tissues, in which warmth will be extremely important 
in the activation of the inner hydrological cycle. It is known that Mars has water, but it is 
captured in the poles, in the underground and creating permafrost on the surface (Vazquez & 
Guerra, 1995); nevertheless, there is certain atmospheric moisture that may condensate and 
canalize into the dome for benefit of the inner ecosystem. A way of achieving this is through 
the zeolite, a mineral with important absorbent properties, which will take moisture from 
the martian atmosphere. Adam Bruckner (1995), propossed the use of a zeolite condenser, 
which could be part of the solution of water taking and its irrigation to the inside of the 
MUT. It can be obtained through photoelectric cells which will be constantly charging a 
battery system. 

4. The Inner Ecosystem 

The MUT could be considered as oxygen makers and processors of the martian surface. 
They will be balanced with the surroundings. The solar light that Mars receive is appropriate 
for the photosynthetic processes. However, the photosynthetic efficiency will depend on the 
amount of solar light on Mars, which is higher 43% than that of the Earth. The MUT will 
maintain the inner temperature, specially at night, protecting the plants from potential death 
by freezing. The ecosystem could be shaped by pioneer cosmopolitan, ground disintegrating 
and creating plants such as the bryophytes. These lead us to repeat an evolutive pattern that 
happened on Earth during the invassion of sea plants to the surface. Other possible organisms 
are plants from cold deserts such as the saxyfrague, and from high mountains such as the 
soldanella, which are water storing plants, the succulent and trees such as pines, specially the 
pinus hartwegii lindl. Other pioneer organisms are the gramineous, which are cosmopolitan 
as well and could be ideal for the formation of fertile ground. The pine species that could 
be part of the environment of the MUT are; P. ayacahuite var. Veitchii Shaw, P. Johannis 
Robert, P montezumae var. Lindleyi Loud, P hartwegii Lindl, and white P. cooperi which 
annual temperature ranges between —20 and 40 degrees C, and are located between 1500 
to 4000 meters height. These pines have an electric charge that can express high resistance, 
favoring their ability of acclimatization. The ecosystems inside the MUT will gradually 
acclimatize to the planet’s condition and they will be adapting Mars weather to their own 
conditions, with a feedback result. The consequence is a balanced point between the actual 
condition of the planet and that inside the MUT. Therefore, the MUT and their ecosystems 
in Mars will work according to the interaction Genotype + Environment has as a result 
phenotypical expressions that modify and form the planet’s environment. The afore exposed 
ideas can be expressed as follows: 

G + Ei = '^P + MEi = E2 (1) 

Whereas G is the Genotype, Ei is the Initial Environment, are the Phenotypical Ex- 
pressions, the MEi is the Initial Modelling of the surrounding or the resulting environment 
of the phenotypical expression and E 2 is the final resulting stabilized environment. However, 
the development and growth of the species inside the MUT will be in close relation with 
environmental factors and the available mineral nutrients. This is due to restriction factors 
according to the Liebig Law, (Odum, 1976) which refers to the minimum of nutrients an 


organism requires to live, which means that what is required inside the MUT is a euri 
environment. The martian ground (Zubrin, 1997) has enough nutrients for plant develop- 
ment, even in a higher amount than in Earth. Apart from nitrogen, which percentage is 
unknown and it is critical for the protein formation, could cause problem for its addition 
due to its low atmospheric concentration. Each unit will help with the atmospheric den- 
sification, therefore the addition of all the units that are spread over a martian given area 
will have to affect the current environment of the planet. In fact, a green house and a 
degassing effect will be generating in the inside of the unit, as suggested by Zubrin and 
McKay, but in the MUT the phenomenon is faster. Therefore, if a program comprising the 
installation of colonies and colony groups of MUT is accepted, simultaneously, a plant 
colonization and atmospheric processes, moreover each unit could be an experimental base 
which will feed with data the development, evolution, and improvement of plant colonies in 

5. Conclusion 

The MUT creates a thermodynamical disturbance of the environment in which they are 
exposed, generating an energy rich environment, supporting life development, which will 
gradually affect the martian environment, which will produce an effect on the genotypes 
of the various species developed in the MUT, creating a feedback system. With that sys- 
tem, Mars could be gradually terraformed, and its duration will depend on the number 
of MUT installed on the surface, because they will interact directly with the atmosphere 
and the ground and the consequence will be the reconversion generated by the interaction 
Genotype -|- Environment. However, not only the martian environment will be affected and 
remodelled, but the organisms of the environments, since an speciation process will look 
for its own firmness according to Liebig Law. 

6. Acknowledgements 

I want to thank very much Dr. Julian Chela-Flores for his important support for my partic- 
ipation in The Seventh Trieste Conference on Chemical Evolution and the Origin of Life. 
I want to thank as well, members of the Institute de Ciencias Avanzadas A.C., Mr. Cirilo 
Santiago Cruz, Julieta Ivette Ramirez Enriquez and David Armando Morales Enriquez as 
well as all the people who supported me. 

7. References 

Allaby, M. and Lovelock, J. (1984) The greening of Mars, St Martin Press, New York. 

Lovelock, J.E. (1985) Gaia. Una nueva vision de la vida sobre la Tierra, Ediciones Orbis, Madrid, Espana. 
Hiscox, J.A. (1996) Biology and the planetary engineering of Mars. Department of Microbiology, University of 
Alabama, Birmingham, USA. 

Odum, E. P. (1976) Ecologia, C.E.C.S.A. Mexico. 

Odum, H.T., Odum, E.C., Brown, M.T., LaHart, D., Bersok, C., Sendzimir, J. (1988) Environmental Systems and 
Public Policy, Ecological Economics Program. University of Florida, USA. 


Vazquez Abelardo, M. and Guerrero de Escalante, E.M. (1999) La busqueda de vida extraterrestre, McGraw-Hill, 

Williams, J. D. Coons, S.C., and Bruckner, A.P. (1995) Design of a Water Vapor Absorption Reactor for Martian 
in situ Resource Utilization, J. of the Brit. Interplanet. Sod. 48, 347—354. 

Zubrin, R. and C.R McKay (1993) Technological requirements for terraforming Mars. AIAA 93-2005. 1-14, 29th 
Joint Propulsion Conference and Exhibit. 

Zubrin, R. (1997) The case for Mars, Touchstone, New York. 



Centre de Biophysique Moleculaire, CNRS, Rue Charles Sadron, 45071 
Orleans cedex 2, France 

1. Introduction 

After a number of decades of research on the evidence for life in the Early Archaean epoch 
(4.0-3. 2 Ga), recent controversies have thrown the very concept of the existence of life on 
Earth in this time period into discussion (Brasier et al., 2001; Lindsay et al., 2003; Westall 
and Folk, 2003; van Zuilen et al., 2002, 2003; Lepland et al., 2002). In this contribution I 
will review the discussions, describe the procedures that should be followed in the search 
for fossil life, and briefly document the evidence for widespread and relatively abundant 
life in 3. 5-3. 3 Ga sediments. 


Greenland hosts the oldest sedimentary rocks on Earth (>3.7 Ga) at Isua and Akilia; they 
are, however, severely metamorphosed and deformed. The evidence for life at the time 
these rocks were formed is based on carbon isotope measurements (Shidlowski, 2001; 
Mojzsis et al., 1996; Rosing, 1999), and on observations of carbonaceous microfossils 
(Pflug and Jaeschke-Boyer, 1979; Robbins, 1987; Pflug, 1979, 2001). However, problems 
related to recent contamination of the rocks samples, as well as a metamorphic production 
of graphite, were highlighted by van Zuilen et al. (2002) and Westall and Folk (2003). 
One isotopic signal from rocks that are thought to have been deep-sea sediments (— 18%o, 
Rosing, 1999) appears, however, to be original and is neither a product of contamination 
nor of later metasomatic origin. 



Barberton Mountain Land (South Africa) and the Pilbara Craton (Australia) are the locations 
of the oldest, well-preserved sedimentary rocks on Earth. Relatively large, filamentous, 
carbonaceous structures were described from the silicified sediments as fossil cyanobacteria 
(relatively evolved, oxygen-producing photosynthetic bacteria), although a few rare, smaller 
filaments were described as filamentous bacteria (Schopf, 1993; Walsh, 1992). Recently, 
the interpretation of cyanobacteria has been challenged (Brasier et al., 2001) on the grounds 
that (1) the original sample actually came from the interior of a hydrothermal vein where 


J. Seckbach et al. (eds.), Life in the Universe, 239 - 244 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


cyanobacteria would not be expected to live, and (2) 3D-imaging showed that the “filaments” 
form part of much larger, highly irregular structures that do not resemble fossil microbes. 
Going one step fnrther, these anthors conclude that all evidence for life at this period is 
nnfounded and that life probably did not exist at all (Lindsay et al., 2003). Is there any 
reliable evidence for life at this period and what procedures are needed to interpret it? 

2. Early life in 3.S-3.3 Ga rocks from Barberton and the Pilbara 

There is, in fact, abundant evidence for life in the Early Archaean cherts. However, a correct 
understanding of the nature of prokaryote life and biofilm formation, as well as appropriate 
techniques for detailed studies of structures on a micron scale (i.e. electron microscope tech- 
niqnes), are needed. In the first place, previous studies had concentrated on cyanobacteria- 
type microorganisms that are relatively large (generally an order of magnitude larger than 
other types of bacteria) and readily visible in thin sections. Most prokaryotes, however, are 
too small to be easily observed by light microscopy: it is difficult to distinguish a 0.5-1 |JLm 
coccoid from a mineralogical bacteriomorph of the same size in thin section. 


In order to avoid incorrect interpretations, the search for fossil life requires a wide-ranging, 
comprehensive approach. This means observations ranging from the macroscopic, (field 
confexf) fo the microscopic scale (light microscope and electron microscopes), as well as 
chemical and isotopic analyses. There is no single biosignature that can be taken as evidence 
of in situ life in an ancient rock. Below I list the series of steps that I nse in the search for 
fossil prokaryotes. 

1 . Macroscopic study of the field outcrop in order to understand the geological context 
(e.g. water-lain sediments or hydrothermal vein) (Fig. la). Larger-scale structures 
of potential microbial origin can be distinguished, such as tabular and domal stro- 
matolites or thrombolites. 

2. Macroscopic to hand lens investigation of selected samples and cut, fresh surfaces 
of the sample can provide further information relating to the sedimentological 
environment and potential macro-microbial constructions (Fig. lb). 

3. Thin section investigation provides information abont the history of the rock and 
its mineralogical composition. Microfabric textnres that can be important on the 
microbial scale can be studied. Larger-scale microbial structures such as biofilms 
and larger filaments can be identified in fhin section. 

4. Owing to the small size of the majority of prokaryotes, electron microscope inves- 
tigations are necessary for more detailed study of the individual microbes, their 
colonies and their biofilms, keeping frack, however, of fhe subsample location wifh 
respecf to the macroscopic featnres. The SEM study entails delicate sample prepa- 
ration, including HF etching. Artifacts can be prodnced in this process and great 
care needs to be taken to recognise and avoid them. Since a nnmber of minerals, 
notably silica, produce structures that resemble certain microbial shapes, a rigorous 


Figure 1. Volcaniclastic sediments deposited in shallow water conditions from a 3.46 Ga formation in the 
Pilbara: (a Field view, (b) cut surface (detail in (a)) showing truncated ripple marks and pumice fragments, 
suggestive of shallow water conditions. The arrow points to a microbialite horizon. 

list of criteria need to be used in order to make a correct interpretation (see below) 
(Westall, 1999, 2003a; Westall et al., 2000). As noted above, recent contamination 
can also be a problem. 

5. Analytical investigations to comprehend the chemistry of the potential microbes 
and their biofilms can be made through EDS point analysis or elemental mapping 
of selected structures, as well as microprobe studies. Further analysis of selected 
zones for carhon, nitrogen and sulphur isotopes can provide further important 
information, as well as trace element composition. 

There are a number of characteristics relating to microorganisms that can be used in 
the identification of fossil prokaryotes. Whereas modern prokaryotes are identified on fhe 
basis of their (1) morphology, (2) colony-forming behaviour, (3) biochemistry, (4) genetic 
characteristics, of these, only the first two can be used in their entirety for identifying 
fossil prokaryotes. Rapid degradation of the organic molecules changes the biochemical 
and signature and genetic information is lost after some tens of thousands of years. 

The morphological characteristics that can be used in identifying fossil prokaryotes 
include (i) size, (ii) shape, (iii) evidence for cell division, (iv) cell surface texture, which is 
related to (v) cell lysis, (vi) flexibility (for the long rod and filamentous forms) and (vii) cell 
differentiation (a particular characteristic of the cyanobacteria). Additional information can 
be provided by size/shape analysis of the microstructures. 

The colony-forming characteristics include (i) the fact that bacteria are not solitary or- 
ganisms and occur in colonies of a few to millions of individuals, (ii) the very frequent 
association of polysaccharide polymer (extracellular polymeric substances or EPS) asso- 
ciated with the organisms and the colonies, (iii) most colonies consist of more than one 
species forming a consortium, (iv) biofilm formation (biofilms provide a protected habitat in 
which the environmental conditions can be controlled by the microorganisms themselves), 
(v) the inclusion of gas pockets and gas escape structures in thick biofilms, and (vi) fhe 
inclusion of precipifafed or topped minerals in fhe biofilm. 


Figure 2. Microbial mats and fossil microorganisms from >3.4 Ga formations in the Pilbara (a) and Barberton 
(b). (a) Lysed coccoids (e.g. arrow) and degraded EPS in a biofilm formed under shallow water conditions, 
(b) Thick, robust, subaerial biofilm formed of fine filaments (arrow in inset) embedded by thick EPS. Note 
evaporite mineral associated with the biofilm (arrow in main photograph). 


On the basis of the criteria outlined above, I have identified microbial mats formed in differ- 
ent environments by a variety of microorganisms in 3. 5-3. 3 Ga-old cherts from Barberton 
(South Africa) and the Pilbara (Australia) (Westall et ah, 2001, 2002; Westall, 2003a, b) 
{N.B. Walsh (1992) and Walsh and Lowe (1999) have also previously described microbial 
filaments and mats from Barberton). Fine, laminar mats, formed by a consortia of small 
(0.5 |xm) and larger (0.8 |xm) coccoids and small filaments (0.25 |Jtm diameter and up to tens 
of |xm in length), associated with a fine film of EPS, occur at the surfaces of volcaniclas- 
tic sediments deposited in shallow water conditions (Fig. 2a). A laterally-extensive (over 
several meters), mini-stromatolite/thrombolite association occurs at the surface of shallow 
water sediments in one location (Fig. lb). It consists of a consortium of small (0.5 pim) 
and larger (0.8 p.m) coccoids forming a partly columnar to partly clotted fabric. Microbial 
mats also occur in partly subaerial environments, such as the littoral (beach) environment 
(Fig. 2b). Since these mats are exposed to the air, they exhibit a more robust appearance, 
being far thicker than their subaqueous counterparts. They have a dessicated appearance and 
evaporite minerals occur embedded in them, indicating subaerial exposure in an evaporitic 
environment. These mats are formed by small filamentous organisms (0.25 |JLm diameter 
and up to tens of |jLm in length). Other mats formed in the same environment consist of 
vibroid-shaped organisms (2-3.8 pim in length and 1 pim in width) embedded in EPS. Al- 
though all the mats and biofilms observed were formed in either a shallow water or littoral 
environment, there is no morphological evidence for organisms having the characteristics 
of cyanobacteria. 

A preliminary study of a number of rock samples from different stratigraphic horizons 
and different locations within the two Early Archaean greenstone belts indicates that biofilm 
or microbial mat formation at sediment surfaces was relatively common in shallow water 
to subaerial environments (see also Walsh and Lowe, 1999). 


3. Conclusions 

Despite the problems associated with the identihcation of life in the Early Archaean period, 
it is possible to identify ancient fossil life in the cherts from Barberton and the Pilbara, if 
ALL information ranging from the macroscopic down to the microscopic level, as well as the 
biogeochemical analyses, is taken into account, and if care is taken concerning the possible 
presence of recent contamination and/or the production of artifacts during preparations for 
SEM observation. 

Using these methods, I have identified microbial mats on the surfaces of volcaniclastic 
sediments deposited in shallow water to subaerial environments. These mats were formed 
by coccoidal, filamentous and vibroid- shaped organisms, often associated in consortia con- 
sisting of more than one type of organism. Life was common in the Early Archaean. 

4. References 

Brasier, M.D., Green, O.R., Jephcoat, A.P., Kleppe, A.K., van Kranendonk, M., Lindsay, J.F., Steele, A. and 
Grassineau, N. (2002) Questioning the evidence for Earth’s oldest fossils. Nature, 416, 76-81. 

Lepland, A., Arrhenius, G. and Cornell, D. (2002) Apatite in early Archean Isua supracrustal rocks, southern West 
Greenland: its origin, association with graphite and potential as a biomarker. Precambrian Res., 118, 221-241. 

Lindsay J.F., Brasier M.D., McLoughlin N., Green O.R., Fogel M., McNamara K.M., Steele A. and Mertzman, 
S. A. (2003) Abiotic earth - establishing a baseline for earliest life, data from the Archaean of western Australia. 
LPSC XXXIV,# 1137. 

Mojzsis, S.J., Arrhenius, G., McKeegan, K.D., Harrison, T.M., Nutman, A.P. and Friend, C.R.L. (1996) Evidence 
for life on Earth before 3800 millio-n years ago. Nature, 384, 55-59. 

Pflug, H.D. (1979) Archean fossil finds resembling yeasts. Geol. PalaeontoL, 13, 1-8. 

Pflug, H.D., (2001) Earliest organic evolution. Essay to the memory of Bartholomew Nagy. Precamb. Res., 106,79- 

Pflug, H.D. and Jaeschke-Boyer, H. (1979) Combined structural and chemical analysis of 3,800-Myr-old micro- 
fossils. Nature, 280, 483^86. 

Robbins, E.I. (1987) Ap/?^/^//a/^rn/^ra, a possible new iron-coated microfossil in the Isua Iron-Formation, South- 
western Greenland. In: P.W.U. Appel and G.L. LaBerge (eds.) Precambrian Iron Formations, Theophrastes, 
Athens, pp. 141-154. 

Robbins, E.I. and Iberall, A.S. (1991) Mineral remains of early life on Earth? On Mars? Geomicrobiol. J., 9, 

Rosing M.T. (1999) 13C depleted carbon microparticles in >3700 Ma seafloor sedimentary rocks from West 
Greenland. Science, 283, 674-676. 

Schidlowski, M. (2001) Carbon isotopes as biogeochemical recorders of life over 3.8 Ga of Earth history: evolution 
of a concept. Precambrian Res., 106, 117—134. 

Schopf, J.W. (1993) Microfossils of the Early Archean Apex Chert: new evidence of the antiquity of life. Science, 
260, 640-646. 

Van Zuilen, M., Lepland, A. and Arrhenius, G. 2002. Reassessing the evidence for the earliest traces of life. Nature, 
418, 627-630. 

Van Zuilen, M.A., Lepland, A., Teranes, J., Finarelli, J., Wahlen, M. and Arrhenius, G. (2003) Graphite and 
carbonates in the 3.8 Ga old Isua Supracrustal Belt, southern West Greenland. Precambrian Res., 126, 331- 

Walsh, M.M. (1992) Microfossils and possible microfossils from the Early Archean Onverwacht Group, Barberton 
Mountain Land, South Africa. Precambrian Res., 54, 271-293. 

Walsh, M.M. and Lowe, D.R. (1999) Modes of accumulation of carbonaceous matter in the early Archaean: 
A petrographic and geochemical study of carbonaceous cherts from the Swaziland Supergroup. In: D. R. 
Lowe and G.R. Byerly (eds.) Geologic evolution of the Barberton greenstone belt, South Africa, Geol. Soc. 
Am Spec. Paper, 329, 115-132. 

Westall, F. (1999) The nature of fossil bacteria. J. Geophys. Res., 104: 16,437-16,451. 

Westall, F. (2003a) The geological context for the origin of life and the mineral signatures of fossil life. In: 
H. Martin, M. Gardaud, G. Reisse, and B. Barbier (eds.) The Early Earth and the Origin of Life, Springer, 
Berlin, in press. 


Westall, F. (2003b) Stephen Jay Gould, les procaryotes et leur evolution dans le contexte geologique. Palevol, in 

Westall, F., and Folk, R.L. (2003) Exogenous carbonaceous microstructures in Early Archaean cherts and BIFs 
from the Isua greenstone belt: Implications for the search for life in ancient rocks. Precambrian Res., 126, 

Westall, F., De Wit, M.J., Dann, J., Van Der Gaast., S., De Ronde., C. and Gemeke., D. (2001) Early Archaean 
fossil bacteria and biofilms in hydrothermally-influenced, shallow water sediments, Barberton greenstone 
belt. South Africa. Precambrian Res., 106, 93-116. 

Westall, F., Steele, A., Toporski, J. Walsh, M., Allen, C., Guidry, S., Gibson, E., Mckay, D. and Chafetz, H. (2000) 
Polymeric substances and biofilms as biomarkers in terrestrial materials: Implications for extraterrestrial 
materials. J. Geophys. Res., 105, 24,511-24,527. 

Westall, F., Brack, A., Barbier, B., Bertrand, M. and Chabin, A. (2002) Early Earth and early life: an extreme 
environment and extremophiles - application to the search for life on Mars. Proceedings of the Second European 
Workshop on Exo/Astrobiology Graz, Austria, 16-19 September 2002 (ESA SP-518), pp. 131-136. 



Wadia Institute of Himalayan Geology, Dehradun-248001 , Uttaranchal, 
India and The Abdus Salam International Centre for Theoretical Physics 
34136, Trieste, Italy 

Abstract. The comets, meteorites and asteroids have collided with the Earth throughout ge- 
ological history. The mass extinction at Permian-Triassic boundary and Cretaceous-Tertiary 
boundary is strongly supported by the extraterrestrial asteroidal impact theory in the Indian 
Himalayan sequences well exposed at Spiti in Western Himalaya and Um Sohryngkew section 
in Meghalaya, northeastern Himalaya. The carbon isotopic and palaeobiological events suggest 
extraterrestrial impacts at P/T and K/T boundaries all over the world. The early evolution of 
life, its diversification, carbon isotope chemostratigraphy, amino stratigraphy and extinction 
events have been discussed from the Indian Himalaya. 

1. Introduction 

The end of the Cretaceous period is named as K/T boundary and this boundary is marked 
by a catastrophic impact in the Yucatan Peninsula, Mexico. The Chicxulub impact crater is 
a possible trigger for the mass extinction that occured at K/T bondary about 65 million 
years ago in which the dinosaurs perished. The high concentration of platinum group 
elements particularly iridium at the K/T boundary in the Gubbio section of Italy strongly 
supports an extraterrestrial impact (Alvarez et al., 1980). The platinum group elements have 
a rich concentration in extraterrestrial materials like meteorite, asteroid or comet and a very 
low concentration in the terrestrial volcanic eruptions for example Deccan basalt in India 
(Bhandari, 1991). The K/T boundary section at Um Sohryngkew River section (Figure 1) 
in Meghalaya, eastern lesser Himalaya, India contains a strong narrow peak of iridium 
(12.1 ng g). The iridium is enriched by a factor of about 10 in the broad band and by 
a factor of about 500 in the sharp peak above the Cretaceous Shales (Ir = 0.02 ng g, 
Bhandari, 1991). The K/T boundary sections at Padriciano, Trieste in North Italy and 
Slovenia has been established on the basis of palaentological extinction, sedimentological 
facies changes, carbon isotopic variations, iridium anomaly and micro tektites of extrater- 
restrial origin (Pugliese and Drobne 1995; Drobne et al., 1996; Hansen 1995; Ogorelec 
et al., 1995; Gregoric et al., 1998 and Pugliese and Tewari, 2003). The iridium anomaly in 
Meghalaya of India is identical to that found globally and is extraterr-estrial. The Permo- 
Triassic boundary represents the major mass extinction on Earth. During the Permian pe- 
riod Siberia collided with the other landmasses and the largest super continent Pangea 


J. Seckbach et al. (eds.), Life in the Universe, 245 - 248 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. Geological and location map of the K/T boundary section, Meghalaya, NE Lesser Himalaya, India. 

was created. The southern continent Gondwana started to drift away to the north creating 
new microcontinents. The Permo-Triassic boundary is characterized by Siberian volcan- 
ism, palaeoclimatic changes, oceanic anoxia events and extraterrestrial impacts. The recent 
carbon isotopic excursions from the P/T boundary sections of the Spiti valley in Tethys 
Himalaya of India has supported the impact hypothesis (Ghosh et al. 2002). In the present 
paper the major extinction events of life since the origin of life on Earth has been discussed. 

2. Origins of Life from Amino Acids in Meteorites to Stromatolites 

According to the recent research (Oro et al. 1971; Tewari, 2001a, 2002 a,b) comets and 
meteorites may have been a source of organic compounds on the early Earth. The Murchison 
meteorite found in Australia contains amino acids glycine, alanine, valine, proline, aspartic 
acid and glutamic acid (Oro et al. 1971). The discovery of amino acids phenylalanine, 
tyrosine and tryptophan by Laser Raman Spectroscopy from 4.5 billion year old Didwana- 
Rajod meteorite from Rajasthan, India (Tewari, 2002 a, b) confirms that life might have 
originated in space before being introduced to Earth by meteorites. The most convincing 
evidence for the extraterrestrial delivery of amino acids (alpha amino isobutyric acid and 


racemic isovaline) comes from the Cretaceous-Tertiary boundary section of the Stevens 
Klint in Denmark. The oldest sedimentary rocks on Earth are 3.9 billion years old Isua meta- 
Quartzite in Greenland but no convincing microfossils have been reported from these rocks. 
The oldest record of life on Earth, in the form of bacterial microfossils and stromatolites, is 
reported from the Apex chert of Western Australia (Schopf, 1993). The early evolution and 
diversification of life on Earth with special reference to the Himalaya has been discussed 
by Tewari (2001a, 2003 in press). 

3. Discussion and Conclusion Major Extinction Events of Life on Earth 

The stromatolites of Mesoproterozoic age (large Conophytons and other columnar forms) 
declined around 650 Ma. in Neoproterozoic period before the Ediacaran explosion of 
metazoans and metaphytes. The Ediacaran explosion of metazoan and metaphyte mul- 
ticellular life took place after Neoproterozoic palaeoclimatic change from snow ball 
Earth to global warming (Tewari, 2001b). A major global decline of Mesoproterozoic 
stromatolites and planktonic acritarchs has been recorded on Earth related to Neopro- 
terozoicWarangian/Blainian glacial event. Explosive radiation of new acanthomorphic 
acritarchs, sponge spicules, multicellular brown sheet algae Vendotaenids and Ediacaran 
metazoans were recorded from Australia, Krol Group of the Uttaranchal Lesser Himalaya, 
India, China, Siberia, Canada and Namibia in South Africa (Tewari, 2001, 2003). During 
the Vendian 650 Ma. ago the dominant Precambrian flora and fauna perished in the first 
great extinction and has been correlated with a large glaciaton event. The Cambrian period 
is marked as an important turning point in the history of evolution of life on Earth. This is 
the time when most of the major groups of animals first appeared in the fossil record. This 
event is called the Cambrian Explosion of life on Earth. During the Cambrian, the trilo- 
bite Olenellids and archaeocyathids (reef building organisms) perished. Palaeobiological 
records also suggest that climate during Permocarboniferous was cool in Gondwanaland. 
The Cretaceous period about 65 Ma. ago suffered an asteroid impact and caused global 
cooling on Earth and extinction of dinosaurs from the planet. The organic compounds such 
as amino acids of extraterrestrial origin have been found in Martian (SNC) and other mete- 
orites landing on Earth from the asteroid belt between Mars and Jupiter strongly suggests 
that the meteorites braught life to the Earth and can cause its extinction. Astrobiology in 
future may give us important clues regarding extraterrestrial origin of life on Earth and 
other planets of the universe (Tewari, 1998). 

4. Acknowledgements 

The author is grateful to Professor Julian Chela Elores, Abdus Salam International Cen- 
tre for Theoretical Physics, Trieste, Italy for encouragement. Professor Nevio Pugliese of 
Dipartimento di Scienze Geologiche Ambientali e Marine, Trieste, Italy is thanked for 
kindly reviewing the article and valuable suggestions. Professor Joseph Seckbach, Hebrew 
University, Jerusalam, Israel is thanked for improving the article. The Directors of the 
Wadia Institute of Himalayan Geology, Dehradun, India and A.S. International Centre for 
Theoretical Physics, Trieste, Italy are thanked for providing facilities. 


5. References 

Alvarez, L.W., Alvaerz, W.F., Asaro, F. and Michel, H.V. (1980) Extraterrestrial cause for the Cretaceous-Tertiary 
extinction. Science, 208, 1095-1100. 

Bhandari, N. ( 199 1 ) Collisons with Earth over geologic times and their consequences to the terrestrial Environment. 
Current Sci. 61, 97-103. 

Brazazatti, T., Caffau, M., Cozzi, F., Drobne, K. and Pugliese, N. (1996) Padriciano Section (Karstof Trieste, 
Italy). In: K. Drobne and B. Goriean (eds.) International Workshop POSTOJNA 96 The role of impact 
processes in the geological and biological evolutionof Planet Earth, pp. 189-198. 

Drobne, K., Ogorelec, B., Dolenec, T, Marton, E. and Pugliese N. (1996) Cretaceous-Tertiary boundaryon the 
carbonate platform of the NW part of the Adriatic Plate. In: N. Bardet and E. Buffetaut (eds.) Seance spec. 
Soc. Geol. France La Limite Cretace-Tertiare: aspects biologiques et geologiques, Resume. 

Ghosh, P, Bhattacharya, S.K., Shukla, A.D., Shukla, P.N., Bhandari, N., Parthasarathy, G. and Kunwar, A.C. 
(2002) Negative, D., 13 C excursion at the Permo-Triassic boundary in the Tethys. sea, Curr. Science. 83, 

Hansen, H.J., Drobne, K., Gwozdz, R. (1995) The K/T boundary in Slovenia: dating by magnetic susceptibility, 
stratigraphy and ridium anomaly in a debris flow In: A. Montari and C. Coccioni (eds.) ESF 4th International 
Workshop, 84-85, Anacona. 

Ogorelec, B., Dolence T, Cucchi, F., Giacomich, R., Drobne, K. and Pugliese, N. (1995) Sedimentological and 
geochemical characteristics of carbonate rocks from the K/T boundary to Lower Eocene in the Karst area 
(NW Adriatic Platform) 1st Croatian Geological Congress Opatija, Zbomik radova Proceed., 2, 415—421. 

Oro, J., Gilbert, J., Lich tenstein, H., Wikstorm, S. An Flory, D.A. (1971) Amino acids, aliphatic and aromatic 
hydrocarbons in the Murchison meteorite. Nature, 230, 105-106. 

Pugliese, N. and Drobne, K. (1995) Palaeontological and palaeoenvironmental events at the K/T boundary in the 
Karst area. In: Montari, A. and Coccioni, R (eds.) ESF 4th International Workshop. 137—140. 

Pugliese, N. and Tewari, V.C. (2003) Peritidal sedimentary depositional facies and preliminary carbon Isotope 
data from K/T boundary carbonates at Padriciano, Trieste, Italy. In: 32nd International Geological Congress, 
Italy to be held in Florence from August 20-28, 2004 (abstract). 

Schopf, J.W. (1993) Microfossils of the Early Archaean Apex Chert New evidence of the Antiquity of life. Science, 
260, 640-646. 

Tewari, V.C. (1998) Earliest microbes on Earth and possible occurrence of stromatolites on Mars. In: J. Chela 
Flores and R. Raulin (eds.) Exobiology Matter, Energy and Information in the Origin and Evolution of Life 
in the Universe. Kluwer Academic Publishers, Netherlands, pp. 261—265. 

Tewari, V.C. (2001a) Origins of life in the universe and earliest prokaryotic microorganisms on Earth. In: J. Chela 
Flores, T. Owen and F. Raulin (eds.) First Steps in the Origin of Life in the Universe, Kluwer Publishers, the 
Netherlands, pp. 251-254. 

Tewari, V.C. (2001b) Neoproterozoic glaciation in the Uttaranchal Lesser Himalaya and the global Palaeoclimate 
change. In National Symposium on Role of Earth Scientists in Integrated Development and Related Societal 
Issues. GSI Spl. Publ., 65, 49-55. 

Tewari, V.C. (2002a) Discovery of amino acids from Didwana-Rajod meteorite and its implication on Origin of 
Life. Journal of Geological Society of India, 60, 107-1 10. 

Tewari, V.C. (2002b) Might life on Earth come from space. Nature News India, 2002, 11. 

Tewari, V.C. (2003) Proterozoic diversity in Microbial life of the Himalaya. In: J. Seckbach (ed.) Origins Genesis, 
Evolution and Biodiversity of Microbial Life in the Universe. Kluwer Academic Publishers (in press). 



Wadia Institute of Himalayan Geology, Dehradun-248001 , Uttaranchal, 
India and The Abdus Salam International Centre for Theoretical Physics 
34136, Trieste, Italy 

Abstract. The Mesoproterozoic (Riphean) stromatolite taxa are recorded from the Buxa 
Dolomite of the Ranjit Window, Sikkim Lesser Himalaya, India. The Riphean character- 
istic taxa are Omachtenia, Colonnella columnaris, Kussiella kussiensis, Conophyton cylin- 
dricus, C. garganicum, Rahaella elontgata Tewari, Jacutophyton, Baicalia nova, Tungussia, 
Jurusania, Inzeria, Gymnosolen, Minjaria, Stratifera, and Gongylina. The Neoproterozoic- 
Terminal Proterozoic (Vendian) stromatolite assemblage Paniscollenia, Aldania, Tungussia, 
Linella, Colleniella, Linocollenia, Boxonia, linked Conophyton, Conistratifera, microstroma- 
tolites, Stratifera, Irregularia, Nucleella, digitate stromatolites and oncolites are well developed 
in the Buxa Dolomite, Ranjit Window, Sikkim and its equivalents (Menga Limestone, Dedza 
Limestone and Chillipam Limestone) in the adjoining Arunachal and Bhutan Lesser Himalaya. 
The Mesoproterozoic to Terminal Proterozoic stromatolite diversification has been recorded for 
the first time from the Buxa Dolomite of the Sikkim Lesser Himalaya, India. The palaeobiolog- 
ical and biosedimentological significance of the stromatolites in the Buxa Dolomite has been 

I. Introduction 

The Buxa Group in the Northeastern Lesser Himalaya, India is well represented 
by dolomites, limestones, cherty stromatolitic-oolitic-intraclastic dolomite, calcareous 
quartzite and black carbonaceous shales in Arunachal and Sikkim areas (Acharyya, 1974; 
Tewari, 2001, 2002, 2003). The stromatolitic dolomite sequence is 800 m. thick in the Ranjit 
Window section of the Sikkim Lesser Himalaya. 

The distribution of stromatolite assemblages, morphological variations and the 
palaeoenvironment of deposition has been established. The detailed study of the stromato- 
lite morphology, microstructure, microfabrics and associated microbiota in the stromatolitic 
and bedded cherts suggests a Lower Riphean to Terminal Proterozoic age for the Buxa 
Dolomite in the Sikkim Lesser Himalaya. Tewari (2003) has done integrated sedimentolog- 
ical, palaeobiological, carbon and oxygen isotopic and Laser Raman Spectroscopic studies 
of the Buxa Dolomite from Arunachal Lesser Himalaya and has suggested a Neoproterozoic 
to Pre Cambrian — Cambrian boundary transition in the eastern lesser Himalaya. 


J. Seckbach et al. (eds.), Life in the Universe, 249 - 250 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Palaeobiology and Biosedimentology of the Buxa Dolomite 

Palaebiological remains discovered from the petrographic thin sections of the black cherts 
associated with the stromatolitic dolomites of the Buxa Group in Ranjit Window, Sikkim are 
organic walled microfossils {Leiosphaeridia, Obruchevella, Myxococcoides, Siphonophy- 
cus, Eomycetopsis, Micrhystridium, and Acanthomorphic acritarchs). The sedimentolog- 
ical studies of the stromatolites and sedimentary structures suggest that Buxa Dolomite was 
deposited in intertidal to subtidal, sandy intertidal and lagoonal environment The carhon 
and oxygen isotope analysis of the Buxa Dolomite from the Ranjit Window shows that 
carbon isotope ratios (8^^C) vary from —1.4 to +1.0 (PDB) and oxygen isotope values 
(S'^O) range from 18.9 to 23.9 (SMOW). The isotopic data also supports a shallow marine 
depositional environment. The geochemical analysis of stromatolitic carbonates has shown 
16 to 22% MgO and 14 to 31% CaO. Laser Raman Spectra has shown the shift in wave 
number at 1 100 cm and confirms the presence of amino acids (biomolecules). 

3. Acknowledgements 

The author is grateful to Professor Julian Chela Flores, ICTP, Trieste, Italy and Dr. F. 
Westall, CBM, CNRS, Orleans, France for discussions. I am indebted to Prof. Joseph 
Seckbach, Hebrew University, Jerusalam, Israel for reviewing the article and valuable sug- 
gestions. The Directors of the Wadia Institute of Himalayan Geology, Dehradun, India and 
Abdus Salam International Centre for Theoretical Physics, Trieste, Italy are thanked for 
providing facilities. The financial assistance from the D.S.T. for the project Palaeobiology 
and Biosedimentology of the Buxa Dolomite, NE Lesser Himalaya (No.SR/S4/ES-0) is 
thankfully acknowledged. 

4. References 

Acharyya, S .K. ( 1 974) Stratigraphy and sedimentation of the Buxa Group, Eastern Himalaya. Himalayan Geology 
4 , 102-116. 

Tewari, V.C. (2001) Discovery and sedimentology of microstromatolites from Menga Limestone (Neoprotero- 
zoicA^endian), Upper Subansiri District, Arunachal Pradesh, NE Himalaya, India. Current Science 80 , 1440- 

Tewari, V.C. (2002) Lesser Himalayan stratigraphy, sedimentation and correlation from Uttaranchal to Arunachal. 
Aspects of Geology and Environment of the Himalaya. Gyanodaya Prakashan, Nainital. pp. 63—88. 

Tewari, V.C. (2003) Sedimentology, palaeobiology and stable isotope chemostratigraphy of the Terminal Pro- 
terozoic Buxa Dolomite, Arunachal Pradesh, NE Lesser Himalaya. Journal of Himalayan Geology 25 , ( 1 ), 

X. Searching for Extraterrestrial Life, 
Europa, Titan and Extrasolar Planets 



Institute for Astronomy, University of Hawaii 
2680 Woodlawn Drive, Honolulu, Hawaii 96822 USA 

1 . Introduction 

The search for life outside the Earth is currently stuck in the same debate that once sur- 
rounded the quest for other planetary systems. Excellent scientists support a spectrum of 
views ranging from a strong sense that life is such an improbable state of matter that life on 
Earth is probably all the life there is, through grudging admission that there may be other 
planets inhabited by colonies of bacteria, to the idea that millions of technically advanced 
civilizations are contemplating this same question throughout the Galaxy (Goldsmith and 
Owen, 2002). 

By chance we happen to live in the era when, for the first time, we can transform this 
fascinating speculation into an experimental science: we can actually go out and look for 
signs of extraterrestrial life. 

What are those signs? Life on Earth may not be the only life in the universe, but it is the 
only life we know. Hence we must start with a consideration of life as we know it, attempting 
to generalize from its most basic characteristics to find constraints that environments must 
satisfy to be habitable and then to identify the observable effects of living systems on 
those environments. As we are in no position to travel to extra-solar planets, the effects 
we seek are essentially confined to changes in atmospheric composition that we can detect 
spectroscopically from our remote vantage point. Eor example, the fact that our atmosphere 
is 21% oxygen would be a sure indication of life on Earth to an alien spectroscopist on the 
other side of the Galaxy (Owen 1980). Without the green plants to keep producing it, our 
present supply of oxygen would disappear in several million years, just 0.1% of geological 

Looking into the fundamental chemistry of life, we are struck by its dependence on 
carbon as the main compound-forming element and water as the essential solvent. All life 
depends on carbon, and everywhere on Earth we find water there is life. The only places 
on our planet that are sterile are marked by the absence of this essential substance. A quick 
examination of the properties of carbon and water suggests that life’s dependence on them 
is not the product of random chance. 

Both carbon and water are extremely common in the universe. Water is one of the best 
solvents we know; its high heat capacity and latent heat of vaporization make it a good 
temperature regulator; it is an excellent greenhouse gas, ice floats so life can “winter over,’’ 


J. Seckbach et al. (eds.), Life in the Universe, 253 - 256 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


etc., etc. Carbon is the most versatile of all the elements in forming the complex molecules 
that will be essential for any form of life to store and transmit both energy and information. 
It moves easily between the most oxidized form, CO2 and the most reduced form, CH4, and 
both of these end members are excellent greenhouse gases, etc., etc. 

We conclude that life on other worlds is highly likely to use carbon and water, while 
nitrogen’s cosmic abundance suggests it will also be a component of other living systems 
just as it is on Earth. We are not being overly restrictive with this conclusion because we 
don’t expect life elsewhere to use the same compounds of C, H, N, and O as we find on 
Earth. We don’t expect the same amino acids, proteins, DNA, RNA, etc. It’s not going to 
look like us and could well be inedible and smell terrible, but life elsewhere will probably 
rely on carbon as its main structural element, and water as its solvent, and incorporate 
nitrogen in its compounds. So where will we find it? 

2. “Had We But World Enough and Time . . 

Andrew Marvell was talking about love when he wrote that line, but it applies as well to 
life. We need a planet to provide the habitat for life, and we need the global climate on that 
planet to be reasonably stable for at least 4.6 billion years if we hope for intelligent life. We 
also need a long-lasting source of energy — thermal, chemical, or best of all, starlight. 

These requirements and desiderata translate to the need for an Earth-like planet in a 
nearly circular orbit at the appropriate distance from a Sun-like star. The deeper requirement 
is to allow liquid water to exist on the planet’s surface, which translates to a range of distances 
that define an annulus around the star (actually the space between two concentric spheres) 
known as the star’s habitable zone. Stars slowly get hotter with time, so the habitable zone 
gradually moves outward. Eurthermore, the temperature of a planet will also depend on the 
composition of its atmosphere: how much of a greenhouse effect it can produce. Thus the 
outer boundary of the habitable zone is not sharply defined. 

In our own solar system, Venus (at 0.72 AU) is outside the habitable zone. It is too close 
to the Sun for water to be stable on its surface. Instead, a runaway greenhouse effect caused 
any original oceans to boil, and the resulting overheated atmosphere allowed water vapor 
to reach altitudes where it was easily dissociated by ultraviolet photons from the Sun. The 
hydrogen escaped, leading to a 150 times enrichment of D/H on the planet, which has been 
observed (Donahue et al., 1982; de Bergh et al., 1991). 

On the other hand. Mars (at 1.5 AU) is still within the zone. The problem for Mars is 
not that it’s too far from the Sun; instead, it is too small to sustain the thick atmosphere that 
would provide the necessary greenhouse effect to keep it warm. Asteroidal bombardment 
would remove more than 100 times the present mass of the atmosphere, unhindered by the 
planet’s weak gravitational field (Melosh and Vickery 1989). An Earth-size planet in the 
orbit of Mars could be habitable. 

Even the present Mars may have harbored the origin of life early in its history during 
an episode when the atmosphere was thicker and liquid water ran across the surface and 
pooled in its impact craters (Owen, 1997). Just how warm and wet Mars was in that early 
time and how long the periods of temperate climate lasted are still hotly debated (Squyres 
and Kasting, 1994; Eorget and Pierrehumbert, 1997; Owen and Bar-Nun, 2000). At this 
stage in our ignorance we can even hold out the hope that life evolved to forms that survived 


in warm, wet regions underground on Mars, just as life has done on Earth (Onstott et ah, 
1999). The discovery that liquid water may still erupt from time to time onto the Martian 
surface (Malin and Edgett, 2000) adds to this hope. 

A less likely but still intriguing target is offered by Jupiter’s icy satellite Europa. This 
moon is warmed from the inside by the dissipation of tidal energy from Jupiter, the same 
engine that drives the astonishing volcanic activity on the inner satellite lo. Here the thought 
is that beneath the icy crust of Europa there may be a warm ocean of water, and in that 
ocean there could be life (Gaidos et al., 1999). 

3. Finding Life on Brave New Worlds 

What about all those other worlds out there of whose existence we now know? The sad fact 
is that all of these super-giant planets are themselves totally unsuited to be abodes of life. 
Not only that, most of them have migrated through the habitable zones of their systems to 
their present positions, thereby wiping out any Earth-like planets that might have existed. 
The other giants occupy eccentric orbits that will again cause them to wreak havoc on the 
types of planets we seek, or prevent them from forming in the first place. As of 1 October 
2003, we know of only one suitable system. It has a giant planet in a nearly circular orbit at 
a distance of about 3 AU from its star, with no other giants between it and the star. However, 
we could only hope to detect such a system in the last year or so, when the accumulated 
observations would have covered enough of the giant planet’s orbit to make identification 
certain. Thus we may hope for additional discoveries of systems whose basic architecture 
is like our own in the very near future. 

This is reassuring, but we still won’t have the certainty that these systems have Earth- 
size planets in their habitable zones. They have room for such planets, but are the planets 
there? This information will come from the Kepler and Eddington missions, which will 
start returning data on transits of terrestrial planets in 2007. The next step will be the use 
of interferometers in space to separate the light from these planets from the glare of their 
stars, allowing us to do spectroscopy to see what gases their atmospheres contain. 

What gases do we seek? We have seen that plentiful oxygen is a sure sign of life. The 
blue-green bacteria created the first global abundance of oxygen on Earth some 2.5 billion 
years ago, and their descendants are still releasing oxygen today. Similar organisms, as well 
as trees and grasses, could be thriving on Earth-like planets throughout the Galaxy. Other 
bacteria on our own planet also give themselves away by the gases they produce, as the 
2 ppm of methane in our atmosphere testifies. This perspective defines our task: we are 
looking for gases that would not exist in planetary atmospheres if living organisms were 
not present to produce them. 

How can we be absolutely certain that the discovery of a disequilibrium gas in a planetary 
atmosphere is really a sign of life? In fact, there are other ways these gases could be 
generated, but we can eliminate these false positives with proper care. 

Consider oxygen. Huge amounts of this gas will be produced by the runaway green- 
house phenomenon that desiccated Venus. This will be a temporary effect, however, as the 
oxygen liberated by the photolytic destruction of water vapor in a planet’s upper atmosphere 
will soon combine with crustal rocks. By measuring the planet’s temperature from its IR 
spectrum, there would be no doubt about the source of its atmospheric oxygen. 


In the case of methane and other reduced gases, the key parameters will be the size 
of the planet, its distance from its star, and the age of the star. Any inner planet in any 
system throughout the Galaxy will ineluctably convert to a CO 2 -dominated atmosphere if 
life fails to develop. We see this clearly with Mars and Venus in our own system. So if we 
find a significant amount of methane in the atmosphere of a distant Earth-sized planet that 
is in the habitable zone of a star over one billion years old, we can be quite certain that we 
are looking at an inhabited world. The inhabitants may simply be bacteria, but they would 
nevertheless demonstrate that the transformation of nonliving to living matter was not a 
unique event in the Galaxy. 

4. The Future 

All of these possibilities, and surely others as well, will receive detailed scrutiny and elabo- 
ration as we begin to undertake the first direct searches for evidence of life on other worlds 
like ours. The good news is that we have indeed reached the stage in the development of our 
own civilization where spacecraft and radio telescopes are taking the place of speculation in 
our quest to find life elsewhere in the universe. Is living matter a miracle or a commonplace 
phenomenon? By the year 2020 we should surely know. 

5. References 

de Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.-P. and Lutz, B.L. (1991) Deuterium in Venus: Obser- 
vations from Earth. Science 251, 547-549. 

Donahue, T.M., Hoffman, J.H., Hodges, R.R., Jr. and Watson, A.J. (1982) Venus Was Wet: A Measurement of the 
Ratio of D/H. Science 216, 630-633. 

Forget, F. and Pierrehumbert, R.T. (1997) Warming Early Mars with CO 2 Clouds that Scatter Infrared Radiation. 
Science 278, 1273-1276. 

Gaidos, E.J., Nealson, K.H. and Kirshvink, J.L. (1999) Life in Ice-covered Oceans. Science 284, 1631-1633. 
Goldsmith, D. and Owen, T. (2002) The Search for Life in the Universe, 3e, University Science Books, Sausalito, 

Malin, M.C. and Edgett, K.S. (2000) Evidence for Recent Groundwater Seepage and Surface Runoff on Mars. 
Science 288, 2330-2335. 

Melosh, H.J. and Vickery, A.M. (1989) Impact Erosion of the Primordial Atmosphere of Mars. Nature 338 , 

Onstott, T.C., Phelps, T.J., Kieft, T., Colwell, F.S., Balkwill, D.L., Fredrickson, J.K. and Brockmann, F.J. (1999) 
A Global Perspective on the Microbial Abundance and Activity in the Deep Subsurface. In: J. Seckbach (ed.): 
Enigmatic Microorganisms and Life in Extreme Environments. Kluwer Academic Publishers, Dordrecht, The 
Netherlands, pp. 487-500. 

Owen, T. (1980) The Search for Early Forms of Life in Other Planetary Systems: Future Possibilities Afforded 
by Spectroscopic Techniques. In: M. Papagiannis (ed.) Strategies for the Search for Life in the Universe. 
D. Reidel, Dordrecht, The Netherlands, pp. 177-185. 

Owen, T. (1997) Mars: Was There an Ancient Eden? In: C. Cosmovici, S. Bowyer and D. Wertheimer (eds.) 
Astronomical and Biochemical Origins and the Search for Life in the Universe. Editrice Compositori, Bologna, 
Italy, pp. 203-218. 

Owen, T. and Bar-Nun, A. (2000) Volatile Contributions from Icy Planetesimals. In: R. M. Canup and K. Righter 
(eds.) Origin of the Earth and Moon. University of Arizona Press, Tucson, pp. 459^71. 

Squyres, S. W. and Kasting, J. F. (1994) Early Mars: How Warm and How Wet? Science 265, 744-749. 



^INFM, Dipartimento di Fisica E. Fermi, Universita di Pisa, Via 
Buonarroti 2, 1-56127, Pisa, Italy, * Permanent Institute: 

Department of Physics, A.R.S.D College, University of Delhi, 

Dhaula Kuan, New Delhi-110021, India, and ^The Abdus Salam 
International Centre for Theoretical Physics, Trieste, Italy and Institute de 
Estudios Avanzados, Caracas 101 5 A, Venezuela. 

I . Introduction: The Presence of Bacterial Waste and its Consequence 

Of particular interest to the scientific community is the possible existence of extraterrestrial 
biological activity due to the presence of liquid water under the icy surface. This search is 
motivated by analogy with anaerobic life found in abundance in under sea volcanic vents 
on Earth (McCollom 1999; Pappalardo et al, 1999) and the dry valley lakes of Antarctica. 
If Europa does indeed have a liquid water ocean beneath the outer ice crust as a result 
of interior volcanic heating, then it is possible that hydrothermal vents located on the 
seafloor may provide the necessary conditions for simple ecosystems to exist. The water 
ejected from the hydrothermal vents is typically rich in sulfur and other minerals. Bacteria 
present in the water extract all nutrients directly from the sulfur via chemosynthesis, making 
sunlight and oxygen unnecessary. Geochemical models have been proposed to explore the 
possibility that lithoautotropic methanogenesis (CO 2 + 4 H 2 = CH 4 + 2 H 2 O) could be a 
source of metabolically useful chemical energy for the production of biomass at putative 
Europan hydrothermal systems (McCollom, 1999; Delitsky and Lane, 1997). In the absence 
of oxygen, anaerobic decomposition takes place in these hydrothermal vents. As a result of 
putrefactive breakdown of organic material (proteins), some elements are produced, such 
as hydrogen sulfide, methane, ammonia, and mercaptans, which are thiols/thio alcohols 
(RS-H, R-paraffinic, aromatic or cyclopraffine group). The sulfur in mercaptans found in 
bacteria ultimately derives from sulfate (— SO^” ), which is reduced in the cell. In bacteria 
that utilize sulfate as a source of sulfur, several steps in the reduction process eventually 
lead to hydrogen sulfide (H 2 S) which is a direct precursor of the amino acid cysteine which 
is a thiol! The original source of sulphur on the Europan surface may be either: (a) ions 
implanted from the Jovian plasma, or alternatively, (b) much of the sulphurous material 
may be endogenic. The first possibility (a) has the difficulty that implantation would be 
expected to produce a more uniform surface distribution (Carlson et al, 1999). On the other 
hand, sulphurous material on Europa’s surface may have been formed internally and over 
geologic time it could have been emplaced onto the surface either geologically, or as we 


J. Seckbach et al. (eds.), Life in the Universe, 257 - 260 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


argue in this paper by the accumulated effect of biogenic processing over geologic time. 
Interestingly, evidence has been provided for the presence of mercaptans on the surface 
of Europa (McCord et al, 1998), using reflectance spectra returned by the Galileo near 
infrared mapping spectrometer (NIMS) experiment. They found absorption in the 3.88 p,m, 
attributed to S-H bond of mercaptans. A major scientihc question to be answered about the 
possible existence of life is: If biological process such as methanogenesis and putrefaction 
are at work then how do they affect observable or measurable quantities? What would be the 
best way to detect these organisms? In order to answer such questions, lander missions would 
be needed since it seems unlikely that remote sensing techniques such as NIMS alone would 
be sufficient. An ideal approach to detect the presence of life would be to drop penetrating 
probes and an in situ vehicle, which would carry a chemical/physical laboratory (CPL). The 
in situ CPL will perform chemical and physical analysis of ice and ocean water to obtain 
information on the chemical constituents of the ice. Instruments required for these analyses 
would include UV-spectrometer, high frequency ultrasonic analyzers, chemical analyzer to 
look directly for bacterial metabolic wastes or indirect effect of these waste products on the 
icy surface or the water beneath. Interestingly, the use of fermentative products (organics 
and carbon dioxide) as metabolic signatures on Europa has been suggested (Prieur, 2002). 

2. What Kind of Solute-Solvent Interactions We Should Expect 
on Europa’s Surface? 

The presence of various bacterial excreta is expected to perturb the normal water lattice 
as (H20)iiquid _ (H20)quasi-iattice- Release of these excreta over a prolonged period of time 
would certainly change the various physical properties of the icy layer and that of the water 
that lies beneath. The perturbations would be reflected in the various physical properties 
measured such as the viscosity, ultrasonic velocity, ultrasonic absorption coefficient, UV 
absorption spectra etc. UV absorption spectra are quite ideal for monitoring the forma- 
tion/breaking of hydrogen bonds. An enthalpy change of 5-7 kcal/mole is expected during 
the formation/breaking of hydrogen bonds. The most likely hydrogen bond that may be 
formed is between the hydrogen of iodole chromophore and water molecule. The iodole 
chromophore may act as a proton donor in the hydrogen bonding. Low molecular weight 
and high functionality of water plays a significant role in biological processes. Water can 
be assumed to be a two-state system (Pethrick, 1982). Each molecule is joined to its nearest 
neighbors with four links. On the surface of these clusters exist molecules joined by less 
than the maximum number and may be considered to be in the process of either forming or 
breaking the cluster. The total can be divided into two regions, an open low density arrange- 
ment where the molecules are extensively hydrogen bonded and a high density region where 
the molecules are non-bonded. The equilibrium may be described as: (H20)iiquid (bound) n 
(H 2 O) (free monomeric). Solute molecules (bacterial waste) which have the ability to form 
hydrogen bonds will attack the low density region and may act as acceptors and compete 
with the protons for the lone pair of electrons. The net result of such interaction is the 
disruption of the low density region and the equilibrium shifts towards the non-bonded 
form with a consequent increase in the density. Such a transition will change the freezing 
point of water and can be measured using high frequency ultrasonic transducers. Increase 
in solute concentration (bacterial waste) over a prolonged period of time is expected to 


produce an enthalpy change of 1-2 kcal/mole. This will be reflected as a red shift in some 
standard UV spectral lines. This happens because of the “Franck-Condon’s “strain and 
the “Polarization shift” (Chaudhury et ai, 1994). The importance of experiments to detect 
bacterial wastes including mercaptans, that NIMS has demonstrated to be present on the 
Europan surface must be realized because non-living sources of mercaptans are difficult to 

3. Discussion and Conclusions 

The detection and characterization of any bacterial excreta is an integral part of our search for 
evidence of life on Europa. In order to achieve this goal, it will be necessary to embark on an 
extensive survey of the surface of Europa using lander missions. Clearly an ideal approach to 
obtaining information on the composition of the European “ocean” is to sample the surface 
material which is thought to have originated at depth and become distributed on the surface 
by eruption like processes. 

Any point on the surface of Europa which exhibits properties typical of contamination by 
bacterial waste should serve as a window to the underlying ocean. Before embarking upon 
any ambitious project, it would be helpful if we could test this proposal in the laboratory 
by mimicking the surface of Europa. This could be done by allowing for bacteria to grow 
for a prolonged period in an artificial pond and then freezing the water. Subsequently one 
can measure the various physical and chemical properties on the surface of this pond. This 
will help to understand what we should expect on the surface of Europa. However, in this 
context we should point out that such an experiment is probably mimicked by nature in the 
dry valley lakes of southern Victoria Land of Antarctica (Doran et al, 1994; Parker et ai, 
1982). These lakes lie in an ice-free area of just under 5000 km^ . This area contains more than 
20 permanent lakes, which are warm environments containing liquid water that may reach 
room temperature under their iced surface of 4-6 m, while the outside temperature remains 
well below zero degrees Celsius. In the dry valley lakes there are abundant microorganisms 
underneath their iced surface. The estimated annual S removal is 104 kg in Lake Chad 
[cf.. Table 5 in (Parker et ai, 1982)]. At any given time an important characteristic of the 
anaerobic prostrate cyanobacterial mats of, for instance Lakes Fryxell and Hoare, is their 
appearance as black mats, coarse and with a distinct H 2 S odor (Doran et al., 1994). Thus, 
at any given moment endogenic sulphur and other elements are to be found on the iced 
surface of, for instance. Lake Chad. To the best of our knowledge, there is no information 
on the presence of mercaptans in the dry valley lakes of Antarctica. Further investigations 
are required to search for mercaptans (or other bacterial wastes) in these dry valley lakes. 
There is, therefore, a suggestive analogy between the chemical composition of the surface 
of the dry valley lakes with the presence of sulfur compounds (such as mercaptans) on the 
iced surface of Europa. 

4. Acknowledgements 

A. Bhattacherjee acknowledges support by the Abdus Salam International Centre for 
Theoretical Physics, Trieste, Italy under the ICTP-TRIL fellowship scheme. 


5. References 

Carlson, R. W., Johnson, R. E. and Anderson, M. S. (1999) Sulfuric acid on Europa and the radiolytic sulfur cycle, 
Science, Vol. 286, pp. 97-99. 

Chaudhury, K., Bhattacherjee, A., Bajaj, M.M. and Jain, D.C. (1994) An analysis of 5-(p-Hydroxyphenyl)-5- 
phenylhydantoin induced perturbations in the 200^00 nm region. Revue Roumaine de Chimie, Vol. 39 , 
pp. 1091-1098. 

Chela-Flores, J. (1998a) Europa: A potential source of parallel evolution for microorganisms. In: Instruments, 
Methods and Missions for Astrobiology. The International Society for Optical Engineering, Bellingham, Wash- 
ington USA (R.B. Hoover, ed.), Proc. SPIE, Vol. 3441 , pp. 55-66; 

Chela-Flores, J. (1998b) A search for extraterrestrial eukaryotes, Physical and Biochemical Aspects of Exobiology, 
Origins LifeEvol. Biosphere,Yo\. 28 , 583-596; 

Chela-Flores, J. (2003). Testing Evolutionary Convergence on Europa. International Journal of Astrobiology 
(Cambridge University Press), in press, 

Delitsky Mona L. and Lane, Arthur L. (1997) Chemical schemes for surface modification of icy satellites: A road 
map. Jour. Geochem. Res., Vol. 102 , No. E7, pp. 16, 385. 

Delitsky, L. and Lane, A. L. (1998) Ice chemistry in Galilean satellites Jour. Geophys. Res. Vol. 103 , pp. 31,391- 

Doran, P.T., Wharton, Jr., R.A. and Berry, Lyons, W (1994) Paleolimnology of the McMurdo Dry Valleys, 
Antarctica , J. Paleolimnology 10 , pp. 85-1 14. 

Greenberg, R. (2002), Tides and the biosphere of Europa, American Scientist, Vol. 90 , pp. 48-55. 

Horvath, J. Carsey, F, Cutts, J. Jones, J. Johnson, E. Landry, B., Lane, L., Lynch, G., Chela-Flores, J., Jeng, T-W. and 
Bradley, A. (1997) Searching for ice and ocean biogenic activity on Europa and Earth, Instruments, Methods 
and Missions for Investigation of Extraterrestrial Microorganisms, (R.B. Hoover, ed.), SPIE, Vol. 3111 , 
pp. 490-500; 

McCollom, T. M. (1999), Methanogenesis as a potential source of chemical energy for primary biomass production 
by autotrophic organisms in hydrothermal systems on Europa, Jour. Geochem. Res. Vol. 104 , No. E12, 
pp. 30,729-30,742. 

McCord, T.B., Hansen, G.B., Clark, R.N., Martin, RD., Hibbitts, C.A., Fanale, F.P., Granahan, J.C., Segura, NM., 
Matson, D.L., Johnson, T.V., Carlson, R.W., Smythe, W.D., Danielson, G.E., and the NIMS Team (1998) 
Non-water-ice constituents in the surface material of the icy Galilean satellites from the Galileo near-infrared 
mapping spectrometer investigation. Jour. Geophys. Res. Vol. 103 , No. E4, pp. 8603-8626. 

Pappalardo, Robert T. James W. Head and Ronald Greeley ( 1 999) The hidden ocean of Europa, Scientific American, 
pp. 34^3. 

Parker, B.C., Simmons, Jr., G.M., Wharton, Jr., R.A. Seaburg, K.G. and Love, F. Gordon (1982) Removal of 
organic and inorganic matter from Antarctic lakes by aerial escape of bluegreen algal mats, J. Phycol. Vol. 18 , 
pp. 72-78. 

Prieur, D. (2002) Life detection on Europa: Metabolic signatures, Europa Focus Group Workshop 3, Arizona, 
USA, p. 41. 

Pethrick, R.A. (1982) Molecular Interactions Vol. 3, In: H. Ratajczak and W.J. Orville (eds.) Thomas, John Wiley 
and Sons, New York. 

The Situation in Europa ’s Ocean 


^ Box 351310, University of Washington, Seattle, WA 98195, USA, ^Arizona 
State University Department of Chemistry, AZ, USA and ^Westfdlische 
Wilhelms ^ Universitdt, Institut fiir Planetologie, Munster, Germany 

1. Introduction 

Jupiter’s three innermost moons experience tidal forcing due to the 4:2:1 orbital resonance 
they share. In lo, the closest, the energy dissipated hy flexure of the moon’s mantle is enough 
to make it the most volcanically active body in the solar system. In Europa, dissipation may 
be vary from a tenth to only a hundredth that in lo, but in theory this is still sufficient to 
melt much of the 170 km of ice (Anderson et al 1997) covering its surface and provide a 
moderate heat source (Hussman 2003). In fact, surface geology and planetological proper- 
ties measured by the Galileo probe support the idea that Europa has an ocean perhaps as 
deep as 160 km, with a primary salt composition of Mg and Na sulfates (Greenberg et al 
2000). With the aim of including pressure effects in future simulations of composition and 
dynamics in the ocean, we And predictions of supcrt92 software consistent with experi- 
mentally obtained molar volumes around 50°C and up to 2000 atm, roughly the pressure 
at the base of Europa’s ocean. Understanding hydrothermal activity in Europa’s crust, in 
the past and possibly in the present, is crucial to understanding dynamics and chemistry 
of the ocean as a whole, and for evaluting any biological activity that may have occured 
during the moon’s history. In this paper we explore the limits of theoretical exploration of 
Europa’s ocean, highlighting areas for further research. 

2. Evidence for a Europan Ocean 

Voyager in the 1970s and Galileo in the 1990s both scanned the surface of Europa, revealing 
an icy moon marked by a scarcity of craters and an array of cracking features. These 
suggest a young surface — less than 50 million years old — altered by continuous tidal flexing 
(Greenberg et al 2000). Gravity data from Galileo set the H 2 O thickness in the range of 
100-200 km (Anderson et al 1997). The possibility that this is consistent with a convecting 
ice subsurface is eliminated, at least in part, by the magnetic held signature. Induced by 
Jupiter’s held, Europa’s field appears to origininate near its surface, within the H 2 O covering, 
for which the most likely explanation is some amount of ion-containing liquid (Kievelson 


J. Seckbach et al. (eds.), Life in the Universe, 261 - 264 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


1999). The ice covering’s thickness is further limited by arcuate cracking features, which 
can be explained by a changing direction of crustal stress only if the ice is no more than a few 
kilometers thick (Hoppa 2001). The ice is probably at least a few km thick however, since 
moderately sized craters exhibit a central upwelling feature, excavated from solid material 
under the impact site (Turtle and Pierazzo 2001). Along surface cracks, and also in so-called 
chaos regions where melt-through events appear to have occured, a non-icy component is 
visible. This is thought to have resulted from deposition of dissolved constituents during 
sublimation of liquid. Surface near-infrared spectra for the non-icy component are consistent 
with sodium and magnesium sulfate, and carbonate salts, an indicator of ocean composition 
(McCord et al 2000). 

3. Compositional Modeling 

Some researchers have tried to constrain the composition of Europa’s ocean based on 
surface data (Kargel et al 2000, Spaun and Head 2001, Zolotov and Shock 2001). Assuming 
the moon formed from representative chondrite meteorites — those representative of bulk 
composition of Jupiter’s region in the early solar nebula — the authors take all volatile content 
as the proto-ocean and allow this to proceed to chemical equilibrium, precipitating brine 
salt as it does so. These qualitative models can hint at pH, nutrient flux, and geochemistry in 
Europa’s ocean, but are not accurate enough to factor into dynamical calculations. A large 
problem, one that affects many domains of chemical research, is the lack of pressure data 
for aqueous solutions. Chemical models fit volumentric and other behavior to known values 
measured in the laboratory. Where these are not available the authors must extrapolate. 
Because pressure effects are secondary in significance to temperature effects, and also 
more difficult to obtain, they have been neglected as subjects for research. The physics 
of pressurized solutions may be crucial to the chemistry of Europa’s ocean, however, as 
pressures in the base of Europa’s ocean are much higher than those at average depth in 
Earth’s ocean (2000 vs 500 atm). The situation is changing as new techniques for finding 
equations of state are developed (Abramson et al 1999). As will be shown in a future paper, 
we And supcrt92 (Shock et al 1992) accurate to 5% up to 2000 atm for Na 2 S 04 at 325-375 K. 
Eor much of Europa’s ocean a model suited to lower temperatures is more appropriate. Eor 
this reason, Kargel et al (2000) and Spaun and Head (2001) used the EREZCHEM package 
(Mironenko 1997). Though EREZCHEM contains no parameterization for pressure, its 
extrapolated databases have proven accurate for applications at atmospheric pressure ( 1 atm) 
(Marion 1999). The author of EREZCHEM is currently working on a pressure-corrected 
version (personal communication). Supcrt may still be appropriate for modelling chemistry 
of Europa’s ocean if one considers the possibility of hydrothermal activity in the crust. 

4. Hydrothermal Systems 

If the ice covering Europa’s ocean is very thin, tidal dissipation will occur almost exclusively 
in the mantle. One can envisage a situation in which the initially higher dissipation from 
greater orbital eccentricity leads to a thin ice shell. The situation could then be maintained 
if the cmst is sufficiently plastic and if enough tidal dissipation occurs throughout Europa’s 


history. In any case, seafloor spreading is not expected to occur on Europa. Indeed, the ab- 
sence of an intrinsic magnetic field suggests core convection is not occuring there, so mantle 
convection is not driven by the same mechanism as it is in Earth’s mantle. In the absence of 
as active a mantle, seafloor volcanism may still occur on Europa — and probably did occur 
in its early history — due to the exothermic conversion of peridotite rock to serpentine. On 
Earth, the Lost City hydrothermal system is estimated to be 34,000 years, old based on 
radiocarbon dating (Eruh-Green et al 2003). Estimates of heat provided by serpentinization 
are consistent with this age, making for the feasible existence of hydrothermal systems 
supported by this mechanism alone. The depth of flow through porous rock under the sys- 
tem remains to be determined, leaving undetermined parameters in the understanding of 
chemically driven hydrothermal systems. In the crust of Europa ’s ocean it may be that water 
is able to penetrate more deeply owing to the lesser gradient in pressure, so that a greater 
reservoir for chemical heat generation is available. If porous flow is localized to the azimuth 
of the Europan body facing Jupiter, slow rotation of the mantle body may have sustained 
localized Lost City analogues for a significant portion of the moon’s history, possibly to 
the present. The specifics of serpentinization in Europa ’s crust will be discussed in a future 

5. Prospects for Life 

Some estimates of “biopotential” have been made for Mars and Europa, planets of interest 
to astrobiologists (Jakosky and Shock 1998, Chyba 2000, Zolotov and Shock 2003). These 
have always looked at total energy input to estimate the overall planetary productivity that 
could be supported, with the apparent intention of emphasizing that planetary explorers 
should not expect to find abundant or complex life under the Europan ice shell. Gaidos 
et al (2002), Jakosky et al (1998), and Shock et al (2003) note that only the less efficient 
metabolic pathways of methanogenesis and sulfur reduction are available in the absence 
of oxygen. Chyba (2000) points to the interaction of Jupiter’s strong radiation field with 
impurities in Europa’s ice as an additional source of energy for biota, but he still seems 
to agree with other authors that only microbial life can exist in the ocean. However, the 
global input of energy is less important if much of that energy is localized to support a 
hydrothermal community, and if the center of hydrothermal activity moves slowly enough 
for the hosted community to migrate with it. As described in the previous section, chemical 
heat is a more likely source for Europan hydrothermal energy, but even this may be sparse 
if fresh peridotite is not periodically exposed to Mg-containing water. Doubtless, Europan 
hydrothermal systems resemble colder systems on Earth — like those under Antarctic ice — 
more than the extensive, hot systems at mid-ocean ridges. Unfortunately, little is known 
about such systems, since their exploration even on Earth has begun only in the last decade 
(Dahlmann et al 2001). 

6. Summary 

We review evidence for an ocean on Europa, pointing out where chemical and physical data 
are lacking for simulation and comparison with Earth-systems. Comparing experimental 


volumes for Na 2 S 04 with those predicted by supcrt92, we find supcrt92 agrees within 10% 
around 50°C, up to a pressure of 2000 atm. This is sufficient for future modeling of dynamics 
and composition of Europa’s ocean, and to begin examining the role of serpentinization in 
ocean processes. 

7. References 

Abramson, E.H., Brown, J.M. and Slutsky, L.J. (1999) Applications of Impulsive Stimulated Scattering in the 
Earth and Planetary Sciences. Annu. Rev. Phys. Chem. 50, 279-313. 

Anderson, J.D., Lau, E.L., Sjogren, W.L., Schubert, G. and Moore, W.B. (1997) Europa’s Differentiated Internal 
Structure: Inferences from Two Galileo Encounters. Science, 276, 1236-1239. 

Chyba, C.F. (2000) Energy for Microbial Life on Europa. Nature, 403 , 381-382. 

Dahlmann, A., Wallmann, K., Sahling, H., Sarthou, G., Bohrmann, G., Petersen, S., Chin, C.S. and Klinkhammer, 
G.P. (2001) Hot Vents in an Ice-cold Ocean: Indications for Phase Separation At the Southernmost Area of 
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Friih-Green, G. L., Kelley, D.S., Bemasconi, S. M., Karson, J.A., Ludwig, K.A., Butterfield, D.A., Boschi, C. and 
Proskurowski, G. (2003) 30,000 Years of Hydrothermal Activity at the Lost City Vent Field. Science, 301 , 

Gaidos, E.J., Nealson, K.H., and Kirschvink, J.L. (1999) Life in Ice-Covered Oceans. Science, 284, 1631—1633. 

Hussman, H. (2003) Europa’s Ocean and the Orbital Evolution of the Galilean Satellites. Dissertation Thesis, 
Institut fiir Planetologie, University of Munster. 

Jakocsky, B.M., and Shock, E.L. (1998) The Biological Potential of Mars, the Early Earth, and Europa. J. Geophys. 
Res., 103 , 19359-19364. 

Kargel, J.S., Kaye, J.Z., Head, J.W., Marion, G.M., Sassen, R., Crowley, J.K., Ballesteros, O.P., Grant, S.A., and 
Hogenboom, D. (2000) Europa’s Crust and Ocean: Origin, Composition, and the Prospects for Life. Icarus 
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Lowell, P. and Rona, P.A. (2002) Seafloor Hydrothermal Systems Driven by the Serpentinization of Peridotite. 
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Marion, G.M., Farren, R.E., and Komrowski, A. J. (1999) Alternative Pathways to Seawater Freezing. Cold Regions 
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Mironenko, M.V., Grant, S. A., G.M. Marion, and Farren, R.E. (1997) FREZCHEM2: A Chemical Thermodynamic 
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McCord, T.B., Hansen, G.B., Fanale, F.P., Carlson, R.W., Matson, D.L., Johnson, T.V., Smythe W.D., Crowley, 
J.K., Martin, P.D., Ocampo, A., Hibbits, C.A., Granahan, J.C., and the NIMS Team (1998). Salts on Europa’s 
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Spaun, N.A. and Head, J.W. Ill (2001) A Model of Europa’s Crustal Structure: Recent Galileo Results and 
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Techniques for identifying molecular structures 


The International Center for Genetic Engineering and Biotechnology 
New Delhi, India 

There is no fundamental difference between a living organism and lifeless matter. The complex 
combination of manifestations and properties so characteristic of life must have arisen in the 
process of the evolution of matter. 

A.I. Oparin 

In order to identify life outside of a terrestrial paradigm we examine the Jovian moon, 
Europa as a potential source for biological material. The selection of biological targets is 
based on an investigation of convergent evolution as a universal precept in eukaryote devel- 
opment (Chela-Flores, 1998). Analytical techniques have benefited from multi-disciplinary 
efforts that have led to the creation of the first functional microscopic-scale laboratories 
that can perform a concerted series of “hyphenated” functions. Devices contained within a 
specialised Europan lander (Naganuma and Uematsu, 1998) will have the ability to gather 
samples, screen for promising biosignatures, and present sufficient data to accurately deter- 
mine the characteristics of the samples. Application of these “labs-on-a-chip” (Wang et al, 
2001) holds great promise in the search for life out of our own biosphere. The question 
of whether life exists elsewhere in the universe needs to be pertinent to the novel search 
paradigms afforded by missions to other potential planets. Data inferring presence of liquid 
water under ice cover on the Jovian moon Europa has made it a candidate for being a possi- 
ble source of extra-terrestrial life (Reynolds et al., 1987). In the event of a rare opportunity 
for the direct sampling of the Europan surface and sub-surface (Chyba and Philips, 2002), 
we should examine whether life could be present in some form that has not evolved on 
Earth. Target and search criteria should be addressed as to whether evolution is a universal 
prerogative, or simply a terrestrial artifact. A search based on assays suitable for determin- 
ing whether convergent evolution is a universally valid paradigm should also be open to 
the possibility of identifying higher organisms (Chela-Flores, 1998). Evolutionary classifi- 
cation of life gained a solid basis when Carl Woese propounded a novel method (Woese, 
1987), using contemporary technology, that identifies those characteristics of organisms that 
could indicate evolutionary progress. It is necessary to identify aspects that are conserved 
enough in order to identify, yet are variable enough to allow an evolutionary development 
to be observed. This would imply an “earth-centric” approach (Conrad and Nealson, 2001) 
to the search for life in the universe and presupposes evolutionary criteria to be universally 
valid. The model of convergent evolution raises pertinent questions (Doolittle, 1994: Sette 
et al., 2003), as different organisms often develop similar traits, that can be explained in 


J. Seckbach et al. (eds.), Life in the Universe, 265 - 267 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


a variety of manners (Dauplais et al, 1997). In order to evidence the level of similarity, a 
common method is to create a battery of analytical probes that are known to conjugate with 
a previously identified analyte, and that can signal the level of interaction in a quantifiable 
manner. Interactions that have been evaluated in the known biosphere can be extrapolated 
to an unknown, but believed to be isolated, biosphere (Caetano-Anolles, 2003). In the case 
of a non earth-centric search for life, the method for evaluation must be de-coupled from 
what is considered to be life in our biosphere or in any habitability zone (Sagan, 1964). 
Life as an unknown target can still be identified and quantified according to consideration 
of its inextricable properties (Cleland and Chyba, 2002). An inherently earth-centric point 
of view of any earth-bound observer can be deconstructed in order to identify basic char- 
acteristics necessary for alternative forms of life to exist. Basic elements that can present 
emergent properties, such as topology and chirality (Bonner, 1995) could be identified and 
interpreted, though it may be some time before we obtain the knowledge necessary to prove 
the biogenicity of a purported biogenic signature, or at least that it has not been formed 
abiotically. Observable energy disequilibria may be an indication of the existence of life, 
suggesting a form of energy transduction such as in metabolism/catabolism (Bhattacherjee 
and Chela-Flores, 2003), or for replication at either molecular or cellular levels. In order 
to obtain sufficient data, micro-scale (chip based) devices permit most automated multistep 
assays (Anderson et al., 2000) derived from bench-top systems with advantages of speed, 
cost, portability, and reduced energy/solvent consumption. Studies of mechanosynthesis of 
molecular machine systems will enable the development and production of a wide range of 
micro-components (Drexler, 1994). Attention must be paid to any influence that the analyt- 
ical techniques may have on the sample under analysis (Fukushi et al, 2003), as positive 
results in the search for life in the universe will surely have far-reaching effects on life and 
society in our own biosphere. 


Anderson RC, Su X, Bogdan GJ and Fenton J (2000). A miniature integrated device for automated multistep 
genetic assays. Nuc. Acids Res. 28(12):e60. 

Bhattacherjee AB and Chela-Flores J (2004). Search for bacterial waste as a possible signature of life on Europa, 
in this volume. 

Bonner WA (1995). Chirality and life. Orig Life Evol Biosph. 25(1-3): 175-90. 

Caetano-Anolles G and Caetano-Anolles D (2003). An evolutionarily structured universe of protein architecture. 
Genome Res. 13(7): 1563-71. 

Chela-Flores J (1998). A search for extraterrestrial eukaryotes: physical and paleontological aspects. Orig Life 
Evol Biosph. 28(4-6):583-96. 

Chyba CF and Phillips CB (2002). Europa as an abode of life. Orig Life Evol Biosph. 32(l):47-68. 

Cleland CE and Chyba CF (2002). Defining ‘life’. Orig Life Evol Biosph. 32(4):387-93. 

Conrad PG and Nealson KH (2001). A Non-Earthcentric Approach to Life Detection. Astrobio. l(l):15-24. 

Dauplais M et al., (1997). On the Convergent Evolution of Animal Toxins. JBC. 272(7):4302^309. 

Doolittle RF (1994). Convergent evolution: the need to be explicit. Trends Biochem Sci. 19(l):15-8. 

Drexler KE (1994). Molecular nanomachines. Annu Rev Biophys Biomol Struct. 23:377^05. 

Fukushi D et al. (2003). Scanning Near-field Optical/Atomic Force Microscopy detection of fluorescence in situ 
hybridization signals beyond the optical limit. Exp Cell Res. 289(2):237^4. 

Naganuma T and Uematsu H (1998). Dive Europa: a search-for-life initiative. Biol. Sci. Space. 12(2):126-30. 

Oparin Al (1968). Life, its nature, origin, and evolution. Moscow: Nauka. 173pp. 

Reynolds RT, McKay CP and Kasting JF (1987). Europa, tidally heated oceans, and habitable zones around giant 
planets. Adv Space Res. 7(5):125-32. 


Sagan C (1964). Exobiology: a critical review. Life Sci Space Res. 2:35-53. 

Sette A et al. (2003). Class I molecules with similar peptide-binding specificities are the result of both common 
ancestry and convergent evolution. Immunogenetics. 54(12):830-41. 

Wang J, Ibanez A, Chatrathi MP, Escarpa A (2001). Electrochemical enzyme immunoassays on microchip plat- 
forms. Anal Chem. 73(21):5323— 7. 

Woese CR (1987). Bacterial evolution. Microbiol Rev. 51(2):221-71. 



^The International Centre for Genetic Engineering and Biotechnology, 
New Delhi, India, and ^The Abdus ICTP Strada Costiera 11; 34136 
Trieste, Italy, and IDEA, Caracas, Venezuela 

Abstract. The opportunity for direct examination of the Europan surface and sub-surface calls 
for a systematic and deductive approach to experimental design. To avoid the limitations of our 
inherent Earth-centric definition of life (Nealson et al. , 2002), we would be forced to examine 
a wide range of potential bio-signatures to guide more specific biological experiments (Chela- 
Flores, 2003). It is also important to look for recurring features that are important from the 
evolutionary history of our own biosphere (Zakon, 2003). Of the many candidate molecules, 
the structurally heterologous superfamily of voltage-gated cation channels is an evolutionary 
sensitive group of molecular structures, the single varieties of which can be easily distinguished. 
Implementation of the analytical aspects of this experiment would require remote control of 
miniaturized robotic systems. These mechanisms are under constant evolution since their uses 
are strongly tied to commercial, scientific and military interests. One paradigm for feasibility 
studies could come from data inferring the reprocessing of ice covering a Europan ocean. 
Reprocessing could be inducing life forms extant in the liquid water subsurface towards the 
ice covering, as it has already been demonstrated at the frozen surfaces of Antarctic lakes 
(Bhattacherjee and Chela-Flores, 2004), and as it has been suggested by geophysical analysis 
of the Galileo images of the icy surface of Europa (Greenberg et al, 2002). The proposed 
series of experiments can be carried out in situ either within a submersible in the ocean beneath 
the ice layer (carried and launched from a cryobot), or even on the surface ice itself. Results 
from a preliminary examination of the environment would be used to determine the conditions 
necessary for sampling and pre-processing of any material of possible biological origin. Many 
techniques are currently available for identifying targets according to their molecular structure 
and their chemical-physical characteristics: 

- novel sampling and isolation methods, 

- specific antibodies or diabodies engineered as molecular probes, 

- micro-arrays based on site-specific immobilization of complementary molecules, 

- microscopy and micro-sensors for visualization/digital sampling of positive results. 

New challenges will arise from the novel settings and will have to be addressed, singly, well 
in advance of any preliminary exercises. Moreover, a myriad of practical applications could be 
developed by addressing pertinent, emerging questions relating to: 

- stability of sensitive organic material over a large period of time, and extreme condi- 


J. Seckbach et al. (eds.), Life in the Universe, 269 - 273 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


maintenance of biological activity within silica-, or hydro-micropatterned biogels, 
multiplexing in a microfluidic (lab-on-a-chip) environment, 

miniaturization of analytical devices such as microscopes and their power sources. 

1. Introduction 

Identification of biomolecules is a common process that is approached in a concise and 
systematic manner. When applied to the search for life in the universe many potential 
targets and recognition techniques can be envisioned. These can be refined by seeking with 
evolutionary criteria in an environment where water is available (DesMarais et al, 2002). 
The problem of rational target selection is to single out known bio-signatures and evaluate 
their placement on an evolutionary timescale. Selection of a target based on the central 
dogma of molecular biology (Crick, 1958), which states that the flow of genetic information 
is from DNA, through RNA, to protein, is open to the idea that any of these key molecules 
could be, or could have once been (Woese, 2001), sources of hereditary data in some place in 
the universe (Crick, 1966 and 1970). The examination of samples of unknown composition 
yields results that are tied not only to the nature of the material under scrutiny but also to the 
conditions under which they are examined (Vreeland et al, 2002). The delicate pleiotropic 
nature of protein-protein interactions, for instance, can be permanently affected by minimal 
variations that would alter important conformational interactions. There are methods for 
the successful recovery of biological material from problematical sources (Vreeland and 
Rosenzweig, 2002) since insufficient levels of sterility, contamination from other sources, 
or less than optimal reaction conditions always lead to unreliable results (Nicastro et al, 

2. Molecular Techniques 

Structural information for the identification of life could be sought in membrane compo- 
sition (channels, peptidoglycans, lipids, chirality) or in the form of genetic information 
(DNA, RNA . . . ). The lack of available information about non-terrestrial macromolecules, 
however, makes it difficult to seek life through molecular probing of these components, 
though all can be analysed with specific assays: sugars (DeAngelis, 2002), proteins (Zakon, 
2002) and regulatory machinery of gene expression (Conant and Wagner, 2003). Molec- 
ular subtyping methods can seek differences in control of fatty acid (Tornabene et al, 
1980), protein or nucleic acid (Woese and Fox, 1977) biosynthesis. Many evolutionarily 
conserved biomolecules could serve the purpose of attempting to ground a universal tree of 
life. Families of proteins where there are conserved structural elements, or domain-specific 
features (Marck and Grosjean, 2002), are thought to lead to ancient origins or even to a 
last universal common ancestor (LUCA) (Ouzounis and Kyrpides, 1996). The link between 
structure and function is apparent in the conservation throughout evolution of families of 
proteins that perform essential tasks (Ruta et al., 2003). Ion channels belong to a large 
family of related genes that regulate vital functions. The simplest channels are found in all 
kingdoms of life. Ion channels consist of assemblies of subunit components (Hille, 2001) 


and thus share aspects of their memhrane topologies (Miller, 2000). However, diverse ion 
specificities (Jeziorski et al, 2000) and methods of functional regulation (Doyle et al, 
1998) make ion channels ideal targets for probes seeking differentiation by evolutionary 
criteria (Harte and Ouzounis, 2002) with, for example, semisynthetic libraries (Braunagal, 
2003) that lend themselves to rational design and chemical synthesis. In order to assure 
the correct interpretation of image data obtained in loco, it is important to sample data at 
a sufficiently high resolution so that any further enhancement does not alter the acquired 
data. Light microscopy can utilize illumination sources that can be easily varied, such as 
with filtered short wavelength radiation that can cause fluorescent substances to produce 
emission spectra (Kain et al., 1995). Green fluorescent protein (GPF) has been used as a 
specific reporter gene for ion channel expression (Marshall et al, 1995). Confocal (laser 
scanning) microscopy (CLSM) offers a further advantage of being able to increase spatial 
resolution. Multi-photon microscopy uses short pulses of low energy, infra-red, light to 
excite a restricted cross-section within the sample without the need for confocal apertures. 
This increases the photostability of fluorescent molecules (Geddes et al., 2003), though a 
recently developed alternative to organic molecules for immunocytochemical imaging is 
quantum dot technology. The higher quantum yield and stability of quantum dots could 
solve the major problem associated with a large amount of parallel assays and with the 
long latency period between assay set-up and performance (Tokumasu and Dvorak, 2003). 
They can be combined into highly specific bioconjugates for studying genes or proteins in 
applications that are not envisioned with traditional organic dyes and fluorescent proteins 
(Medintz et al., 2003). Nuclear magnetic resonance (NMR) can be used to detect 3 dimen- 
sional (3D) placements of unmarked individual atoms (Doughtery et al., 2000), even in 
extremely low magnetic fields (McDermott et al., 2002). Analytical systems such as scan- 
ning probe microscopes already enable direct visualization and manipulation of individual 
macromolecules (Malayan and Balachandran, 2001); a key interest in process miniaturisa- 
tion (PIM) in the field of molecular diagnostics (Brush, 1999). A new generation of scientific 
instruments is in development that can be adapted to the context of planetary exploration. 
Novel power sources (Fennimore et al., 2003) and remote robotic control would guaran- 
tee the completion of a mission even in unforeseen circumstances. Microfabricated devices 
have already been adapted for transcript expression profiles of genes related to ion channels, 
with the ability to identify changes down to channel subunit level (LeBouter et al., 2003). 
Biochips are used that permit electrophoretic separations and highly specialized applica- 
tions of molecular biology. Though several different matrices and protocols are available 
for microarrays, storage periods remain very limited (Angenendt et al, 2002). Biomimetic 
systems apply novel production methods and materials for creating surface moieties similar 
to those using proteins or nucleic acids that are made by bio-systems. The transport of 
fluids through nanoscopic conduits (Drexler, 1994) will allow single molecules of DNA to 
be analysed. It has been a long established goal to guide complex sequences of actions in 
simple nanoscale systems in order to create more intricate patterns (Deamer and Branton, 
2002). Alternative biogels are being derived from a marine sponge, Tethya aurantia, that 
produces a protein group call silicateins responsible for biosilicate formation under benign 
conditions (Cha et al., 1999). Molecular-scale channels are essentially entirely interfaced 
with no bulk fluid; thus, a complete understanding and control of interfacial chemistry on 
the nanometer scale to obtain a stable microfluidic network cannot be underestimated (Kim 
et al, 2001). The challenge of finding life in the universe is driving research to develop 


more efficient scientific instruments that will not fail to benefit applications in every field, 
and in every biosphere that may be found to exist. 

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Current Status and Expected Exobiological Return of the 
Cassini-Huygens Mission 


^LISA, CNRS and Universites Paris 12 et Paris 7, Avenue du General de 
Gaulle, 94010 Creteil, Cedex France, ^ESA Research and Scientific 
Support Department, ESTEC/SCl-SB, 2200 AG Noordwijk, The 
Netherlands, and ^ Institute for Astronomy, University of Hawaii, 2680 
Woodlawn Drive, Honolulu, HI 96822 USA 

1. Introduction 

Many space missions of exo/astrobiological importance have been launched since the be- 
ginning of planetary exploration with space probes more than 40 years ago. The most 
exobiologic ally oriented one was certainly the Viking mission to Mars, which became the 
first extraterrestrial planetary target to be searched for evidence of (extinct and extant) life. 
However, there is another category of extraterrestrial planetary bodies of prime interest 
for Exobiology: bodies where a complex organic chemistry is taking place. Titan, Saturn’s 
largest satellite, with its thick nitrogen atmosphere, rich in organics in the gas and aerosol 
phases, and with many analogies to the early Earth, is probably, with the comets, one of the 
most exobiologically interesting bodies of this second kind. 

The Cassini-Huygens mission to the Saturn system is particularly devoted to study 
in great detail Titan’s exotic world, where we may find many data of paramount interest 
for our understanding of prebiotic chemical and physical processes. Cassini-Huygens, the 
most ambitious mission ever sent to the outer solar system, is designed to explore in detail 
the Saturnian system. A joint collaboration between NASA and ESA, it involves a wide 
cooperation among 18 countries from both the United States of America and Europe. 

This paper presents the current status of the Cassini-Huygens mission. It briefly describes 
what we already know about Titan, especially about the organic chemistry which is going 
on in the different parts of the satellite and what we do not know, especially the many 
questions of exobiological importance which are still unresolved. It finally presents which 
of these questions Cassini-Huygens is designed to address, and it discusses more generally 
the exobiological implications of the potential scientific return of this very exciting planetary 


J. Seckbach et al. (eds.), Life in the Universe, 275 - 280 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. The Cassini-Huygens Mission 

The NASA-ESA Cassini-Huygens spacecraft was successfully launched at 4:43 a.m. EDT 
by a Titan IVB/Centaur rocket on October 15, 1997, from Cape Canaveral, Elorida. The 
spacecraft, which consists of a Saturn orbiter (Cassini) and a Titan atmospheric probe 
(Huygens) is on a seven-year interplanetary trajectory toward Saturn, that relied on four 
gravity-assist manoeuvres at Venus (in 1998 and 1999), Earth (August 1999) and Jupiter 
(December 2000) to reach its final destination. It is targeted to reach Saturn in late June 2004, 
with a Saturn orbit insertion on 1st July 2004. Then, Cassini will embark on a 4-year tour of 
the Saturnian system. At the end of 2004, after two initial Titan encounters, it will release 
the Huygens probe on the third orbit around Saturn on 25th December 2004. Huygens 
will penetrate Titan’s atmosphere and parachute down to the surface on January 14, 2005 
(Matson et al., 2002, Lebreton and Matson, 2002, Kazeminejad et al., 2002; Russell, 2002; 
see also and 

The Cassini/Huygens mission is designed to explore the Saturnian system in great detail, 
including the giant planet, its atmosphere, magnetosphere and rings, and many of its moons, 
especially Titan. Titan’s exploration is indeed one of the main objectives of the mission 
which includes multiple opportunities for close remote sensing and in-situ observations of 
Titan with the Cassini orbiter which is planned to complete 74 orbits around Saturn, that 
include 44 close Titan’s fly-by’s, during the four years of the nominal mission (mid-2004 
to mid-2008). Huygens descent will last about 2.5 hours, but if it survives landing, it may 
still function for up to two/three hours on the surface. Many of the twelve instruments of 
the Cassini orbiter and all six instruments of the Huygens probe will study in-situ the many 
chemical and physical aspects of the atmosphere and the surface of Titan. They will provide 
much information of crucial importance for extending our knowledge of the complexity of 
Titan’s organic chemistry. 

3. What Do We Already Know About Titan? 

Thanks to the Titan flybys by two Voyagers in the early 80’s and many later observations 
from the ground or Earth orbiting telescopes, we already have an important amount of 
information on Titan. With a diameter of more than 5500 km. Titan, is by the size, the 
second largest moon of the solar system after Jupiter’s Ganymede. It is the only satellite to 
have a dense atmosphere, composed mainly of dinitrogen and methane, with a small fraction 
of dihydrogen, and possibly argon, which has yet to be detected. This atmosphere is nearly 
five times denser than the Earth’s atmosphere, with a surface temperature of 90-100 K and 
a surface pressure of 1.5 bar. As in the Earth’s atmosphere, with water vapor and carbon 
dioxide on the one hand and clouds on the other hand. Titan’s atmosphere also contains 
greenhouse gases, (condensable CH 4 , equivalent to terrestrial H 2 O; non-condensable H 2 , 
equivalent to terrestrial CO 2 ), and anti-greenhouse compounds (aerosols). The thermal 
profile of the lower atmosphere of Titan is very similar to the terrestrial one — although the 
temperatures are much lower there — with a troposphere (90-70 K), a tropopause (70 K) 
and a stratosphere (70-175 K). Moreover, the models of the surface of Titan suggest that 
it is covered — at least partially — with lakes or seas of methane and ethane. Water ice 
has very recently been detected at the surface (Griffith et al., 2003), which opens many 


important exobiological perspectives, including the possibility of presence of liquid water 
on Titan’s surface episodically due to large impacts and the subsequent occurrence of 
prebiotic chemistry in these liquid bodies. 

Titan’s environment is very rich in organic compounds, present in the three components 
of what one can call, again by analogy with our planet, the “geofluid” of Titan; air (gas 
atmosphere), aerosols (solid atmosphere) and surface (solid and liquid bodies). Indeed 
several hydrocarbons and nitriles have already been detected in the gas and condensed 
phases in Titan’s atmosphere. These organics are the products of the photochemistry of 
methane coupled with that of dinitrogen. All the organic compounds which were detected 
in the atmosphere of Titan were also produced in laboratory simulation experiments (Coll 
et al., 1999), together with complex macromolecular products made of C, H and N atoms 
(called “tholins”) and supposed to be the main constituents of Titan’s aerosols (Coll et 
al., 1999; McKay et al., 2001, Ramirez et al., 2002; and refs, included). Many others 
organics, which have not yet been detected in Titan, are also formed during these laboratory 
experiments, which strongly suggests that they are also present in the atmosphere of Titan. 
This is strongly supported by the very recent detection of benzene in Titan’s atmosphere 
through ISO observations (Coustenis et al., 2003; and refs included), the presence of which 
was expected from the results of laboratory simulation experiments. In the same way, the 
detection of water, in gas phase, in the atmosphere (Coustenis et al., 1998) although at 
very low concentration, together with the presence of CO and CO 2 , allows us to consider 
the presence of oxygenated organic compounds. Recent laboratory experiments performed 
on model atmospheres of Titan including traces of CO, show that the main O-containing 
organic product is oxirane (Coll et al., 2003). 

4. What We Do Not Know About Titan? 

Many questions of exo/astrobiological importance concerning Titan remain unsolved 

1) What is the Origin of the atmosphere and in particular of methane? Indeed the 
existence of methane in Titan’s atmosphere is a major puzzle at present. This gas 
is destroyed so rapidly by photochemistry that the amount we see today will be 
gone in just a few million years. Methane must be continuously re-supplied to the 
atmosphere. The needed source could be a surface reservoir of methane through 
the lakes and seas mentioned above, or an external source (cometary impacts?) or 
a subsurface reservoir involving methane hydrates (Mousis et al., 2002, and refs, 
included) and cryovolcanism, or even biological sources (Fortes, 2000), involving 
methanogen micro-organisms (even if this hypothesis looks very unlikely). 

2) In relation to this first question, are there liquid bodies on Titan’s surface? Earth 
based observations confirm a non-homogeneous surface with dark and clear re- 
gions. The very recent radar data of Titan (Campbell et al., 2003) is fully compatible 
with the presence of several areas of liquid hydrocarbons on Titan’s surface. But the 
information about the surface state and chemical composition is still very limited. 

3) What is the chemical composition of the aerosols? What are their elemental and 
molecular compositions? Are they made of organic tholins, covered by volatile 


material, as suggested by experimental and theoretical modelling (Raulin and 
Owen, 2002 ; and refs, included). 

4) Is there lightning in the troposphere and are there organic processes in the tropo- 
sphere and surface, as suggested by theoretical models? 

5) Is there a subsurface water-ammonia ocean, as indicated by modeling of the in- 
ternal structure of Titan (Grasset and Sotin, 1996; and refs. Included)? Is there 
an organic/prebiotic chemistry going on in this hypothetical ocean? Is there life 
present in this environment? 

6) Is Titan’s organic and almost prebiotic chemistry even more complex than we ex- 
pect? Are 0-bearing atoms involved in the surface organic chemistry, because of 
dissolved CO and precipitated CO 2 , or through a multiphase organic chemistry 
involving water ice recently detected (Griffith et al., 2003), or involving tempo- 
rary liquid water produced through hypothetical cryovolcanism or meteoritic or 
cometary impacts? 

7) In direct relation to the previous questions, are there macromolecular materials 
abundant in Titan’s environment? If yes what is their structure? Do they include 
oligomers, in particular of HCN and C 2 H 2 ? Are there purine and pyrimidine bases 
present? Are there amino acids or their analogues? Are pseudo-polypeptides in- 
cluded in Titan’s organic oligomers (Raulin and Owen, 2002)? 

8) Is chirality present in Titan organic chemistry? Is there an enantiomeric excess in 
chiral molecules which may be present in the aerosols and/or on the surface or even 
in the subsurface? Is chirality also present in the macromolecular materials? The 
low temperature of Titan’s environment should protect any enantiomeric excess 
against racemization, thus the study of chirality in Titan’s chemistry is of prime 
importance and could yield crucial information on the origin of chirality in living 

5. What Do We Expect from Cassini-Huygens? 

Several of the questions discussed in the above section will be approached in great detail 
thanks to the Cassini-Huygens mission (Wilson, 1997; Matson et al., 2002). 

Several instruments of the orbiter and five of the six instruments of the probe will 
provide data of exobiological interest. The optical remote sensing instruments of the orbiter 
(especially CIRS and UVIS) will determine the chemical composition of different zones 
of Titan’s atmosphere and should be able, in particular, to detect many organics, including 
new species and allow the determination of their vertical concentration profile. The Cassini 
Radar will be able to map Titan’s surface through the haze layers, and to determine the 
presence and distribution of liquid bodies. VIMS will also provide information on and 
mapping of the chemical composition of the surface. 

On the Huygens probe (Russell, 2002), the GC-MS instrument, a gas chromatograph 
with three GC capillary columns, coupled to a quadrupole mass spectrometer, (Niemann 
et al., 2002) will perform a detailed chemical analysis of the atmosphere — including 


molecular and isotopic analysis — during the 2.5 hours of descent of the probe, and perhaps 
of the surface, after landing. The ACP experiment will collect the atmospheric aerosols, 
heat them at different temperatures including at high temperature to pyrolyse the refractory 
organic materials (tholins) and transfer the produced gases to the GC-MS instrument for 
molecular analysis (Israel et al., 2002). This will provide the first direct in situ molecular 
and elemental analysis of Titan’s hazes. HASl will determine, in particular, the pressure 
and temperature vertical profiles. DISR will measure the atmosphere radiation budget, de- 
termine the cloud structure and take images of the surface. DISR should provide evidence 
before impact whether Huygens is approaching a liquid surface. SSP and the rest of the 
payload that will remain operational after impact, will provide information on the physical 
state and chemical composition of the surface. 

6. Conclusions 

Several of the conditions necessary for planetary chemistry to evolve toward complex or- 
ganic and prebiotic systems are present on Titan (Raulin & Owen, 2002, and refs, included): 
a dense and midly reducing atmosphere, a variety of efficient energy sources, a complex 
atmospheric system with aerosols and the possible presence of surface liquid bodies. 

As early as mid-2004, Cassini-Huygens, a great Human adventure with an unmanned 
planetary mission to explore the Saturn System, will provide many new data on Titan, 
essential for the field of exobiology. Its scientific return is expected to be at least one order 
of magnitude greater than that of the Voyager mission. As an example, the CIRS experiment 
has a sensitivity which is 10 to 100 times higher, a spectral resolution 10 times better and 
a spectral range much larger than IRIS, the Voyager IR spectrometer. Since 20 years after 
Titan’s encounter by Voyager, IRIS data are still being analysed, one can easily forecast 
that it will take several decades to fully analyse and interpret all Cassini-Huygens data. 
The prospect of an extended mission after mid-2008 if the Orbiter is still performing well, 
promises to offer many new opportunities for Titan observations, taking advantage of the 
new knowledge acquired with Huygens and the first few years by the Orbiter. 

Laboratory studies are still much needed to make available key data essential for the 
interpretation of the Cassini/Huygens data observations and for theoretically modelling 
Titan’s environment. Much needed laboratory data includes kinetic data related to small 
polyynes and cyanopolynes (Vuitton et al., 2003), and the dielectric properties of the aerosol, 
rain, and surface material (Rodriguez et al., 2003). 

The Cassini-Huygens mission will bring answers to many of the scientific questions con- 
cerning Titan. But several questions will still remain, in particular the problem of chirality 
and most of the questions related to the organic chemistry that is taking place on the surface 
and in the subsurface of Titan. Thus, the scientific planetological and exo/astrobiological 
community is already thinking about post Cassini-Huygens missions, able in particular to 
explore these aspects of the so mysterious world of Titan (Lorenz and Mitton, 2002). 

7. Acknowledgments 

This review work has been supported by grants from the French Space Agency (CNES: 
Centre National d’Etudes Spatiales), University Paris- Val de Marne, and the NASA. 


8. References 

Campbell, D.B., Black, G.J., Carter, L.M. and Ostro SJ. (2003) Radar Evidence for Liquid Surfaces on Titan, 
Science, in press. 

Coll, R, Guillemin, J.-C., Gazeau, M.-C. and Raulin, F. (1999) Report and implications of the first observation of 
C 4 N 2 in laboratory simulations of Titan’s atmosphere. Planet. Space Sci 47 (12), 1433-1440. 

Coll, P., Bernard, J.-M., Navarro-Gonzalez, R. and Raulin, F. (2003) Oxirane: An exotic oxygenated organic 
compound in Titan? Astrophys. J, in press. 

Coustenis, A., Salama, A., Lellouch, E., Encrenaz, Th., Bjoraker, G.L., Samuelson, R.E., De Graauw, Th., 
Feuchtgruber, F and Kessler, M.F (1998) Evidence for water vapor in Titan’s atmosphere from ISO/SWS 
data, Astron. Astrophys. 336, L85-L89. 

Coustenis, A., Salama, A., Schulz, B., Ott, S., Lellouch, E, Encrenaz, Th, Gautier, D. and Feuchtgruber, H. (2003). 
Titan’ s atmosphere from ISO mid-infrared spectroscopy, Icarus, 161, 383^03. 

Fortes, A.D. (2000) Exobiological implications of a possible ammonia-water ocean inside Titan, Icarus 146, 

Grasset, Q. and Sotin, C. (1996) The cooling rate of a liquid shell in Titan’s interior, Icarus 123, 101—123. 

Griffith, C., Owen, T., Geballe, T.R., Ravner, J. and Rannou, P. (2003) Evidence for the Exposure of Water Ice on 
Titan’s Surface, Science, 300 (5619), 628—630. 

Israel, G., Cabane, M., Brun, J.F, Niemann, H., Way, S., Riedler, W, Steller, M., Raulin, F and Coscia, D. (2002) 
The Cassini-Huygens ACP experiment and exobiological implications. Space Science Review, 104 (1^), 

Kazeminejad, B., Lebreton, J.-P, Matson, D. L., Spilker, L. and Raulin, F (2002) The Cassini/Huygens Mission to 
Saturn and Titan and its relevance to Exo/Astrobiology, Proc. 2d European Workshop on Exo-/Astro-Biology, 
E5A-5P518, 261-268. 

Lebreton, J.-P. and Matson, D. L. (2002) The Huygens probe: Science, Payload and Mission Overview, Space 
Science Review, 104(1^), 59-100. 

Lorenz, R. and Mitton, J. (2002) Lifting Titan’s Veil, Cambridge University Press, Cambridge, U.K. 

Matson, D., Spilker, L.J. and Lebreton, J.-P. (2002) The Cassini/Huygens mission to the Saturnian system , Space 
Science Review, 104(1^), 1-58. 

McKay, C.P., Coustenis, A., Samuelson, R.E., Lemmon, M.T., Lorenz, R.D. , Cabane, M., Rannou, P. and Drossard, 
P. (2001) Physical properties of the organic aerosols and clouds on Titan, Planet. Space Sci. 49, 79-99. 

Mousis, O., Gautier, D. and Bockelee-Morvan, D. (2002) An evolutionary turbulent Model of Saturn’s subnebula: 
Implications for the origin of the atmosphere of Titan, Icarus, 156, 162—175. 

Niemann, H.B., Atreya, S.K., Bauer, S.J., Biemann, K., Block, B., Carignan, G.R., Donahue, T.M., Frost, R.L., 
Gautier, D., Haberman, J.A., Harpold, D., Hunten, D.M. D.M., Israel, G., Lunine, J.I., Mauersberger, K., 
Owen, T.C., Raulin, F, Richards, J.E. and Way, S.H. (2002) The Gas Chromatograph Mass Spectrometer for 
the Huygens Probe, Space Science Review, 104 (1^), 551-590. 

Ramirez, S.I., Coll, R, Da Silva, A., Navarro-Gonzalez, R., Lafait, A. and Raulin, F. (2002) Complex Refractive 
Index of Titan’s Aerosol Analogues in the 200-900 nm domain, Icarus, 156(2), 515-530. 

Raulin, F. and Owen, T. (2002) Organic chemistry and exobiology on Titan, Space Science Review, 104 (1^), 

Russell, C.T. (ed.) (2002) The Cassini-Huygens mission. Overview, Objectives and Huygens Instrumentarium, 
Space Science Review, 104 (1^). 

Rodriguez, S., Paillou, R, Dobrijevic, M., Ruffle G., Coll, P, Bernard, J.M., and Encrenaz, P. (2003), Impact of 
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Vuitton, Gee, C., Raulin, F, Benilan, Y., Crepin, C. and Gazeau, M.-C. (2003) Intrinsic lifetime of C4H2*: 
Implications for the photochemistry of C4H2 in Titan’s atmosphere. Planet. Space Sci., in press. 

Wilson A. (Ed.), European Space Agency (1997) Huygens : Science, Payload and mission, ESA SP- 1177. 

Titan ’s Aerosol Analogues 


^Centro de Investigaciones Qmmicas, UAEM Av. Universidad # 1001 
Col. Chamilpa, Cuernavaca, Morelos 62210 Mexico; ^Laboratorio de 
Qmrnica de Plasmas, Instituto de Ciencias Nucleares, UNAM Circuito 
Exterior C. U. Apdo. Postal 70-543, D. F. 04510 Mexico; ^ Laboratoire 
Interuniversitaire des Systemes Atmospheriques, CNRS and Universites 
Paris VII et XU, 61 avenue du General de Gaulle 94010 Creteil 
cedex Prance 

Abstract. The surface of Titan is hidden, in the visible light, by two aerosol layers. The prop- 
erties of these layers have been studied through ground-based and spacecraft observations, by 
theoretical modeling, and by different experimental approaches. Tentative analogues of Titan’s 
aerosols have been synthesized in laboratories to determine their physical, chemical, and op- 
tical properties. It was precisely a careful analysis of the optical properties of the laboratory 
solid aggregates that shows that those properties frequently need a correction factor to ade- 
quately match Titan’s geometric albedo. Trying to hnd an explanation to this fact, there has 
been a continuous search on the physical and chemical properties of the synthesized solids in 
relation to their quality as authentic laboratory analogues. A few reports are available concern- 
ing the chemical composition of laboratory aerosols and such studies varied significantly in 
experimental variables. Hence, there is a need for systematic studies of the solid products syn- 
thesized during simulation experiments devoted to determine their structural features. A brief 
description of the initial steps of such a study focused in the characterization, by analytical in- 
strumental techniques, of laboratory aerosol analogues synthesized from 1-hour laser-induced 
plasma irradiation of a Titan’s canonical atmosphere is presented. Understanding the chemical 
process that originate them and approaching to their chemical characterization can certainly 
help to easily interpret their role in Titan’s atmospheric dynamics. 

I. Introduction 

Laboratory simulation experiments of planetary bodies initiated with one of the most pop- 
ular and well documented: Miller’s replication of Early Earth conditions. This chemically 
oriented experiment was formulated to test the idea that organic compounds that served as 
the basis of Life in our planet formed from a strongly reduced atmosphere (Miller, 1953). 
There has passed 50 years since the report of this classical experiment and during this time 
a great number of modified versions of it has been carried out. It has also inspired the 


J. Seckbach et al. (eds.), Life in the Universe, 281 - 285 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


formulation of innovative laboratory simulations not only to recreate Earth’s scenarios but 
to look into the varied environments found in the planets and moons of our Solar System 
some of which have strongly called Exo/Astrohiology attention. Objects where a prebiotic- 
like chemistry is going on are of the most interesting ones. The satellite Titan with its dense 
atmosphere, rich in molecular nitrogen with a noticeable fraction of methane, appears as 
a planetary- size chemical reactor where a complex organic chemistry occurs in gas and 
condensed phases (Coll et al., 1999; Raulin et al., 1999). 

2. Experimental Conditions 

Laboratory simulations of Titan’s atmosphere environment have demonstrated that long- 
time irradiations of CH 4 and N 2 mixtures with different energetic sources yield sticky, 
dark-color condensed materials proposed as good candidates to mimic Titan’s aerosols 
(Sagan and Thompson, 1984; Khare et al., 1984; Scattergood et al., 1989; Ramirez and 
Navarro-Gonzalez, 2000; Thompson et al., 1991). However, significant differences arise 
because their properties display a strong dependence on the utilized experimental conditions. 
With the purpose of arriving to a more accurate simulation system of Titan’s conditions 
that yields better quality aerosol analogues a protocol has been initiated (Coll et al., 1999; 
Ramirez et al., 2002) and continues under development. A mixture of ultra high purity 
methane and nitrogen gases (1:9), that simulates Titan’s atmosphere, was introduced at a 
pressure of 670 mhar at room temperature, into a round 1.09-liter Pyrex glass flask. The 
mixture was subjected to laser-induced plasma (LIP) irradiation using a Nd-YAG laser with 
a pulse width of 7 ns operating at 10 Hz by 60 minutes. A 1.06 p.m beam was focused at the 
center of the flask using a 5 cm focal distance plano-convex lens with anti-reflection coating. 
The solid collected from the glass flask with HPLC-grade methanol (CH 3 OH) was dried 
and then analyzed by infrared (ETIR) and proton nuclear magnetic resonance (^H NMR) 
spectroscopy. Infrared spectra from a KBr film were recorded in fransmission mode from 
4000 fo 500 cm“' wifh a Nicolel ETIR Magna 560 spectrometer at 2 cm“^ resolution, 
while *H NMR spectrum was obtained from D 2 O-DMSO soluble fractions of the recovered 
aerosol analogue in a 300 MHz Varian instrument. 

3. Results and Discussion 

The strongest absorption bands found in the infrared spectra (Fig. 1) correspond to 
-CH=CH 2 - or aromatic =C-H groups (>3000; 1415 cnT^); -CH 3 (2960-2870; 1440- 
MOO cm-'); -CH 2 - (2925-2850; 1350-1150 cm"'); -C^N (2260-2240 cm-') -C=C- 
(1670-1640 cm”'). The more interesting bands are those that show the presence of the 
double bonds and of the cyano group. It is important to mention that the spectra obtained 
resemble very closely that reported by Coll et al. (1999) where simulations were performed 
using a glow discharge. The fact of finding close similarities between these spectra is re- 
markable because it could mean that we have been able to produce a solid material with 
similar infrared spectroscopic characteristics using different energy sources. This implies 
less dependence on experimental parameters. McDonald et al. (1994) reported the trans- 
mission ETIR spectrum of a polymer obtained from a gas mixing ratio similar to the one 


Figure 1. FTIR (inset) and *H NMR spectra of the recovered solid fraction from Titan’s aerosol analogues 
synthesized after 1-hour LIP irradiation of a 1:9 methane in nitrogen gas mixture. 

used in the present work, but irradiated by a Tesla coil. Even when the general profile of that 
spectrum does not resemble a lot our spectra, they reported the presence of saturated CH 3 - 
and -CH 2 - groups, as well as -C=C-, C=C, -C=N, N-H and tentatively carbonyl groups. 
The primary bands from the 'H NMR analysis demonstrate that the aerosol analogue syn- 
thesized contains saturated and unsaturated aliphatic hydrocarbons due to the presence of 
-CH 3 (0.78 ppm), -CH 2 - ( 1 . 1 1 ; 1 . 1 3 ppm) ; C=C-CH 3 or C=C-CH 3 ( 1 .68 ppm); -CH 2 =C-C 
(2.04 ppm); as well as aromatic hydrocarbons (7.19 and 7.28 ppm), and probably nitriles 
of the type Ph-CN (3.38 ppm) or -C=C-CN (3.45 ppm). 

Limited work has been published so far about the chemical properties, and specifically 
the structural features of analogues for the Titan’s atmospheric aerosols. The information 
collected by these two analytical techniques can help to proposed basic blocks expected to 
be found in the molecular “backbone” of the solids. It is not surprising to hnd the signatures 
of double and triple homo- and hetero-atomic bonds. It is believed that the origin of the solid 
phase begins with a linear polymer having the general structure RiC=NR 2 arising from 
the interaction of gas-phase nitrile groups (McDonald et ai, 1994). It can also come from 
the condensation of residues of unsaturated hydrocarbons and a nitrile group or from two 
triple bond residues. The aromatic fragments detected can be formed from Diels-Alder type 
reactions, which are not difficult to occur since during the irradiation process the vessel con- 
tains a wide variety of reactive species: free radicals, excited molecules, and ionized species 
originated from the original gas mixture constituents as well as from the primarily produced 
molecules. It has been demonstrated that LIP discharges tend to produce mainly alkynes 
and benzene derivatives together with saturated and unsaturated hydrocarbons (Ramirez and 
Navarro-Gonzalez, 2000). In a medium such as the one promoted during the proliferation 
of the plasma, the reactive character of the existent species is displayed and results in the 
recombination of all the primary species. How close the solids experimentally obtained, 
not only from the present work but from other experimental protocols, represent Titan’s 
aerosols (tholins) is still in debate. However parallel to the argumentation proposed in that 


way, it must also exists argumentation aimed to understand the chemical processes that 
originate them and different approaches to elucidate their chemical structure. Studies in this 
manner will certainly help to easily interpret the role of the aerosols in Titan’s atmospheric 
dynamics, and in terrestrial simulation experiments. 

4. Conclusions 

The initial steps of a study dedicated to determine the chemical characterization of Titan’s 
atmospheric aerosol analogues has been initiated. Preliminary results show a lower depen- 
dence on experimental conditions and the presence of chemically interesting fragments of 
molecules. The study will continue with a detailed analysis of the production mechanisms 
that yields the solids from the gas-phase molecules to be able to approach to more accurate 
structural features of the aerosol analogues. Experimental investigations in this sense are 
needed and they are of particularly importance in the perspective of the exploration of Titan 
by the Cassini-Huygens (NASA-ESA) mission, which is expected to provide a tremendous 
amount of new observational data of Titan’s environments, starting in 2004. An efficient 
retrieving of these data requires the availability of many laboratory data, concerning specif- 
ically those of Titan’s aerosol analogues. 

5. Acknowledgements 

This work is being supported by grants from CONACYT (J40449-F) and PROMEP 
(103.5/03/1134). SIR is grateful to ICN-UNAM for permitting the use of their facilities 
for the synthesis of the aerosol analogues and to IQ-UNAM for providing the recorded 
spectra; she is also grateful to the ICTP and co-sponsors of the 2003 Trieste Conference, 
specially to Prof. J. Chela-Flores, for the afforded travel-grant. We appreciate the help 
provided by Prof. J. Seckbach in the formatting process of the manuscript. 

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Raulin, F., Coll, P, Smith, N., Benilan, Y, Bruston, P. and Gazeau, M.C. (1999) New insights into Titan’s Organic 
Chemistry in the Gas and Aerosol Phases. Adv. Space Res., 24 , 453^60. 


Sagan, C. and Thompson, W.R. (1984) Production and Condensation of Organic Gases in the Atmosphere of Titan. 
Icarus, 59, 133-161. 

Scattergood, T.W., McKay, C.P., Borucki, W.J., Giver, L.P., Van Ghyseghem, H., Parris, J.E. and Miller, S.L. 
(1989) Production of Organic Compounds in Plasmas: a Comparison among Electric Sparks, Laser-Induced 
Plasmas, and UV light. Icarus, 81, 413^28. 

Thompson, W.R., Henry, T.J., Schwartz, J.M., Khare, B.N. and Sagan, C. (1991) Plasma Discharge in N 2 + CH 4 
at Low Pressures: Experimental Results and Applications to Titan. Icarus, 90, 57-73. 



^ Laboratoire Interuniversitaire des Systemes Atmospheriques, UMR CNRS 
7583, Universites Paris 12 and Paris 7, CMC, 61 av. du de Gaulle 
F -940 10 Creteil cedex, France. ^ Departamento de Fi'sica, Faculdade de 
Engenharia, Universidade do Porto, 4200-465 Porto, Portugal and 
^Service dAeronomie, Universite de Versailles Saint Quentin, 78035 
Versailles Cedex, France 

I. Introduction 

Titan, the largest satellite of Saturn, has been studied as an exo/astrobiological object for 
several years. Its dense atmosphere is made of nitrogen with a few percent of methane. 
Since Miller’s experiment, we know that reducing atmospheres are of great interest for 
prebiotic organic chemistry. Subjected to energetic particles bombardment (coming from 
solar radiations and Saturn’s magnetosphere), both hydrocarbons, nitriles (like HCN, a 
precursor of amino-acids) and organic aerosols are produced inside the atmosphere in 
notable amounts. 

For several years, at LISA, the atmospheric chemistry on Titan has been studied using 
laboratory simulation experiments. In order to mimic Titan’s atmosphere, we initiate a 
glow discharge in a N 2 /CH 4 (98/2) mixture at low temperature. Solid (tholins) and gaseous 
compounds including radicals and ions produced in the reactor are analyzed by different 
complementary analytical techniques. 

During the past decade, many experimental simulations have been carried out in vari- 
ous laboratories. Experimental conditions are too different: temperature, pressure, compo- 
sition of the initial gas mixture, energy sources, duration of experiment. The comparison 
between these experiments is then very difficult. The problem comes mainly from the lack 
of knowledge of the mechanisms leading to the formation of the products (gas and solid 

How to compare the reactor’s chemistry and Titan’s chemistry? In order to answer 
this question, we decided to deeply study the physical and chemical properties of the 
glow discharge. Pintassilgo et al. (1999) developed a kinetic model adapted to this type of 
experimental simulation in order to obtain the basic elementary mechanisms occurring in 
the discharge. We present here a coupling between the experimental simulation and this 
numerical model. This approach is used to calculate the electron energy distribution function 


J. Seckbach et al. (eds.), Life in the Universe, 287 - 291 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


(EEDF) and to determine the abundance of the species inside the plasma. This work allows 
us to have an insight into the fundamental mechanisms involved in these discharges and to 
go further on the study of the tholins’ formation, as well as their composition. 

2. Experimental Setup 

The experimental device is described in Coll et al. (1999). An improvement of the reactor 
allows to determine: 

• The species produced in-situ (in particular radicals and ions): an optical UV-VIS 
fiber with 200 p.m core diameter is placed in front of a fused silica window at the 
end of the reactor in order to collect the UV-VlS radiations. An optical system 
composed of two lenses is installed between the end of the optical fiber and the 
entry of the spectrometer in order to improve the light collection adapting the 
angular aperture of the optical fiber to the one of the spectrometer. The analysis 
is achieved with a monochromator (THR Jobin-Yvon) of Czerny-Turner type with 
a focal length of 1.5 m, offering a resolving power of 20000. Currently, the 230- 
550 nm range can be studied due to the combination of the fiber and photomultiplier 
band pass respectively for the shorter and the longer wavelengths. The spectrometer 
is controlled by a Lab VIEW (Natural Instrument) interface through an analogue 
output board (DDA06-Keithley) and a homemade electronics. 

• The reduced electric field E/Ng, where E is the electric field and Ng is the total 
neutral gas density (linked to the gas temperature Tg through the ideal gas law 
Ng = p/KTg). E is determined by measuring the difference in floating potential be- 
tween two electrostatic probes which are 15 cm apart and connected to a voltmeter 
through a high voltage probe. The gas temperature Tg is obtained from the rota- 
tional distribution of the ( Av = 0) transitions of the nitrogen second positive system 
N 2 (C^IIu) ^ N 2 (B^rig) at 337.1 nm, assuming that the rotational temperature is in 
equilibrium with the kinetic gas temperature, under our discharge conditions. The 
rotational temperature is determined by a least square procedure simultaneously 
on the five (Av = 0) transitions of the C-B transitions, from the comparison be- 
tween experimental and calculated spectra. The uncertainty on these calculations is 
estimated to be less than 10 %. 

3. Kinetic Model 

In the plasma, the electrons are accelerated by the electric field in the discharge. As the 
plasma is weakly ionized, electrons collide mainly with neutral species. It was previously 
shown, for instance in a N2-H2 mixture (Loureiro and Ricard, 1993), that the energy of 
electrons is mainly controlled by inelastic collisions with the molecular nitrogen ground state 
N 2 (Xi ) (Allan, 1985). The plasma is not in thermal equilibrium: the electron temperature 

is much greater than the gas temperature. At pressures typically below 20 mbar, the mean 
temperature of the electrons in these discharges is in the range 1-5 eV (leV~ 11000 K), 
and the most energetic electrons have an energy of the order of 10 eV. 


Theoretically, the reduced electric field E/Ng is determined from the requirement that, 
under steady-state conditions, the total ionization rate must compensate exactly the total 
loss rate due to ambipolar diffusion to the wall plus electron-ion recombination (Pintassilgo 
et al., 1999). This formulation ensures that we obtain the quasineutral condition in the glow 
discharge, i.e., the ion density is equal to the electron density. 

4. Results and Discussion 


Three kinds of species are studied: the radicals and ions which are produced inside the dis- 
charge and detected in-situ by the UV-visible spectrometer (Figure 1). By this last technique 
we have detected N^, CN, NH and CH; the solid compounds which are deposited on the 
walls of the reactor and analyzed in order to get their atomic composition (Bernard et al., 
2002); the produced gases which are collected at the end of the reactor and analyzed by IR 
spectrometry (Bernard et al., in press) and GC-MS (Coll et al., 1999). 


The aim of this work is to validate the kinetic model by experimental measurements. In 
Figure 2, a first comparison between theoretical and experimental E/Ng values is presented 
in pure nitrogen as a function of the value of the current. We can observe a good adequacy 
between the experimental and theoretical values. The next step will be to compare the data 
from a N 2 /CH 4 mixture as a function of current and as a function of pressure. 

Figure 1. UV-visible spectrum of a N 2 /CH 4 glow discharge (2% CH 4 in N 2 ). Pressure: 0.65 mbar; flow: 
1 200 seem; current: 40 mA; spectral resolution: 0.5 nm. 


Figure 2. Reduced electric field (E/Ng) as a function of current in pure nitrogen. The dots are the experimental 
data and the curve represents the theoretical model. 

5. Conclusion 

The coupling of an experiment with a kinetic model of a N2-CH4 glow discharge helps to 
understand the physical and chemical processes in the reactor during the glow discharge. 
We have validated the physical properties developed by the kinetic model in pure nitrogen 
cold plasma. 

The following step in the study of the discharge will be to determine the Electronic impact 
Energy Distribution Eunction (EEDF). Then, the rate coefficients for electronic reactions 
(ionization, dissociation, excitation) will be calculated using published values of reaction 
cross sections. As rate coefficients for neutral compounds are known, it will be possible to 
calculate, in steady state conditions, the density of the most important atoms, radicals and 
radiative states produced in the plasma. The experimental determination of the abundances 
of compounds and the atomic composition of solid products will constrain the current 
kinetic model by adding new detected species. The comparison between experimental and 
numerical data will enable us to predict and interpret results obtained by others in different 

Finally, this approach should contribute to help us to understand the results that will be 
obtained by the future Cassini-Huygens mission. 

This work has been supported by grants from the Action Thematique Innovante (A.T.I.) 
of the French Research Ministry, the French Space Agency, CNES and GDR Exobiologie. 

6. References 

Allan M. (1985) Excitation of vibrational levels up to v = 17 in N2 by electron impact in the 0-5 eV region. J. 
Phys. B:Mol. Phys. 18, 4511. 

Bernard J.-M., Coll P. and Raulin F. (2002) Variation of C/N and C/H ratios of Titan’s aerosols analogues. ESA 
SP-518, 623-625. 

Bernard J.-M., Coll P. and Raulin F. (2003) Experimental simulation of Titan’s atmosphere: detection of ammonia 
and ethylene oxide. Planet. Space Sc, in press. 


Coll R, Coscia D., Smith N. S., Gazeau M.-C., Ramirez S. I., Cernogora G., Israel G. and Raulin F. (1999) 
Experimental laboratory simulation of Titan’s atmosphere: aerosols and gas phase. Planet. Space Sci. 47 , 

Loureiro J. and Ricard A. (1993) Electron and vibrational kinetics in a N2-H2 glow discharge with applications 
to surface process. J. Rhys. D: Apll. Rhys. 26 , 163. 

Pintassilgo C. D., Loureiro J., Cernogora G. and Touzeau M. (1999) Methane decomposition and active nitrogen 
in a N 2 -CH 4 glow discharge at low pressures. Plasma sources Sci. Technol. 8 , 463^78. 



Group of Exobiology, Institute of Cytology, RAS 
Tikhoretsky Av., 4, St. Petersburg, 194064, Russia 

Accretion models of the Saturnian satellite suggest that heating released during late stages 
of its formation was sufficient to create a warm, dense atmosphere with mass at least 30 
times greater then the present value (Lunine and Stevemson, 1983) and large open ocean 
on its surface. Such juvenile Titan’s ocean could exist during period of 10* years. As the 
great part of the primordial Titan’s atmosphere could be supplied by comets during or after 
accretion, the composition of such atmosphere would have consisted of mostly H 2 O, N 2 , 
CO and CO 2 , since the cometary carbon appears concentrated in the form of CO (ranging 
from a few to 45% relative to water), CO 2 (~15%) and heavy organic. The mass of volatile 
acquired by Titan from comets would be expected to be ~ 10^°-10^^ g for CO and 10^°-10^^ 
g for N (Griffith and Zahnle, 1995). So we can see that the Titan’s primordial atmosphere 
could be warm, dense and consist of C 02 -(C 0 )-N 2 . 

The hrst stages of chemical evolution would have took place in these atmosphere and 
ocean under action of such energy sources as ultraviolet radiation, solar wind, galactic 
cosmic rays, magnetospheric plasma ion bombardment, electrical discharges and radiogenic 
heat. Recent attempts to establish a lower limit for the time required for emergence of life 
suggest that 10-100 million years was enough in case of Earth and the time of existence of 
the Titan’s juvenile ocean was enough for arising of the hrst protoliving objects. 

As the planet developed through time several energetic processes (irradiation, lightning, 
meteoritic and comet impacts) produced different forms of hxed nitrogen. All nitrogen could 
have been in the hxed form at the end of the planetary accretional period. Such scenario 
has been supposed by Mancinelli and McKay (1988) for the evolution of prebiotic nitrogen 
cycling on Earth, and the similar processes could be proposed in the case of the Saturn’s 
satellite. Hence, in the absence of a recycling mechanism dissolved NO 2 and NOj" would 
accumulate in the ocean. 

During the phase of cooling. Titan’s ocean was roofed over with icy crust. If life had 
originated by then, it could survive in some places up to the present (Eortes, 2000). On 
Earth microbial life exists in all locations where microbes can survive. In other case the 
variety of prebiotic processes can take place on Titan at present time. Many volatiles and 
inorganic salts were probably present in the primordial liquid layer and they must decrease 
the freezing temperature of the liquid at the stage of cooling. The compositions of the rich 
atmosphere, which is host to extensive organic photochemistry and internal liquid layer, 
must be very complex and Titan’s putative ocean might harbor life or complex prebiotic 


J. Seckbach et al. (eds.), Life in the Universe, 293 - 296 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


The most recent models of the Titan’s interior lead to the conclusion that a substantial 
liquid layer exists today under relatively thin ice cover inside the satellite (Lunine and 
Stivenson, 1987; Grasset and Sotin, 1996; Grasset et al, 2000). Lunin (1993) has shown 
that the underground ocean is the only structure that is consistent with all of the known 
constraints (chemical, tidal, ground-base radar and near-infrared observation) and Lorenz 
(2001) has found that internal oceans are mandated for the large icy satellites. Thermal 
evolution models also predict the existence of thick (~300 km) liquid layer with relatively 
thin (~80 km) ice cover (Grasset et al., 2000). Spohn and Schubert (2003) have shown that 
even radiogenic heating in a chondritic core may suffice to keep a water ocean inside large 
icy satellites. 

The present composition of the putative liquid layers of the ice satellites is probably very 
complex. Mass balance calculations modeled an extraction of elements into the aqueous 
phase from chondritic material show that Titan’s extensive subsurface ocean likely also 
contains dissolved salts from endogenic materials resembling to carbonaceous chondrite 
rocks incorporated into the satellite during its formation and released at the time of planetary 

There are three sources of organic carbon for Titan’s ocean: complex atmospheric 
chemistry (Clarke and Ferris, 1997), carbonaceous chondrites and cometary bodies, and 
seafloor hydrothermal systems. Since the light energy in the form of the solar radiation 
is not accessible in such conditions (the solar flux to Titan’s surface is ~1.1% from the 
Earth’s one) the chemical energy has to be the main source which drives the life and other 
disequilibrium processes. So, the initial components, such as NO^ , SO^” , COj” for the 
origin of lithoautotrophic processes could exist in the Titan’s putative ocean from the earlier 
stages of the satellite’s evolution and provide biologically useful electron donor-acceptor 
pairs in the upper layer where the temperature and pressure are not very hostile. Nitrate 
accumulated in the ocean at the first stage of atmosphere’s evolution would have allowed 
the first protobiosystems to use it as the primary source of energy. We would like to propose 
the idea that the first protoliving systems in Titan’s ocean could had internal energy source, 
namely, the chemical potential of an inorganic reaction - “Basic Reaction” (BR). 

There are some candidates on the role of BR. Electron acceptors such as N 03 ^, SO 4 , 
Ee^+,Mn4+, or CO 2 have to be coupled with the electron donors. Electron donors that may 
be important in such process include H 2 , CO, CH 4 , Ee^+, Mn^+, pyrite, sulfur compounds 
and organic material. Some of these molecules could be generated abiotically on the bottom 
of the internal ocean by the reaction of water with rocks of the silicate mantle and by the 
reaction of water with meteoritic components and others could be synthesized under the 
action of radiation. 

Eour energetic full operative biogeochemical cycles are possible inside Titan’s ocean, 
namely nitrogen (N-cycle), sulfur (S-cycle), iron (Ee-cycle) and carbon (C-cycle) and all 
of them could be connected each with other (Simakov, 2003). 

The basic reaction of nitrate reduction to dinitrogen is a more thermodynamically favor- 
able in the row of different inorganic substrates. The all gaseous nitrogen in the contemporary 
Titan’s atmosphere can be the product of this reaction (Simakov, 2000). Very interesting 
bacteria have been discovered recently which use ammonium as an inorganic electron 
donor for denitrification (Jetten et al., 1999). This reaction has a very favorable energetic 
(—357 kJ/mol). Hydroxylamine (NH 2 OH) and hydrazine (N 2 H 4 ) are formed as interme- 
diates and bicarbonate is the sole carbon source. This is the first case when hydrazine, 


a rocket fuel, is a free intermediate in any biological system. Both these components 
could be widespread in the Titan’s environments and could be used microorganisms for 
energy transduction and the buildup of an electrochemical gradient. And we can hypothe- 
size a start reaction as N2H4 ^ N2 which can evolve through NH2OH ^ N2H4 N2 to 
NO^ ^ NH2OH N2H4 ^ N2 at the rout of microbial evolution. 

Dissimilatory ferric iron-reducing and ferrous iron-oxidizing organisms also can form 
the basis for a closed ecosystem which gains energy through cyclic reduction and oxidation 
of iron minerals, sometime by -dependent way. Fe(III) oxyhydroxides are readily 
reduced with H2S, inorganic sulfides, elemental sulfur and various organic acids. On Earth 
microbial Fe(III) reduction is the major way of organic carbon oxidation in anaerobic 
environment. Microorganisms utilizing Fe(III) as an electron acceptor were discovered into 
mesobiotic marine and freshwater anoxic sediments and submerged soils. The denitrifying 
bacterium was isolated from the mud of Mariana Trench. It shows greater tolerance to low 
temperature and high hydrostatic pressure (50 MPa). Thermobiotic ecosystems also contain 
bacteria able to reduce Fe(III) with formate, lactate or molecular hydrogen. The production 
of reduced end products, e.g. Fe(II), FeS by Fe-reduction and H2S with such processes could 
resupply the basic reaction with reagents. Ferrous iron is oxidized chemically by a number 
of inorganic compounds, most notably molecular oxygen, manganese oxide (Mn02) and 
nitrate. So we can imagine a biogeochemical cycle for maintain of the primordial Titan’s 
ecosystem. The putative life inside Titan does not depend on solar energy and photosynthesis 
for its primary energy supply and it is essentially independent of the surface circumstances. 
There could be microorganisms having a great similarity with the last common ancestor 
(LCA) on Earth. 

Rich chemosynthetic ecosystems could be associated with methane clathrate areas on 
the icy bed. The cold methane vents induced by liquid methane could serve as a source 
for forming of the chemosynthetic ecosystems. These processes could involve a transfer 
of electrons from methane to sulfate or others electrons acceptors. The examples of such 
systems could be found around methane clathrate on the Earth’s sea bed. Some organisms 
are capable of disproportioning of methanol, methylamines or methylsulphides to methane 
and carbon dioxide, oxidizing -CFI3 groups to CO2 anaerobically. Microbial consortia based 
on anaerobic oxidation of methane coupled to sulfate reduction can support other microbial 
communities by generating of substantial biomass accumulation derived from methane. 

Along with the upper layer of the internal water ocean when a temperature and pressure 
are suitable for living processes there are some additional appropriate sites for biological 
and/or prebiological activity at present day (Simakov, 2001 ): ( 1 ) water pockets and liquid 
veins inside icy layer; ( 2 ) the places of cryogenic volcanism; ( 3 ) macro-, mini- and micro- 
caves in the icy layer connecting with cry o volcanic processes; ( 4 ) the brine-filled cracks 
in icy crust caused by tidal forces; ( 5 ) liquid water pools on the surface originated from 
meteoritic strikes; (6) the sites of hydrothermal activity on the bottom of the ocean. 

The environments mentioned above indicate that all conditions capable of supporting 
life are possible on Titan. All requirements needed for exobiology — liquid water which 
exists within long geological period, complex organic and inorganic chemistry and energy 
sources for support of biological processes are on Saturnian moon. On Earth life exists in 
all niches where water exists in liquid form for at least a portion of the year. Sub glacial life 
may be widespread among such planetary bodies as Jovanian and Saturnian satellites and 
satellites of others giant planets, detected in our Galaxy at last decade (Perryman, 2000 ). 


The low temperature hypersaline brines have been proposed as habitat for microbial com- 
munities on Mars. The existence of rich atmosphere is the main difference from the Jupiter’s 
moons. This atmosphere could supply the large quantity of different organic compounds to 
putative ocean. There are some possible mechanisms for extensive, intimate interaction of 
a liquid water ocean with the surface of the ice crust. Titan provides also insights regarding 
the geological and biological evolution of early Earth during ice-covered phase. There is 
a huge deficiency of carbon in the contemporary environment and this disappeared carbon 
could be contained as biomass and dissolved organic carbon in the putative ocean. Possible 
metabolic processes, such as nitrate/nitrite reduction, sulfate reduction and methanogenesis 
could be suggested for Titan. Nitrate and sulfate could be predominant forms of N and S in 
the ocean and nitrate and/or sulfate reduction would have been potential sources of energy 
for primitive life forms. Given the possibility that organic compounds may be widespread 
in the ocean from synthesis within hydrothermal systems, derived from atmospheric chem- 
istry and delivered by comets and meteorites these putative nitrate and sulfate reducers may 
have been either heterotrophic or autotrophic. Furthermore, at the presence of substantial 
amount of methane the methanogenesis along with methanotrops also have been energeti- 
cally favorable. Excreted products of the primary chemoautotrophic organisms could serve 
as a source for other types of microorganisms (heterotrophes) as it has been proposed for 


Clarke, D.W. and Ferris, J.P. (1997) Chemical evolution on Titan: comparisons to the prebiotic Earth. Orig. Life 
Evol. Biosphere, 27, 225-248. 

Fortes, A.D. (2000) Exobiological implications of a possible ammonia-water ocean inside Titan. Icarus, 146, 

Grasset, O. and Sotin, C. (1996) The cooling rate of a liquid shell in Titan’s interior. Icarus, 123, 101-1 12. 

Grasset, O. et al. (2000) On the internal structure and dynamics of Titan. Planet. Space Sci., 48, 617-636. 

Griffith, A.C. and Zahnle, K., (1995) Influx of cometary volatiles to planetary moons: The atmospheres of 1000 
possible Titans. J. Geophys. Res., 100, 16907-16922. 

Jetten, M.S.M. et al (1999) The anaerobic oxidation of ammonium. FEMS Microbiol. Rev., 22, 421^37. 

Lorenz, R.D. (2001) 32nd Lunar Planet. Sci. Conf. Abstract #1 160. 

Lunine, J.I. (1993) Does Titan have an ocean? A review of current understanding of Titan’s surface. Rev. Geophys., 
31, 133-149. 

Lunine, J., Stevenson, D. (1983) Formation of the Galilean satellites in a gaseous nebula. Icarus, 52, 14-38. 

Lunine, J.I. and Stevenson, D. (1987) Clathrate and ammonia hydrate at high pressure: Application to the origin 
of methane on Titan. Icarus, 70, 61-77. 

Mancinelli, R., McKay, C. (1988) The evolution of nitrogen cycling. Orig. Life Evol. Biosphere, 18, 311-325. 

Perryman, M.A.C. (2000) Extra-solar planets. Rep. Progr. Phys., 63, 1209-1272. 

Pizzik, A.J. and Sommer, S.E. (1981) Sedimentary iron monosulfides: Kinetics and mechanism of formation. 
Geochim. Cosmochim. Acta, 45, 687—689. 

Simakov, M.B. (2000) Dinitrogen as a possible biomarker for exobiology: The case of Titan. In: G. A. Lemarchand 
and K. J. Meech (eds.) Bioastronomy ’99: A new era in bioastronomy, Sheridan Books, pp. 333-338. 

Simakov, M.B. (2001) The possible sites for exobiological activity on Titan. In: Proc. First European Workshop 
on Exo/Astro-Biology, Frascati, 21-23, May 2001, pp. 21 1-214. 

Simakov, M.B. (2003) Possible biogeochemical cycles on Titan. In press 

Spohn, T. and Schubert, G. (2003) Oceans in the icy Galilean satellites of Jupiter? Icarus, 161, 456-^67. 

XL The Search for Extraterrestrial 
Intelligence (SETI) 


2003 Present Activities and Future 




^CNR- Istituto di Radioastronomia, — Via Fiorentina, 40060 
Villafontana,-Bo-Italy; ^Osservatorio Astronomico di Torino Italy; ^Centro 
di Astrodinamica “C. Colombo”, Via Martorelli 43, 10155 To Italy; -CNR 
Istuto di Fisica dello Spazio InterpL, Via Fosso Del Cavaliere, 00133 
Roma, Italy; ^ Osservatorio Astronomico di Cagliari, Via salita dei Pini, 
Cagliari, Italy. 

Abstract. Observation activities within the Seti program have started at the Medicina radiote- 
lescope (near Bologna — Italy-) since March 1998. An ultra high frequency resolution Serendip 
IV spectrometer module, in a 4 million channels configuration, was used. Observations with 
the Serendip IV spectrometer connected in piggyback mode have been carried out so far at the 
32-mt VLBI dish antenna in the microwaves astronomical bands. In order to increase the de- 
tection possibilities, a more flexible version of the data post processing procedure (SALVE II) 
and a quite new KLT (Karhunen Loeve Transform) for data detection have been introduced. 
The final tests of such a KLT have been carried out with an expandable fast Mercury Altivec 
multinode CPUs cluster. This is planned to operate in parallel to the already existing Serendip 
IV high-resolution spectrometer. 

I. Introduction 

There are at least 10^^ stars in the universe. The nearest 10^' are organized into the Milky 
Way, a lens shaped sistem of stars, gas, dust and dark matter wich is about 100.000 ly in 
diameter. This is our galaxy: the “island” where we live in the Universe! A fundamental 
question has arisen, from the ancient greek phylosophers up to the present scientists: are 
we the only intelligent inhabitants of this boundless island? 

One of the way to answer this question is to search for some manifestation of a distant 
technology as, for instance, radio signals. The Seti program is aimed to the search for 
radio signals coming from the outer space and generated by extraterrestrial technological 

The Italian Institute of Radioastronomy of the Istituto Nazionale di Astrofisica, has been 
directly involved in Seti activities since March 98 when a Serendip IV, Werthimer (1996), 
system, an ultra high frequency resolution FFT (Fast Fourier Transform) based spectrum 
analyzer, was installed at the Medicina 32 m dish VLBI antenna (Fig. I). 


J. Seckbach et al. (eds.), Life in the Universe, 299 - 302 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


Figure 1. View of the Medicina 32 m dish. 

Since it operates in parallel, Werthimer (2000), to the ongoing observing programsat 
the 32 m VLBI dish, dedicated time for this particular radio signals search is not required. 
This approach drammatically reduces the cost of the program. While the radioastronomers 
use the radiotelescope, the Serendip IV searches for a CW signal at the same frequency and 
position in the sky as programmed in the observing schedule. In this way, the Seti search 
exploits the 100% of the antenna working time without any additional charge and, at the 
same time, takes under control the RFIs (Radio Frequency Interferences). 

2. Seti-Italia: Present Situation 

We tested the system during summer 1998 when the european VLBI network was engaged 
(under NASA request) to check some Mars Global Surveyor orbit parameters: the system 
post processing software provided an alarm due to the frequency shifted (Doppler effect) 
radio carrier coming from the spacecraft. 

So far, the total estimated observed time, since the installation of the system, is summed 
up in the following table. 

We haven’t received any evidence of ETI radio signals during this observation time. We 
detected only man made radio interference (RFIs). Unfortunately the RFIs situation in Italy 
is continuously getting worse and an increasing effort is devoted to the radio astronomical 
frequency bands protection. 

At present the instruments potentially involved in this program are: 


Single Dish 





Calibration & Tests 















510 days 

400 days 

100 days 

210 days 

150 days 

~40 days 

1. The Northern Cross Radiotelescope 564 x 640 mt (Medicina -Bo-): a very large 
transit radiotelescope able to cover the whole northern hemisphere (0° H- 90°) with 
30.000 sqm of collecting area. 

2. The 32 mt VLBI dish (Medicina -Bo-) 

3. The 32 mt VLBI dish (Noto -Sr- equipped with a new active mirror surface. 

• The SRT 64 mt dish (under contractions near Cagliari, Sardinia Island) equipped 
with an active surface mirror allowing to work up to 100 GHz with a very good 
efficiency. It will work from 300 MHz up to 100 GHz 

A new release of SALVE (SALVE 2) (salve in Italian means “hello”) for Serendip IV 
data post processing procedures, based on the Hough transform, Monari (2000), for pattern 
recognition, was installed and tested. This is a very useful utility, especially exploited during 
the very crucial dopplered line detection algorithms post processing phase. 

3. New Developmente in Data Acquisition 

A prototype (MED ALT- 1 ) of a fast vector multinode (Motorola 7400) system was assembled 
to test a Karhunen Loeve Transform (KLT) fast algorithm. The prototype is equipped with 
a double 12 hit 41 Ms/s A/D converter (Pentec™) triggered through an ad hoc designed 
programmable Direct Digital Synthesiser (DDS) clock generator. Data are moved from the 
A/Ds hoard to the CPUs carrier board (each VME carrier board can house two piggy-hack 
modules with 2 CPUs each) through a EPDP bus. 

It is well known the advantage obtained by the application of the KLT, Dixon (1993), 
instead of the EFT, in searching for any kind of signal in a radio band. The EFT always 
uses cos and sin as base functions and, in addition, it considers the signals periodic as the 
length of the data acquisition window. In this way it works well with monochromatic signals 
but not so properly with more complex radio signals. The KLT extracts the base functions 
from the signal itself and, then, works properly with any kind of signals (of course for a 
monochromatic signal it hnds cos and sin base functions as the EFT). For this reason the KLT 
is a very suitable key transform, Maccone ( 1 994), able to “understand” whether or not a radio 
band, supplied by the radio telescope, contains any kind of modulated signals, Maccone 
(2003). If an extraterrestrial technological civilization exists and communicates on its planet 
with radio waves, we cannot know in advance which radio signals they are spreading out 


the space (unless they intentionally transmit a CW signal). In this situation the KLT is 
the more suitable transform to detect unknown radio signal. The fast approach to the KLT 
(eigenvalues and eigenvectors computation) we worked on, is based on the following steps: 

- N points data acquisition 

- N points autocorrelation vector computation 

- Autocorrelation matrix computation 

- Arnoldi/Lanczos factorisation 

- Givens Rotation (Eigenvalues approximation) 

Assuming that our radio band will not contain more than 40 signals (searched signal + 
RFIs), we compute only these first 40 eigenvalues (in practice the first more important 
eigenvalues) and not all the N eigenvalues. For instance, operating with N = 1024 points, 
10 MHz input bandwidth and using only one processor, it takes about 1.5 sec to compute 
the first 40 eigenvalues. 

4. Summary 

SETI observations have started at the Medicina radio telescopes since March 98. No evi- 
dence of ETI signals came out from our SETI activity so far. It is anyway necessary to go 
ahead with SETI observations because with the same high-resolution back end, the man- 
made radio interference can be effectively taken under control. A fast approach to the KLT 
computation (used as a detection tool in SETI), has been tested with good results, anyway 
a more detailed investigations on this transform needs to be done. 

5. References 

Dixon, S. R., Klein C. A. (1993) On the detection of unknow signals. The Third decennial US-USSR Conference 
on Seti ASP Conference series, Vol 47, 1993 Pag. 129-140. 

Maccone C. (1994) Telecommunications, KLT and Relativity, Volume 1, IPl Press, Colorado Springs, CO, 1994, 
ISBN #1-880930-04-8. 

Maccone C. (2003) Innovative SETI by the KLT”, Pesek Lecture 2003, paper # IAA.9. 1 .01 presented at the 2003 
lAF Bremen International Astronautical Congress. 

Monari J., Montebugnoli S., Ravaglia F., Cecchi M. (2000), SALVE, New Era in Bioastronomy ASP Conference 
Series, Vol. 213, 479^83. 

Werthimer D., Boyer S., David N., Donnely C., Cobb I., Lampton M., Aireau S. (1996) The Berkeley SETI 
Program Serendip IV instrumentation. Proceedings of 5th International Conference on Bioastronomy lAU 
Colloquium, No 161, 683-688. 

Werthimer D., Boyer S., Cobb J., Lebofsky M., Lampton M. (2000) The Serendip IV Arecibo Sky Survey, A New 
Era in Bioastronomy ASP Conference Series, Vol. 213, 479^83. 



Alenia Spazio S.p.A., Strada Antica di Collegno, 253, 
Torino (TO) 10146 — Italy 

1. Introduction 

The “Lunar Farside Radio Lab” Study of the International Academy of Astronautics (lAA), 
started in 1998 by late French astronomer Jean Heidmann (1923-2000), underwent sub- 
stantial extensions and revisions since its coordination was taken up by this author. These 
modifications can be summarized as follows: 

1) The goal of the Study was enlarged so as to encompass the whole of radio astron- 
omy, rather than just SETI. 

2) It was stressed that, from the Lunar Farside, one can detect radio frequencies lower 
than 15 MHz (i.e. wavelenghts longer than 20 m) impossible to detect from the 
Earth because of the blocking effect of the Earth’s ionosphere. By detecting these 
radio waves from the Earside of the Moon, new discoveries should be expected 
especially in the fields of Cosmology and Stellar Astrophysics. 

3) Lunar Earside Crater Saha, initially selected by Heidmann to host a radiotelescope, 
was replaced by Lunar Earside Crater Daedalus, located just at the Earth’s Antipode 
on the Moon Earside. In fact, Daedalus is much more shielded than “Saha”, not 
only against the radiation emitted by any future spacecraft orbiting the Earth at 
distances higher than the geostationary orbit, but even against the radiation emitted 
by the future Space Stations located at the triangular Lagrangian points LA and 
L5 of the Earth-Moon system, as proposed long ago by Jerry O’Neill of Princeton 

4) Four different scenario were envisaged for the relevant space mission, dubbed 

a) Cheapest and easiest of all, just a spacecraft orbiting the Moon in its equatorial 
plane and carrying a 3-meter inflatable antenna detecting radio signals from 
the Universe when in the Shadow of the Earth, and downloading the data when 
above the Nearside. 

b) More expensive but not-so-hard-to-make: just the same as a) but with two or 
more spacecrafts, so as to create and interferometric Array in orbit around 
the Moon. 


J. Seckbach et al. (eds.), Life in the Universe, 303 - 306 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


c) More expensive still and hard-to-make, landing a Phased Array inside Daedalus 
and keeping the link with the Earth by a relay satellite in circular orbit around 
the Moon. 

d) Very expensive and difficult: the same as in b) but with the goal of creating of 
an Array of Phased Arrays inside Daedalus. Much robotic work would then be 
requested plus one or more relay satellites orbiting the Moon. 

Finally, legal protection of Daedalus from radio-pollution was sought, initially by virtue 
of the IISL. This is a very important issue, that should be soon presented to the United 
Nations Committee for the Peaceful Use of Outer Space. The “Lunar Farside Radio Lab” 
Study of the lAA should be published in 2004. The current status and future prospects of 
this “Cosmic Study” of the lAA are explained and justihed in this paper. 

2. Terminal Longitude \ on the Moon Farside for Radio Waves Emitted by 
Telecommunication Satellites in Orbit Around the Earth 

In this section we just mention, without mathematical proof, an important equation, vital 
to select any RFI-free Moon Farside Base. We want to compute the small angle a (see 
Figure 1) beyond the limb (the limb is the meridian having longitude 90° E on the Moon) 
where the radio waves coming from telecommunications satellites in circular orbit around 
the Earth still reach, i.e. they become tangent to the Moon’s spherical body. The new angle 
X. = a -4- 90° we shall call “terminal longitude” of these radio waves. In practice, no radio 
wave from telecom satellites can hit the Moon surface at longitudes higher than this terminal 
longitude X. Then, X turns out to be given by the equation 

X (R) = atan 

^ ^Moon 

' ^\arth-Moon ~ {R ~ Rmooii) 


2 ' 

Here the independent variable R can range only between 0 and the maximum value that 
does not make the above radical become negative, that is 0 < R < D Earth- Moon + Rmooh ■ 

3. Selecting Crater Daedalus at 180° E 

The Committee claims that the time will come when commercial wars among the big 
industrial trusts running the telecommunications business by satellites will lead them to 

Telecom Satellite Orbit 

Figure 1. The simple geometry defining the “Terminal Longitude, X” on the Farside of the Moon, where radio 
waves emitted by telecom satellites circling the Earth at a radius R are grazing the Moon surface. 


grab more and more space around the Earth, pushing their satellites into orbits with apogee 
much higher than the geostationary one, with the result that crater Saha will be blinded as 
soon as a company decides to go higher than the geostationary orbit. The last remark is 
important for Bioastronomers. If we, the supporters of Bioastronomy, bet everything on a 
SETI and Bioastronomy Base located at Saha, then we may loose everything pretty soon! A 
“safer” crater must be selected further East along the Moon equator. How much further 
East? The answer if given by the above equation for X. 

Next we are now led to wonder: what is the Moon Farside terminal longitude corre- 
sponding to the distance of the nearest Lagrangian point, LI? The answer is given by the 
equation upon replacing R — 323050 km, and the result is X = 154.359°. In words, this 
means the following basic, new result: the Moon Earside Sector in between 154.359 E and 
154.359 W will never be blinded by REl coming from satellites orbiting the Earth alone. 

In other words still, the limit of the blinded longitude as a function of the satellite’s 
orbital radius around the Earth is 180° (E and W longitudes just coincide at this meridian, 
corresponding to the “change-of-date line” on Earth). But this is the antipode to Earth on 
the Moon surface, that is the point exactly opposite to the Earth direction on the other side 
of the Moon. And our mathematical theorem simply proves that the antipode is the most 
shielded point on the Moon surface from radio waves coming from the Earth. An intuitive 
and obvious result, really. 

So, where are we going to locate our SETI Farside Moon base? Just take a map of 
the Moon Farside and look. One notices that the antipode’s region (at the crossing of the 
central meridian and of the top parallel in the figure) is too a rugged region to establish a 
Moon base. Just about 5° South along the 180° meridian, however, one finds a large crater 
about 80 km in diameter, just like Saha. This crater is called Daedalus. So, the Committee 
proposes to establish the first REl-free base on the Moon just inside crater Daedalus, the 
most shielded crater of all on the Moon from Earth-made radio pollution! 

4. The Committee’s Vision of the Moon Farside for RFI-free Searches 

Let us replace the value of X = 154.359° by the simpler value of X = 150°. This matches 
also perfectly with the need for having the borders of the Pristine Sector making angles 
orthogonal to the directions of L4 and L5. The result is this vision of the Farside: 

1) The Nearside of the Moon is left totally free to activities of all kinds: scientific, 
commercial and industrial. 

2) The Farside of the Moon is divided into three thirds, namely three sectors covering 
60° in longitude each, out of which: 

a) The Eastern Sector, in between 90° E and 150° E, can be used for installation 
of radio devices, but only under the control of the International Telecommuni- 
cations Union (ITU-regime). 

b) The Central Sector, in between 150° E and 150° W, must be kept totally free 
from human exploitation, namely it is kept in its “pristine” radio environment 
totally free from man-made RFI. This Sector is where crater Daedalus is, a 
~80 km crater located in between 177° E and 179° W and around 5° of latitude 
South. At the moment, the Committee is not aware of how high is the circular 
rim surrounding Daedalus. 


c) The Western Sector, in between 90° W and 150° W, can be used for installation 
of radio devices, but only under the control of the International Telecommuni- 
cations Union (ITU-regime). Also: 

1) The Eastern Sector is exactly opposite to the direction of the Lagrangian point 
L4, and so the body of the Moon completely shields the Eastern Sector from REI 
produced at L4. Thus, L4 is fully “colonizable”. 

2) The Western Sector is exactly opposite to the direction of the Lagrangian point 
L5, and so the body of the Moon completely shields the Western Sector from REI 
produced at L5. Thus, L5 is fully “colonizable” in the Committee’s vision, whereas 
it was not so in Heidmann’s vision. In other words, the Committee’s vision achieves 
the/w/Z bilateral symmetry of the vision itself around the plane passing through the 
Earth-Moon axis and orthogonal to the Moon’s orbital plane. 

3) Of course, L2 may not be utilized at all, as it faces crater Daedalus just at the 
latter’s zenith. Any RFI-producing device located at L2 would flood the whole of 
the Farside, and must be ruled out. L2, however, is the only Lagrangian point to 
be kept free, out of the five located in the Earth-Moon system. Finally, L2 is not 
visible from the Earth since shielded by the Moon’s body, what calls for “leaving 
L2 alone”! 

5. References 

Heidmann J. (1994), Saha Crater: a candidate for a SETI Lunar base, Academy Transactions Note, Acta Astro- 
nautica, 32, 471^72. 

Heidmann J. (2000) Sharing the Moon by Thirds: An Extended Saha Crater Proposal. Advances in Space Research. 
26, 371-375. 

Heidmann J. (2000), Recent Progress on Lunar Farside Crater Saha Proposal, Acta Astronautica, 46, 661-665. 

Maccone C. (2001), Searching for Bioastronomical Signals from the Farside of the Moon, First European Workshop 
on Exo/Astrobiology, ESRIN, Frascati, Italy, 21-23 May 2001. ESA SP-496, 277-280. 

Maccone C. (2001), The Lunar SETI Cosmic Study of lAA: Current Status and Perspectives, IAA-Ol-IAA.9.1.05, 
52”‘^ Int. Astronaut. Congress., 1-5 Oct. 2001. 

Maccone C. (2002), Planetary Defense and RFI-Free Radioastronomy from the Farside of the Moon: A Unified 
Vision, Acta Astronautica, 50, 185-199. 

Maccone C. (2002), The Lunar Farside Radio Lab Study of lAA, IAA-02-IAA.9.1.4, World Space Congress - 
2002, held in Houston, Texas, 10-19 October 2002. 

Maccone C. (2003), The Quiet Cone Above the Farside of the Moon, Acta Astronautica, 53, 65-70. 




^Advisor to the United Nations Secretary General, New York, USA; 
^Department of Mechanics, Politecnico di Torino, Torino, Italy; 
^Department of Physics, University of Torino, Torino, Italy; and 
^Non Governmental Peace Strategies Project — Geneve, Switzerland 

I. Introduction 

Since the mid-1980s the SETI Committee of the International Academy of Astronautics 
started a study on the attitude researchers in the field should take when (and if) a serious 
candidate signal is detected. The results were published in a number of papers printed in a 
special Issue of Acta Astronautica (Tarter and Michaud, 1990) under the heading of SETI 
Post Detection Protocols. This research work was later at the base of a document with 
the formal title Declaration of Principles Concerning Activities Following the Detection of 
Extraterrestrial Intelligence. 

At point 8 of this Declaration the possibility of broadcasting an answer is dealt with. 
This issue was first considered by Ney (Ney, 1985) and Goodman (Goodman 1990), who 
suggested the formalization of ad hoc International Agreements. In a subsequent paper 
Goldsmith (Goldsmith 1990) suggested that the International Astronautical Federation and 
the International Astronomical Union should give way to a Committee aimed to create an 
international agreement on how to formulate an answer from planet Earth to a confirmed 
detection of an alien message. 

Michael Michaud, president of a subcommittee of the SETI Committee of the Inter- 
national Academy of Astronautics, suggested that future projects related to the issue of 
sending radio (or optical) signals towards the outer space should be discussed in an inter- 
national forum. Such a document was approved by the Board of Trustees of the Academy, 
and become a formal Position Paper (Tarter and Michaud, 1990). It was also approved 
by the Board of Directors of the International Institute of Space Law. It was also sug- 
gested that this document should be submitted to the COPUOS. In 1996 John Billingham, 
chairman of the SETI Committee of the International Academy of Astronautics, published 
this document with the title of Post-Detection SETI Protocol. In various points of this 
document there is an explicit reference to the United Nations. In particolar, it is stated 
that a the Secretary General of the U.N. should be immediately informed of a confirmed 


J. Seckbach et al. (eds.), Life in the Universe, 307 - 309 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


In the Draft Declaration of Principles Concerning the Sending of Communications 
to Extraterrestrial Intelligence, included in the Protocols it is stated that the problem od 
answering should be discussed by the COPUOS and the General Assembly of the UN. The 
UN should base its decisions on the exerience and knowledge of scientists and experts. The 
final decision on how to deal the matter of the answer should be entrusted to the Secretary 
General, who is the only authority who has the duty of speaking for humankind. 

2. Proposal 

The present proposal, formulated by the Italian SETI Study Center, is aimed to create 
an international advisory board aimed to assist the UN Secretay General in the task of 
representing humankind in the event of a contact with alien civilizations. It is articulated in 
the following points: 

1 . The preparation of an ad hoc study on SETI by an international panel of experts 
of various disciplines for the United Nations, addressed to the Secretary General. 
This study should cover all possible aspects (including scientific, philosophical, 
social, media, intelligence and security aspects) and be updated on a bi-annual 

2. The identification and formalization of the role of the United Nations Secretary 
General and his International Advisory Board in the functions of decision- 
making, management of communication with the international media system 
vis-a-vis the possible detection of artificial signals of proven extraterrestrial 

3. To create an effective, temporary board for the United Nations Secretary General, 
with information and situation support capabilities for SETI. It should act as the 
United Nations Secretary General’s situation support staff in instances of extrater- 
restrial signal detection and, in particular, to assist him in the decision-making 
process upon successful detection of such signals. 

The board will, in effect, develop, and make official, the contents of the SETI Post- 
Detection Protocols, expanding its activity to managing communication of any signal detec- 
tion to the international media system. It should be composed of experts with internationally 
recognized credibility and competence in the following areas: Astrophysics and Cosmol- 
ogy, Bioastronomy, Radioastronomy, Astronautics and Space Exploration, Mathematics 
and Informatics, International Space Law, Social Sciences, International Relationships, 
Philosophy of Science, Religious Aspects, Mass Media, Intelligence and Military Aspects. 
The International Advisory Board should meet every two years to update and follow-up on 
current needs. 

The funds required to create, maintain and support the activities of the international 
advisory board will not be provided by the United Nations but rather will be raised in 
the private sector, through various foundations, companies and associations with adequate 
international standing. 


3. References 

Goldsmith, D., (1990), Who Will Speak For Earth?, Acta Astronautica, Vol. 21, No. 2, 149-151. 

Goodman, A.E., (1990), Diplomacy and the Search for Extraterrestrial Intelligence, Acta Astronautica, 21 , No. 2, 

Ney, P. (1985), An Extraterrestrial Contact Treaty?, JBIS, 38, 521-522. 

Tarter J.C. and Michaud M.A. (Eds.) (1990), SETI Post-Detection Protocol, Acta Astronautica, 21 , No. 2. 



Department of Mechanics, Politecnico di Torino, 
C. Duca degli Abruzzi 24, 10129, Torino, Italy 

Abstract. Many papers have been published in the past on the issue of the possible existence of 
humanoid extraterrestrial intelligence (ETI) and the prevalent opinion is now that the humanoid 
form is rather an exception than a rule. The aim of the present paper is to consider an intelligent 
being as a sort of machine which has to perform a number of tasks, and to discuss whether the 
humanoid form is dictated by them. While not intending to supply answers but only to formulate 
some problems, it is suggested that, although there is no doubt that a close relationship between 
our layout and our essence of intelligent beings exists, this is not enough to support any claim 
that the humanoid form is prevalent. 

I. Introduction 

The predominance of the humanoids, i.e. whether extraterrestrial intelligent living beings 
(ETls) may be similar, in a general sense, to humans is a very old issue; the first to take a firm 
stance on the subject was Galileo (Galilei, 1613), who stated that living beings may exist 
on the Moon or on other planets, but that their characteristics must be not only different 
from those of the beings on the Earth, but also from what our wildest imagination can 
produce. Nevertheless when the idea of ETIs became popular it was very often embodied 
in humanoid form; the aliens of early science fiction novels were humanoid, as well as 
almost all of those starring in science fiction moves and the popular image of aliens is that 
of humanoids. However, ETIs with different body shapes and even based on a completely 
different biology have been described (Pickover, 1999). 

The very concept of ‘humanoid’ can refer either to an ETI with a body similar to that 
of humans, or a living being with any body shape but with an intelligence comparable with 
human intelligence both in quantity and quality. In humans intelligence goes together with 
consciousness and we take usually for granted that this is the case for all intelligent beings, 
but this is another point which can be debated. 

Since most ETIs are assumed to be much older than us, by million (or billion) years, 
the very assumption that humanoid (in any sense) ETIs exist means that this is the ultimate 
form toward which evolution tends. There is no doubt that the human body and intelligence 
are very successful products of the evolutionary pressures on this planet. It can be argued 
that physical evolution may stop with the birth of intelligence and cultural evolution takes 
its place. A conscious species which attribute a large value to the life of individuals tends to 


J. Seckbach et al. (eds.), Life in the Universe, 311 - 315 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


oppose with increasing success natural selection as soon as science and technology advance; 
medicine, in its effort to grant a life as healthy and normal as possible to all individuals, 
independently from their fitness in a Darwinian sense, is a long battle against natural se- 
lection. But medicine and biology could have also another task: not to stop evolution, but 
to facilitate it producing favourable mutations. There is a general agreement to consider 
ethically unacceptable this last issue. 

These considerations apply to all ETIs, who could behave in a different way facing this 
ethical choice. It then seems that we could find two types of ETIs: either species undergoing 
very little physical changes even in long times, and others which design their bodies using 
genetic engineering and eventually differentiate in many species to adapt themselves to 
different environments, different tasks or even just personal taste. 

The aim of the present paper is to present some considerations on the human body as a 
peculiar machine designed (or better evolved) for a set of tasks and on its intelligence as the 
control program of such a machine. Note that the term evolution has been used to describe 
the advance of technology (Basalla, G. 1989). 

2. Mobility and Manipulation 

Mobility of a living being is strictly linked with how it gets food and energy. Autotrophic 
beings may not need any sort of mobility, while heterotrophic ones, and particularly preda- 
tors (Endler 1993, Cockell and Lee, 2002), usually need to move to obtain food. Large 
animals either are supported on a solid surface, float in a fluid under the effect of hydro- 
static (fluidostatic) forces or fly using aerodynamic (fluid-dynamic) forces (Azuma, 1989). 
Very small beings may use other supporting mechanisms, like surface tension (e.g. insects 
of the order Hemiptera), molecular interactions, etc. Since it is likely that an intelligent 
being has a minimum size larger than allowing to use these mechanisms, they will not be 
considered. Other solutions, like magnetic levitation or jets, are conceivable but are quite 
hypothetical and will not be considered. 

On the Earth most animals moving on a solid surface use some sort of legs. Evolution 
is characterized by a gradual reduction of the number of the legs and with the terrestrial 
vertebrates their number reduced to four. A high number of legs, together with a low position 
of the center of mass allows the animal to remain easily in static equilibrium during all phases 
of walking. In general, the larger is the animal and the lower is the gravity of the planet, the 
easier is to remain in equilibrium on a small number of legs, in the sense that the response 
of the nervous system to avoid falling down may be less quick. From this point of view low 
gravity simplify all operations related to motion. 

On the other side, a maximum walking speed exists for any animal; then a change of gait 
and the transition from walking to running or jumping (Cavagna et al., 1998, Minetti, 2001) 
is needed. This speed is larger for taller animals and higher gravity. Since a high speed is 
in general an important factor in natural selection, there is a strong incentive to shift from 
walking (a sequel of static equilibrium positions) to running (which includes positions in 
which static equilibrium is not guaranteed). Large animals, possibly with a smaller number 
of legs, may have then an advantage, and bipeds are a very good configuration for beings 
having an adequate control system. 


For what we can infer from the case of the Earth, the rise of intelligence and conscious- 
ness is linked to the development of the nervous system. Neurogenesis seems to be linked 
with multicellularity, and as soon as the nervous system started to become complex also 
the process of encephalization started. To reach a complexity sufficient for intelligence and 
consciousness, the nervous system must have a minimum size. 

The energy consumed by the human brain is quite large: it constitutes only 2% of the 
weight of the body, but it consumes 20% of energy. From an energetic viewpoint it seems 
that an intelligent species needs to be hetero trophic, possibly high in the food chain, since it 
needs a much energetic food which can be assimilated quickly. These considerations would 
indicate that ETIs should be, at least at the beginning, predators. Moreover, it is a common 
opinion that the difficulties experienced by a generalist animal for hunting had a positive 
effect on the development of intelligence (Leakey, 2000). 

On the Earth, hominids started developing technology when still their consciousness 
and intelligence were far less advanced than those characterising Homo Sapiens Sapiens. 
If an intelligent being is a ‘generalist’ animal, this is mostly due to the fact that he is able 
to use objects that increase the potentialities of its body, working like prostheses: what 
other species accomplish by slowly modifying their body, intelligent life forms obtain in an 
incomparably shorter time by implementing purposely designed objects (Righetto, 2000). 
Technology is a consequence of the development of intelligence, but causes itself problems 
which require an increase of the size of the brain and then a development of intelligence. As 
a consequence, intelligent beings need to have a technology and some manipulatory organs, 
arms and hands (at least in the sense used in robotics). 

ETIs can thus be expected to have some sort of locomotory and manipulatory organs; 
the latter being best derived from locomotion organs like legs. The humanoid layout with 
two arms and two legs seems to be optimal. 

3. Symmetry 

The general body plan of humanoids seems to be very suitable for an intelligent being, and 
the development of intelligence may well have been favoured by the challenges caused by 
the humanoid form. In particular, a biped layout with erect stance seems to be a logical con- 
sequence of an intelligent being with manipulatory appendages deriving from quadrupeds 
and carrying a heavy brain-case with many sensory organs at the front end. But such con- 
figuration is very demanding on the equilibrium organs and on the brain to obtain a sure 
and fast biped walk and run. Only with Homo (Abilis and then Erectus) these features could 
be obtained, while earlier hominids were much apelike (even early members of the Homo 
genus were more primitive from this viewpoint). 

However, these considerations are not sufficient to state that it is likely that ETIs have 
a body form resembling humans. On the Earth all terrestrial and many sea animals have a 
bilateral symmetry, at least in the exterior body shape, with an even number of legs and the 
few ones that stand on three supports use a strong tail (in the plane of symmetry) for this 
purpose. Likewise they have an even number of organs for sight and hearing and, if they 
have a single mouth in the symmetry plane, it is because they have a single digestive tube. 
Yet the nostrils are two, but this seems to be completely arbitrary. 


On our planet evolution developed also several living beings with radial symmetry of 
various order, like starfish (mostly of order five) or octopuses (order eight), hut none of 
them has articulated limbs or adapted to live on land; the mainstream of evolution leading 
to intelligence took a different path. 

The presence of a symmetry plane has some peculiar dynamic characteristics for a 
moving object (Genta, 2003) and robots with radial symmetry (mostly of order six) did not 
show particular advantages as walking machines (Genta and Amati, 2002), but this does not 
seem to rule out the possibility that in other biospheres intelligence may develop in animals 
with completely different symmetry characteristics. 

No douht that we can imagine (although with difficulty) ETIs with no symmetry at 
all. Radial symmetry is another possible choice, but other symmetries, much less familiar 
to us, are possible. In the mineral world, crystals exhibit many possibilities in this field; 
perhaps astrobiology will supply other examples. The fact that we cannot imagine them is 
immaterial: following Galileo it is what we should expect from extraterrestrials. 

4. Conclusions 

The humanoid layout has been shown to be an optimized response to the needs of an 
intelligent being living on the surface of a rocky planet, and our intelligence and our body 
evolved together and are closely matched. In spite of all this the belief that the humanoid 
layout is common among ETIs is quite naive. Evolution proceeds at random through small 
changes and cannot explore all the space of the configurations to search the optimal one 
to fill any ecological niche. It reaches near-optimum solutions which may be close to each 
other (convergent evolution) only if the genes producing them are potentially present in 
common ancestors. 

Much then depends on the way life started. If the supporters of panspermia are right 
(and the author thinks it is unlikely), and all living beings derive from some sort of organised 
matter containing genetic instructions, similarities can be larger and still larger will be if 
what is carried trough space are directly viruses or spores. Finally there is the problem of 
symmetry. On our planet the common origin didn’t prevent to experiment with different 
symmetries. The humanoid form might at best be the optimal solution for an intelligent 
being with bilateral symmetry, while different shapes can have been reached in places 
where different symmetries prevail. 

5. References 

Azuma, A. (1989), The Biokinetics of Flying and Swimming, Springer, Tokyo. 

Basalla, G. (1989), The Evolution of Technology, Cambridge University Press. 

Cavagna, G. A., Willems, P.A. and Heglund, N.C. (1998), Walking on Mars, Nature, Vol. 393, June, p. 636. 
Cockell, C.S. and Lee, M. (2002), Interstellar Predation, JBIS, Vol. 55, pp. 8-20, 2002. 

Coffey, E. J. ( 1 985), The Improbability of Behavioural Convergence in Aliens — Behavioural Implications of Mor- 
phology, JBIS, Vol. 38, pp. 515-520. 

Endler, J.A. (1993), Interactions between Predator and Prey, In: J.R. Krebs and N.B. Davies (eds.) Behavioural 
Ecology: an Evolutionary Approach., Scientihc Publications, Oxford, pp. 169-196. 

Galilei, G. (1613), Istoria e dimostrazioni intorno alle macchie solari e loro accidenti, Rome. 

Genta, G. (2003), Motor Vehicle Dynamics, World Scientihc, Singapore. 


Genta, G. and Amati, N. (2002), Non-Zoomorphic versus Zoomorphic Walking Machines and Robots: a Discus- 
sion, European Journal ofMech. & Env. Engineering, Vol. 47, n. 4, 2002, pp. 223—237. 

Leakey R. (2000), The Origin of Humankind, Orion Books Ltd., London. 

Minetti, A.E. (2001), Invariant Aspects of Human Locomotion in Different Gravitational Environments, Acta 
Astronautica, Vol. 39, No 3-10, pp. 191-198, 2001. 

Pickover, C. (1999), The Science of Aliens, Basic Books, Boulder, Colorado. 

Righetto, E. (2000), La scimmia aggiunta, Paravia, Torino. 

XII. The Search for Evolution of Intelligent 
Behavior and Density of Life 



U. S. Naval Observatory, 3450 Massachusetts Avenue, NW 
Washington, DC 20392-5420 USA. 

Abstract. Cosmic evolution embraces at least three vastly different possibilities for the destiny 
of life in the universe. The ultimate product of cosmic evolution may be only planets, stars and 
galaxies — a “physical universe” in which life is extremely rare. By contrast cosmic evolution, 
through biological evolution, may commonly result in life, mind and intelligence, an outcome 
that I term the “biological universe.” Taking a long-term view not often discussed, cultural 
evolution may have already produced artificial intelligence, constituting a “postbiological uni- 
verse.” Astronomical, biological and cultural evolution are the three components of the Drake 
Equation, and each component must he taken seriously. Each of the three possible outcomes of 
cosmic evolution results in a different destiny for life. But the destiny of life is not predictable; 
where intelligence is involved, the philosophical problem of free will must also play a role. 

I. Cosmic Evolution: Three Possible Outcomes 

Before discussing the destiny of life in the new universe, we must clarify what we mean 
hy “the new universe”. A century ago, most astronomers argued that the universe was only 
3,600 light years in extent, that the solar system was nearly at its center, and that humans 
were its ultimate purpose. The destiny of life was the destiny of humans, and that destiny 
was tied to religious and philosophical beliefs. 

Our view of the universe today has immensely enlarged. We now know that the visible 
horizon of our universe is about 13.7 billion light years in extent, and full of galaxies. We 
now know about the expanding universe, the accelerating universe, Einsteinian space-time, 
inflationary cosmology, and dark energy. But no concept has been so radical as cosmic 
evolution. The universe a century ago was static. Ours today is evolving, and cosmic evo- 
lution is the guiding principle for all of astronomy. Thus, in contrast to a century ago, we 
can speculate on the destiny of life — on Earth and in the universe - based on what we now 
know about cosmic evolution. 

The intellectual basis for this guiding principle of cosmic evolution had its roots in the 
19* century when a combination of Laplace’s nebular hypothesis and Darwinian evolution 
gave rise to the first tentative expressions of parts of this worldview. But cosmic biological 
evolution first had the potential to become a research program in the 1950s and 1960s when 
its cognitive elements had developed enough to become experimental and observational 
sciences. Harvard College Observatory Director Harlow Shapley was an early modern 


J. Seckbach et al. (eds.), Life in the Universe, 319 - 326 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


proponent of this concept, and already in 1958 spoke of it in now familiar terms, elaborating 
his belief in billions of planetary systems, where “life will emerge, persist and evolve” 
(Shapley, 1958). 

Already as the Space Age began, the concept of cosmic evolution - the connected 
evolution of planets, stars, galaxies and life - provided the grand context within which 
the enterprise of exobiology was undertaken. The idea of cosmic evolution spread rapidly 
over the next 40 years, both as a guiding principle within the scientific community and as 
an image familiar to the general public. NASA enthusiastically embraced, elaborated and 
spread the concept of cosmic evolution from the Big Bang to intelligence as part of its SETI 
and exobiology programs in the 1970s and 1980s. When in 1997 NASA published its Origins 
program Roadmap, it described the goal of the program as “following the 15 billion year 
long chain of events from the birth of the universe at the Big Bang, through the formation of 
chemical elements, galaxies, stars, and planets, through the mixing of chemicals and energy 
that cradles life on Earth, to the earliest self-replicating organisms — and the profusion of 
life”. With this proclamation of a new Origins program, cosmic evolution became the 
organizing principle for most of NASA’s space science effort. 

Today, the Big Question remains — how far does cosmic evolution commonly go? Does 
it end with the evolution of matter, or the evolution of life and intelligence? In this sense 
two astronomical worldviews hang in the balance in modern astronomy, just as they did 
four centuries ago when Galileo wrote his Dialogue on the Two Chief World Systems, and 
marshaled all the arguments for and against the geocentric and heliocentric theories. The 
two chief world systems today, I argue, are the physical universe, in which cosmic evolution 
commonly ends in planets, stars and galaxies, and the biological universe, in which cosmic 
evolution routinely results in life, mind and intelligence. We are on the brink today of 
being able to decide between these two worldviews. And that is why astrobiology is so 
important — it is the science that will decide which of these worldviews is true. I also argue 
that there may be a third worldview opened up by cosmic evolution — the postbiological 
universe based on cultural evolution. But it is not a worldview yet commonly discussed. 

2. The Physical Universe 

Almost all of the history of astronomy, from Stonehenge through much of the 20* cen- 
tury, deals with the people, the concepts, the techniques that gave rise to our knowledge of 
the physical universe. Babylonian and Greek models of planetary motion, medieval com- 
mentaries on Aristotle and Plato, the astonishing advances of Galileo, Kepler, Newton and 
their comrades in the Scientific Revolution, the details of planetary, stellar and galactic 
evolution — all these and more address the physical universe. The physical universe now 
boasts a whole bestiary of objects unknown a century ago — from blazars and quasars to 
pulsars and black holes. The quest for a biological universe should in no way obscure the 
fact that the physical universe is in itself truly amazing. 

Eor millennia the destiny of life in the universe was synonymous with the destiny of 
life on Earth, and was tied to the geocentric system associated with Aristotle, the Earth at 
the center and the heavens above. This cosmological worldview provided the very reference 
frame for daily life, religious and intellectual. The heliocentric system changed that, thus the 
societal uproar following this daring new cosmological worldview. Since then the history of 


modern astronomy has been one of increasing decentralization of humanity. Even though 
we are no longer physically central, the destiny of life in a physical universe in which life 
is very rare remains closely tied to humanity’s destiny. Ward and Brownlee (2003) have 
set forth the scenario of how Earth will eventually become uninhabitable. Long before that 
time, space travel will have taken us beyond the Earth, and of necessity it will have to take 
us beyond the solar system if we are to survive the death of the Sun. Then, the destiny of 
life is limited by the physical laws of the universe. As Chaisson (2001) has emphasized, 
we are now in the life era, but we will not always be. Adams and Laughlin (1999, 47-50) 
have laid out the fate of life on Earth in a cosmic context: in two billion years the Sun will 
have increased in brightness enough to induce a runaway greenhouse effect on our home 
planet. If we can escape to another star, however, our longevity rises considerably: the gas 
depletion rate indicates that star formation in galaxies will not halt for another 100 trillion 

Long before we have to face the challenges of Earth’s future, much less of the future 
of the universe, cultural evolution will have changed homo sapiens in fundamental ways. 
Indeed, some believe that cultural evolution will most likely have resulted in artificial 
intelligence within a few thousand years, and in the replacement of the species. Moravec 
(1988) and Kurzweil (1999) among others foresee this happening within a few hundred 
years. In science fiction terms, this physical universe, in which life and mind are rare but in 
which artificial intelligence is common, is fhe universe of Isaac Asimov’s Eoundafion series 
in science fiction. No non-human biological life is found in Asimov’s entire Eoundation 
series; the galaxy is populated by humans and by intelligent robots intimately associated 
with humans. There are no independent extraterrestrials. What may happen on Earth in the 
next few thousand years may have already happened among extraterrestrials. I will return 
to this idea of a postbiological universe later. 

If life is to be played out in this physical universe, the destiny of life is for humans, or 
their robotic ancestors, to populate the universe. In such a universe, where we are unique 
or very rare, stewardship of our pale blue dot takes on special significance. 

3. The Biological Universe 

The second possible outcome of cosmic evolution is the biological universe — the universe 
in which cosmic evolution commonly ends in life. Ideas about a possible biological universe 
date back to ancient Greece, in a history that is now well known (Dick, 1982; Crowe, 1986; 
Guthke, 1990; Dick, 1996). The Copernican revolution, which made the Earth a planet and 
the planets potential Earths, provided the theoretical underpinnings for extraterrestrial life. 
Much of the history of exobiology is an elaboration of this theme, attempting to show just 
how similar to the Earth the other planets really are. The idea of planets beyond the solar 
system also has a deep history stretching back at least to the 17* century with the vortex 
cosmology of Rene Descartes and the explicit depiction of planetary systems with Bernard 
le Bovier de Eontenelle’s Entretriens sur la pluralite des mondes (1686). Theoretical ideas 
about the formation of planets, and empirical searches for them, are an elaboration of this 

Over the last 40 years science has probed in a substantial way this new worldview 
of the biological universe. In the 1950s and 1960s four cognitive elements — planetary 


science, the search for planetary systems, origin of life studies, and SETI — converged to 
give birth to the field of exobiology (Dick, 1996). After the Viking missions failure to 
find life on Mars, in fhe 1990s many events conspired to revitalize exobiology: the Mars 
rock, the Mars Global Surveyor observations of the gullies of Mars, the Mars Odyssey 
detection of water near the surface, the Galileo observations of Europa, circumstellar matter, 
extrasolar planets, life in extreme environments including hydrothermal vents, and complex 
interstellar organics. All these elements fed into NASA’s new astrobiology program, which 
emerged from a deep organizational restructuring at NASA in 1995. Astrobiology now 
is a much more robust science than exobiology was 40 years ago. Astrobiology places 
life in the context of its planetary history, encompassing the search for planetary systems, 
the study of biosignatures, and the past, present and future of life. Astrobiology science 
added new techniques and concepts to exobiology’s repertoire, raised multidisciplinary 
work to a new level, and was motivated by new and tantalizing evidence for life beyond 

Astrobiology ’s image of a biological universe raises deep questions of the destiny of life 
and societal impact at many levels. When addressing societal impact, one must distinguish 
between a biological universe full of microbial life, and one full of intelligent life. Certainly 
the implications would be different. One is tempted to say that the impact of the discovery 
of microbial life would be limited to science, as biologists contemplated their first data 
for a universal theory of biology. But the reaction in 1996 when possible nanofossils were 
announced in the Mars rock clearly shows that the impact will be greater than that. 

The idea of intelligent life in the universe has already generated a long history of dis- 
cussion of potential impact, especially in the theological arena. In the Christian tradition, 
for example, discussion of the implications of extraterrestrial life for the doctrines of Re- 
demption and Incarnation now have a 500 year history (Crowe, 1986; Dick 2000b). More 
recently, NASA itself has sponsored a number of societal impact studies, in accordance 
with the National Aeronautics and Space Act goal of identifying the impact of the space 
program on society. In conjunction with the launching of the NASA SETI program, in 
1991-1992 NASA sponsored a systematic series of workshops on the cultural aspects of 
SETI (Billingham et al., 1999). And shortly after the astrobiology endeavor was launched, 
another group gathered to discuss broader concerns (Dick, 2000a; Harrison and Connell, 
1999). Although the cultural impact of discovering primitive life continues to receive little 
attention, the impact of contact with intelligent life has been the subject of much specula- 
tion, and some serious study. One approach is that historical analogs form a useful basis for 
discussion, not in the form of the usually disastrous physical cultural contacts on Earth, but 
by studying the transmission of knowledge across cultures and the reception of scientific 
worldviews (Dick, 1995). The Eoundation for the Future, which focuses on the question 
of the state of humanity a thousand years hence, sponsored a meeting on the implications 
of deciphering a message with high information content (Tough, 2000). And earlier this 
year the American Association for the Advancement of Science Program on the Dialogue 
between Science and Religion launched a series of workshops on the societal implications 
of astrobiology. Thus the societal impact of extraterrestrial life has been recognized from a 
variety of viewpoints, but much remains to be done. 

From another angle both scientists and historians of science have seen the idea of 
a universe full of life as a kind of worldview similar in status to the Copernican and 
Darwinian worldviews. Whether seen as a worldview, as one of the landmark questions of 


human thought, or as an essential element in the question of humanity’s place in nature, 
astrobiology has the potential to impact society no less than the other great revolutions of 
science. Indeed, one can see the UFO debate and alien theme in science fiction as attempts 
of popular culture to work out the new worldview. 

The destiny of human life in a biological universe is quite different from that in a 
physical universe. Rather than populating a universe empty of life, the destiny of humanity 
is perhaps to interact with extraterrestrials, to join what has been called a “galactic club” 
whose goal is to enhance knowledge. 

4. The Postbiological Universe 

In the remainder of this paper I want to argue that there is another option aside from the 
physical and the biological universe, an option that thus far has not been taken seriously. 
But if we take seriously physical and biological cosmic evolution, we also need to take 
seriously cultural evolution as an integral part of cosmic evolution and the Drake Equation. 
For those of you familiar with the vast sweep of time in Olaf Stapledon’s Last and First Men, 
you will know what I mean when I say that we need to think in Stapledonian terms. While 
astronomers are accustomed to thinking on cosmic time scales for physical processes, 
they are not accustomed to thinking on cosmic time scales for biology and culture. But 
cultural evolution now completely dominates biological evolution on Earth. Given the age 
of universe, and if intelligence is common, it may have evolved far beyond us. I have 
recently argued (Dick, 2003) that cultural evolution over thousands, millions or billions of 
years will likely result in a “postbiological universe” populated by artificial intelligence, with 
sweeping implications for SETI strategies and for our worldview. It also has implications 
for the destiny of life, indeed, artificial intelligence may be the destiny of life on Earth if it 
has already happened throughout the universe. We may see our future in the evolution of 
extraterrestrial civilizations. This is another motivation for searching. 

The three scientific premises for a postbiological universe are 1) that the maximum age 
of ETI is several billion years; 2) L, the lifetime of a technological civilization is >100 
years and probably much larger; and 3) in the long term cultural evolution will supersede 
biological evolution, and produced something far beyond biological intelligence. 

It is widely agreed that the maximum age of ETI, if it exists, is billions of years. Recent 
results from the WMAP place the age of the universe at 13.7 billion years, with a 1% 
uncertainty, and confirm that the first stars formed at about 200 million years after the Big 
Bang. The oldest Sun-like stars probably formed within about a billion years, or 12.5 billion 
years ago. By that time enough heavy element generation and interstellar seeding had taken 
place for the first rocky planets to form. Then, if Earth’s history is any guide, it may have 
taken another 5 billion years for intelligence to evolve. In a universe 13.7 billion years old, 
this means that the first intelligence could have evolved 7.5 billion years ago. Livio (1999) 
and Kardashev (1997), among others, have argued that extraterrestrial civilizations could 
be billions of years old, and it is commonly accepted among SETI practitioners. 

L, the lifetime of a technological civilization, is notoriously uncertain. Even pessimists 
admit 10,000 years is not unlikely. But the key point is that the age of ETI does not have to be 
large for cultural evolution to do its work. Even at our low current value of L on Earth, bio- 
logical evolution by natural selection is already being overtaken by cultural evolution, which 


is proceeding at a vastly faster pace than biological evolution (Dennett, 1996). Technologi- 
cal civilizations do not remain static; even the most conservative technological civilizations 
on Earth have not done so, and could not given the dynamics of technology and society. 
Unlike biological evolution, L need only be thousands of years for cultural evolution to 
have drastic effects on civilization. 

The course of cultural evolution is unpredictable even on Earth, much less in the universe. 
Darwinian models of cultural evolution have been the subject of much recent study (Lalande 
& Brown, 2000), but they are fraught with problems and controversy, whether drawn from 
sociobiology, behavioral ecology, evolutionary psychology, gene-culture co-evolution or 

While theoretical and empirical studies of cultural evolution hold hope for a science of 
cultural evolution, lacking a robust theory to at least guide our way, we are reduced at present 
to the extrapolation of current trends supplemented by only the most general evolutionary 
concepts. Several fields are most relevant, including genetic engineering, biotechnology, 
nanotechnology, and space travel. But one field — artificial intelligence — may dominate all 
other developments in the sense that other fields can be seen as subservient to intelligence. 
Biotechnology is a step on the road to AI, nanotechnology will help construct efficient AI 
and fulfill its goals, and space travel will spread AI. Genetic engineering may eventually 
provide another pathway toward increased intelligence, but it is limited by the structure of 
the human brain. In sorting priorities, I adopt what I term the central principle of cultural 
evolution, which I refer to as the Intelligence Principle: the maintenance, improvement and 
perpetuation of knowledge and intelligence is the central driving force of cultural evolution, 
and that to the extent intelligence can be improved, it will be improved. The Intelligence 
Principle implies that, given the opportunity to increase intelligence (and thereby knowl- 
edge), whether through biotechnology, genetic engineering or AI, any society would do so, 
or fail to do so at its own peril. I have elsewhere attempted to justify this principle (Dick, 
2003), but the argument comes down to is this: culture may have many driving forces, but 
none can be so fundamental, or so strong, as intelligence itself. 

The field of AI is a striking example of the Intelligence Principle of cultural evolution. 
Although there is much controversy over whether artificial intelligence can be constructed 
that is equivalent or superior to human intelligence — the so-called Strong AI argument — 
several AI experts have come to the conclusion that AI will eventually supersede human 
intelligence on Earth. Moravec (1988) spoke of “a world in which the human race has 
been swept away by the tide of cultural change, usurped by its own artificial progeny.” 
Kurzweil (1999) also sees the takeover of biological intelligence by AI, not by hostility, 
but by willing humans who have their brains scanned uploaded to a computer, and live 
their lives as software running on machines. Tipler (1994), well known for his work on the 
anthropic principle and the Fermi paradox, concluded that machines may not take over, but 
will at least enhance our well-being. But the self-reproducing von Neumann machines that 
Tipler foresaw in his explanation of the Fermi paradox may well exist if his view of the 
Fermi paradox is wrong. 

Thus, it is possible that L need not be millions of years for a postbiological universe 
scenario. It is possible that such a universe would exist if L exceeds a few hundred or a 
few thousand years, where L is defined as the lifetime of a technological civilization that 
has entered the electronic computer age (which on Earth approximately coincides with the 
usual definition of L as a radio communicative civilization. 


The postbiological universe cannot mean a universe totally devoid of biological in- 
telligence, since we are an obvious counterexample. Nor does it mean a universe devoid 
of lower life forms. Rather, the postbiological universe is one in which the majority of 
intelligent life has evolved beyond flesh and blood. The argument makes no more, and 
no fewer, assumptions about the probability of the evolution of intelligence or its abun- 
dance than standard SETI scenarios; it argues only that if such intelligence does arise, 
cultural evolution must be taken into account, and that this may result in a postbiological 

Thus it is possible that the destiny of life on Earth is artificial intelligence, and that other 
civilizations in the universe have already realized this destiny. How such postbiologicals — 
whether terrestrial or extraterrestrial — would use their knowledge and intelligence is a value 
question that is at present unanswerable. The likelihood of a postbiological universe and its 
implications should be systematically considered. Whether one relishes or opposes the idea 
of a universe dominated by machines, the transition to such a universe presents many moral 
dilemmas and raises with renewed urgency the ancient philosophical question of destiny 
and free will. 

5. Summary 

The new universe, driven by the astronomical, biological and cultural components of cosmic 
evolution, may result in any of the three outcomes described here: the physical universe, 
the biological universe, or the postbiological universe. Which of the three the universe has 
produced in reality we do not yet know — this is the challenge of astrobiology. But the 
outcome depends largely on what Davies (1998) has called the biofriendly universe. The 
question of the biofriendly universe brings us full circle to the physical universe with which 
we began, for the anthropic principle (more accurately termed the biocentric principle) 
postulates that a universe full of life is written into the very fabric of the physical universe, 
into its constants, laws and atomic structure. Our particular universe — the object of our 
contemplation and study over thousands of years — may indeed be a product of a highly 
evolved intelligence, albeit a natural intelligence. This brings us into the realm of theology, 
but not the usual supernatural and anthropocentric theology. It brings us to a cosmotheology 
(Dick, 2000), in which we need not enter the realm of the supernatural, any more than we 
require the fundamental Aristotelian dichotomy between the Earth and the Heavens that 
held sway for two millennia. It is a cosmos in which humanity is not central, yet where it is 
at home in the universe in which it plays its role. Whatever its long-term destiny, it is surely 
the destiny of humanity in the near future to follow the trail of scientific evidence wherever 
it may lead, even if it means abandoning old scientific, philosophical and theological ideas. 


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(ed.) Progress in the Search for Extraterrestrial LifePASP, San Francisco, 521-532. 

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Is it just a question of time? 


The Abdus Salam International Centre for Theoretical Physics. Strada 
Costiera 11; 34136 Trieste, Italy and Institute de Estudios Avanzados, 
Caracas 101 5 A, Venezuela. 

Abstract. Several issues have been raised regarding the nature of biology in a universal context: 
(1) life is a cosmic imperative (De Duve, 1995); (2) multicellular life is a rare phenomenon in the 
cosmos, although the existence of microbial life may still be widespread. This possibility has 
been referred as the “Rare-Earth” Hypothesis. (Ward and Brownlee, 2000). We shall develop a 
third possibility: (3) evolution of intelligent behavior is just a matter of time and preservation 
of steady planetary conditions, and hence ubiquitous in the universe (Chela-Flores, 2003a, b). 
Darwin’s theory of evolution is assumed to be the only theory that can adequately account for 
the phenomena that we associate with life anywhere in the universe. This question is motivated 
by the problem of understanding the bases on which we can get signiheant insights into the 
question of the distribution of life in the universe. Such information would also have deep 
implications on the other frontier of astrobiology mentioned above, the destiny of life in the 
universe. We argue in favor of the inevitability of life by assuming that Darwinian evolution is a 
universal process (Dawkins, 1983) and that the role of contingency has to be seen in the context 
of evolutionary convergence, not only in biology, but also in other realms of science. We shall 
restrict our discussions to astrobiology. The four areas which dehne this new science are: the 
origin, evolution, distribution and destiny of life in the universe. It is undoubtedly the fourth 
one, which is most likely to encourage interdisciplinary dialogue (Aretxaga, 2004; Vicuna and 
Serani-Merlo, 2004). 

1. Introduction 

We approach the empirical question of how to test the earliest stages of biological evolution 
in our own solar system, including Europa. For this purpose we may benefit from the results 
of the Galileo Mission to the Jovian system: Some of the Galileo results suggest that Europa 
has an inner core, a rocky mantle and a surface layer, mainly of liquid water. Impact craters 
also suggest that there is an ice-covered inner ocean, since they are shallower than would 
be expected on a solid (silicate) surface, such as that of the Moon. In the past we have 
considered a robot especially built to penetrate ice overlying a mass of liquid — the so- 
called ‘cryobot’ (Horvath et al., 1997). Others, more recently, are approaching the question 
of melting probes (Biele et al., 2002). A somewhat more remote possibility is to build a 
corresponding submersible robot (‘hydrobot’) capable of bearing some experiments in its 


J. Seckbach et al. (eds.), Life in the Universe, 327 - 331 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Are there Other Environments in the Cosmos that are Favorable to Life’s Origin? 

In the Europa Ocean, or possibly on the iced surface itself, we are presented with the 
problem of deciding whether biology experiments should be planned in due course (Gatta 
and Chela-Flores, 2004), and which tests should be taken to the stage of feasibility studies. 
We discuss some possible biosignatures of biochemical nature (Bhattacherjee and Chela- 
Flores, 2004) and comment on their relevance in the search for evolutionary biosignatures. 
In the original theory of Darwin the possibility had been raised that local environments 
shape how organisms change with time through natural selection. In view of the evidence 
discussed earlier (Chela-Flores, 2003a), we assume that natural selection is the main driving 
force of evolution in the universe. For these reasons it is relevant to question whether local 
environments that were favorable for the emergence of life on the early Earth, were at all 
unique, occurring exclusively in our own solar system. Alternatively, we may question, 
as we do in the present paper, whether other environments fulfill conditions favorable to 
life’s origin, either within our solar system, or in any of the planets, or satellites, in the 
multiple examples of solar systems known at present. In addition, we suppose that on such 
bodies steady conditions are preserved. By steady conditions it should be understood that 
the planet where life may evolve is bound to a star that lasts long enough: in other words, 
the time available for the origin and evolution of life should be sufficient to allow life itself 
to evolve before the solar system of the host planet, or satellite, reaches the final stages of 
stellar evolution, such as the red-giant and supernova phases. It is also assumed that major 
collisions of large meteorites with the world supporting life are infrequent after the solar 
system has passed through its early period of formation. 

3. Evolutionary Convergence at the Cosmic Level 

Cosmic evolutionary convergence may have some evidence at various levels, comets, me- 
teorites and high red shift data. Firstly, hydrogen and helium make up almost the totality 
of the chemical species of the Universe. Only 2% of matter is of a different nature, of 
which approximately one half is made by the five additional biogenic elements (C, N, O, 
S, P). We know that nuclear synthesis is relevant for the generation of the elements of the 
Periodic Table beyond hydrogen and helium and, eventually, for the first appearance of 
life in solar systems. The elements synthesized in stellar interiors are needed for making 
the organic compounds that have been observed in the circumstellar, as well as in inter- 
stellar medium, in comets, and other small bodies. The same biogenic elements are also 
needed for the synthesis of biomolecules of life. Besides, the spontaneous generation of 
amino acids in the interstellar medium is suggested by general arguments based on bio- 
chemistry: the detection of amino acids in the room-temperature residue of an interstellar 
ice analogue that was ultraviolet-irradiated in a high vacuum has yielded 16 amino acids, 
some of which are also found in meteorites (Munoz Caro et ai, 2002). There are factors, 
which contribute to the formation of habitable planets. Secondly, the Murchison meteorite 
may even play a role in the origin of life: According to chemical analyses, some amino 
acids have been found in several meteorites: in Murchison we find basic molecules for 
the origin of life such as lipids, nucleotides, and over 70 amino acids (Cronin and Chang, 


1993) . Most of the amino acids are not relevant to life on Earth and may be unique to mete- 
orites. This remark demonstrates that those amino acids present in the meteorite, which also 
play the role of protein monomers, are indeed of extraterrestrial origin.). If the presence of 
biomolecules on the early Earth is due in part to the bombardment of interplanetary dust par- 
ticles, or comets and meteorites, then the same phenomenon could have taken place in any 
of other solar systems. We shall not consider convergence at the molecular level (Doolittle, 

1994) , since it will be discussed separately in this volume (Akindahunsi, and Chela-Elores, 

4. On the Inevitability of Biological Evolution 

There is some evidence that once life originates provided sufficient (geologic) time is 
available, evolution is going to provide pressures to living organisms in every conceivable 
environment. This remark further advocates in favor of the hypothesis that once life appears 
at a microscopic level in a given planet or satellite, the eventual evolution of intelligent 
behavior is just a matter of time. 

Cambrian fauna, such as lamp shells (inarticulate brachiopods) and primitive mollusks 
(Monoplacophora), were maintained during Silurian times by microorganisms that lived in 
hydrothermal vents (Little et al, 1997). Taxonomic analysis of Cenozoic fossils suggests 
that shelly vent taxa are not ancestors of modem vent mollusks or brachiopods. We may 
conclude that modern vent taxa support the hypothesis that the vent environment is not a 
refuge for evolution. In fact, there is evidence that since the Paleozoic (e.g., the Silurian) 
and through the Mesozoic there has been movement of taxonomic groups in and out of 
the vent ecosystem through time — no single taxon has been unable to escape evolution- 
ary pressures. Some independent support for the thesis of deep-water extinction has also 
been presented (Jacobs and Lindberg, 1998). Hence, these remarks rale out the possibil- 
ity that these deep-sea environments are refuges against evolutionary pressures. In other 
words, the evidence so far does not support the idea that there might be environments, 
where ecosystems might escape biological evolution, not even at the very bottom of deep 
oceans. These remarks give some support to the hypothesis that any microorganism, in 
whatever environment on Earth, or elsewhere, would be inexorably subject to evolution- 
ary pressures. As we have shown above, fossils from Silurian hydrothermal-vent fauna 
demonstrate that there has been extinction of species on these locations, which at first sight 
seem to be far removed from evolutionary forces. For these reasons we may ask whether 
over geologic time the most primitive cellular blueprint has inevitably bloomed into full 
eukaryogenesis and beyond the evolutionary pathway to organisms displaying intelligent 

5. Discussion 

The arguments presented in this paper militate in favor of planning experiments based on 
standard biology in solar system search for microorganisms, in view of both evolutionary 
convergence and universal Darwinism. Ever since the publication of The origin of species. 


it has been argued that the possible course of evolution may be dominated by either con- 
tingency or the gradual action of natural selection. Random gene changes accumulating 
over time may imply that the course of evolution is generally unpredictable over time. But 
some care is needed in this assertion: What is certainly unpredictable is the future of a 
given lineage. This is due to the strong role in shaping life’s evolutionary pathways played 
by contingent factors, such as extinction of species due to asteroid collisions with a given 
inhabited world, or other calamities. 

However, the main issue is the inevitability of the appearance of biological features, 
such as vision, locomotion, nervous systems, brains and, consequently intelligent behavior. 
We have argued that contingency does not contradict a certain degree of predictability of 
the eventual biological properties that are likely to evolve. We should underline “biological 
property”, as opposed to a “lineage”, which is clearly a strongly dependent on contingency. 
However, from what we have explained above, such limited predictability is nevertheless 
relevant to aspects of the question of life in the solar system, as well as evolution of intelligent 
behavior in the universe. We have argued that fossils of hydrothermal vent fauna militate in 
favor of the possibility that once life appears at a microscopic level, the eventual evolution 
of intelligent behavior is just a matter of the environment surviving over geologic time. 
Possible tests of evolutionary biomarkers with the techniques of molecular biology were 

6. References 

Akindahunsi, A. A. and Chela-Flores, J. (2004) On the question of convergent evolution in biochemistry, in this 

Aretxaga, R. (2004) Astrobiology and Biocentrism, in this volume. 

Bhattacherjee, A. B and Chela-Flores, J. (2004) Search for bacterial waste as a possible signature of life on Europa, 
in this volume. 

Biele, J., Ulamec, J.S., Garry, Sheridan, S., Morse, A.D., Barber, S., Wright, I. R Tug, H. and Mock, T. (2002) 
Melting probes at Lake Vostok and Europa, ESA SP 518, pp. 253—260. 

Chela-Flores, J. (2001) The New Science of Astrobiology From Genesis of the Living Cell to Evolution of Intelligent 
Behavior in the Universe. Kluwer Academic Publishers: Dordrecht, The Netherlands, p. 161. 

Chela-Flores, J. (2003a) Astrobiology’s Last Frontiers: The distribution and destiny of Life in the Universe. In: 
J. Seckbach (ed.) Origins: Genesis, Evolution and Diversity of Life, volume 6 of the COLE book. Kluwer 
Academic Publishers, Dordrecht, The Netherlands, pp. xx— yy. 

Chela-Flores, J. (2003b). Testing Evolutionary Convergence on Europa. International Journal of Astrobiology 
(Cambridge University Press), in press. 

Cronin, J. R. and Chang, S. (1993) Organic matter in meteorites: Molecular and isotopic analyses of the Murchison 
meteorite. In: J.M. Greenberg, C.X. Mendoza-Gomez, and V. Pirronello, (eds.) The chemistry of life’s origins. 
Dordrecht: Kluwer Academic Publishers, pp. 209-258. 

Dawkins, R. (1983) Universal Darwinism, In: D.S. Bendall (ed.) Evolution from molecules to men, London, 
Cambridge University Press, pp. 403^25. 

De Duve, C. (1995) Vital Dust. Life as a cosmic imperative. New York, Basic Books, A Division of Harper Collins 
Publishers, pp. 296-297. 

Doolittle, R.F. (1994) Convergent evolution: the need to be explicit. Trends Biochem. Sci. 19, pp. 15-18. 

Gatta, R. S. and Chela-Flores, J. (2004) Application of molecular biology techniques in astrobiology, in this 

Horvath, J., Carsey, F, Cutts, J. Jones, J. Johnson, E., Landry, B., Lane, L., Lynch, G., Chela-Flores, J., Jeng, T-W. 
and Bradley, A. (1997), 

Jacobs, D.K. and Lindberg, D.R. (1998) Oxygen and evolutionary patterns in the sea: Onshore/offshore trends 
and recent recruitment of deep-sea faunas, Proc. Natl. Acad. Sci. USA 95, pp. 9396—9401. 

Little, C.T.S., Herrington, R.J., Maslennikov, V.V., Morris, N.J. and Zaykov, V.V. (1997) Silurian hydrothermal- 
vent community from the southern Urals, Russia, Nature 385, pp. 146-148. 


Munoz Caro, G.M., Meierhenrich, U.J., Schutte, W.A., Barbier, B., Arcones Segovia, A., Rosenbauer, 
H., Thiemann, W.H.R, Brack, A., and Greenberg, J.M. (2002) Amino acids from ultraviolet irradiation of 
interstellar ice analogues, Nature 416, pp. 403—406. 

Vicuna, R. and Serani-Merlo, A. (2004) Chance or Design in the Origin of Living Beings An epistemological 
point of view, in this volume. 

Ward, RD. and Brownlee, D. (2000) Rare Earth: Why Complex Life is Uncommon in the Universe. Copernicus, 
New York. 


D.E.E.I., Universita di Trieste, Trieste, Italy 

1. Introduction 

This note summarizes our general line of research on the evolution of intelligence with 
a particular emphasis on human language and mathematics as innate cognitive faculties, 
capabilities, which set our species apart from non-human primates. At the psychological 
level of abstraction, human intelligence can be considered as a collection of interacting 
modules of such mental faculties as language, theory of Mind (ToM), meta-mind and 
others (Shah 1998). Modules at lower level can be considered as “pre-adaptations” in the 
evolutionary sense that these are required for the emergence of higher cognitive functions 
like inventing mathematics and generation and comprehension of language. We outline our 
“emergence-at-threshold” model of language in terms of other ‘simpler’ mental faculties 
such as ToM and unbounded generativity, namely FLN of Hauser-Chomsky-Fitch (2002). 
Using this model, we estimate that modern human language, FLB in Hauser-Chomsky-Fitch 
(HCF) sense, emerged around 40,000 years ago. 

Our effort to model language evolution was stimulated by HCF and the following two 
questions posed by Christiansen & Kirby (2003): 

1 . What are the necessary and sufficient pre-adaptations for language! 

2. Can genetic and archaeological evidence converge on a timetable for the origins 
of language in hominids! 

2 . The Model 

In the astrobiological context, a research program on the origins and evolution of intelligence 
as defined above requires a three-fold effort. First, evolutionary convergence in the broad 
sense (ECB) is to be investigated. This includes not only the re-emergence of terrestrial 
intelligence ‘if the tape is played again’ but also emergence of extraterrestrial intelligence 
(Shah 2001) elsewhere in the universe. A study of ECB should take into account adaptation, 
exaptation, task-directed evolution due to organism-environment interaction, and emergent 
higher cognitive modules as a consequence of threshold behaviour of a collection of inter- 
acting pre-adaptations, i.e., lower level cognitive modules. Second, an understanding of the 
nature and evolution of complex cognitive systems and their underlying nervous systems is 
necessary. Third, we need to clarify the nature of cognitive reality — reality as perceived by a 


J. Seckbach et al. (eds.), Life in the Universe, 333 - 334 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


cognitive system. The basic assumptions of this line of research are continuity of evolution, 
modularity (Fodor 1983) and domain-specificity (see, e.g., Hirshfeld & Gelman 1994). 

There seems to be consensus that some pre-adaptations became available to the hominid 
line prior to emergence of language (Christiansen & Kirby 2003). We should, therefore, 
take into account all such underlying pre-adaptations in order to explain the emergence of 
language. At present, this is debated as to what these may have been. This line of thinking 
conhrms our view point presented in Shah (1998) in the context of general intelligence. Our 
hypothesis is that these pre-adaptations reached a threshold and began to interact with each 
other only in hominid lineage, but not in non-human primates or in other species, but they 
are shared with many other species and seems qualitatively to be the same. An outline of 
necessary cognitive modules as pre-adaptation is given as follows (details are to be found 
in their respective references). 

Symbolic Representation (see, e.g., Fodor & Pylyshyn 1988): This capacity could be as 
old as 1.5 million years and it is highly probable that symbolic representation pre-dated all 
other cognitive modules given below. 

Recursive Generativity and Systematicity (Bloom 1994, Pylyshyn 1884) 

Meta-mind (Suddendorf 1999) 

Theory of Mind (Baron-Cohen 1999) 

Granularity (Shah 1998, see references therein) 

The other necessary modules are working memory, long-term memory and perceptual input 
interface (sensory modalities). We have not investigated the sufficiency issue in terms of 
pre-adaptations. The schizophrenia hypothesis of language origin considers left hemisphere 
dominance as the critical change dating it to 50,000 years (Crow 2000). The existence of 
meta-mind dates to around 50,000 years as well (Suddendorf 1999). However, theory of 
mind is suggested to be no more than 40,000 years old (Baron-Cohen 1999). Since ToM is 
essential to pragmatics of language, FLB, the full human language originated no more than 
40,000 years ago. 

3. References 

Baron-Cohen, S. (1999) The evolution of a theory of mind, In: M.C. Corballis and S.E.G. Lea {Qds.)The Decent 
of Mind, psychological perspectives on hominid evolution, , Oxford University Press, pp. 261-277. 

Bloom, P. (1994) Generativity within language and other cognitive domains, Cognition 51, 177-189. 

Christiansen, M.H. and Kirby, S. (2003) Language evolution, TRENDS in Cognitive Sciences 7, 300-307. 

Crow, Y.J. (2000) Schizophrenia as the price that Homo sapiens pays for language: a resolution of the central 
paradox in the origin of species. Brain Research Interactive 31, 118-129. 

Fodor, J.A. & Pylyshyn, Z.W. (1988) Connectionism and Cognitive Architecture, Cognition, 28, 3-71. 

Hauser, M.D., Chomsky, N. and Fitch, W.T. (2002) The Faculty of Language: What Is It, Who Has It, and How 
Did It Evolve? Science 298, 1569-1579. 

Hirshfeld, L.A., and Gelman, S. (eds.) (1994) Mapping the mind, Cambridge University Press, New York. 

Pylyshyn, Z. W. (1984) Computation and Cognition, The MIT Press, Cambridge (Mass), USA. 

Shah, K. T. (1998) Cognitive Universals: Abstract Psychology of Terrestrial and Extraterrestrial Intelligence, In: 
J. Chela-Flores and F. Raulin (eds.) Exobiology: Matter, Energy and Information in the Origin and Evolution 
of Life in the Universe, Kluwer Academic Press, pp. 161-164. 

Shah, K. T. (2001), Testing Evolutionary Convergence: From RNA World to Intelligence, In: J. Chela-Flores and 
F. Raulin (eds.) Eirst Steps in the Origin of Life in the Universe, Kluwer Academic Press, pp. 261-266. 

Suddendorf, T. (1999), The rise of meta-mind. In: M.C. Corballis and S.E.G. Lea (eds.) The Decent of Mind, 
psychological perspectives on hominid evolution, Oxford University Press, pp. 218-261. 



Pontifical University of the Holy Cross, 

P. Sant’Apollinare 49, 00186 Roma (RM)-Italy 

1. Age and Advancement 

According to a very widespread commonplace, if any extraterrestrial civilization does exist, 
it is very likely to be much more advanced than ours. Surely, it is likely to be even one billion 
years older (Norris, 2000). But does it implies that it would be also one billion years more 
advanced! In reality, this equivalence requires a further assumption, i.e. that technological 
progress is an endless process. But technological progress is based on scientific one. In fact, 
without substantial advancements in science, we can only improve the existing techniques 
until the full exploitation of their possibilities, established by the laws of nature they are 
based on. So, an endless technological progress implies that scientific progress is endless, 

2. The End of Science? The Morgan’s Challenge 

In 1996 appeared in the USA The end of science, by John Morgan (Morgan, 1996), radically 
challenging such a view. In fact, in his book Morgan maintained not only that science is not 
endless in principle, but that it is ending actually, so that we are already in the decreasing 
part of the curve. Morgan’s argument is very simple: science is aimed to discovery the 
fundamental laws of nature; of course, if it cannot succeed, it will have to stop somewhere 
before reaching them; but if it can succeed, then it will discovery all the laws and then it 
will have to stop. Thus, in any case science have to stop, soon or later. Then, he showed 
many historical examples, all seeming to support his theory. 

3. A Statistical Evaluation 

While in principle Morgan is surely right, the most challenging part of his theory is the second 
one, i.e. that science on Earth is ending just now. In fact, if science wouldn ’t be endless, but 
would take a billion years to end actually, the previous equivalence would still hold. So, a 
first (and very rough) attempt of a statistical evaluation of this crucial point is here provided, 
based on the data coming from a popular handbook (Rivieccio, 2001). Both discoveries and 
inventions seem to follow a typical bell curve, which is already in its decreasing half, even 
though the second is less sharply defined (fig. 1). Moreover, shifting the discovery curve 


J. Seckbach et al. (eds.), Life in the Universe, 335 - 337 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


■ Discoveries □ Inventions 

I World War Crisis 

^ ^ ^ ^ 

Figure 1. 

Figure 2. 

■ Discoveries □ Inventions 

towards the right of 25 years (just a generation, that is the time presumably needed to learn 
how to apply scientihc discoveries to technology) we see that their fitness becomes almost 
perfect, the only exception possibly being due to the big crisis which followed the First 
World War (fig. 2). 

4. Conclusions 

1 . Despite the increasing amount of new technological products, the number of sub- 
stantial technological novelties seems to be decreasing, and it is likely to be de- 
creasing at least in the next 25 years, too. If so, Morgan could be right. 

2. A possible inversion of this trend seems to strictly depend on a new deal of discover- 
ies in fundamental science, whose number, on the contrary, is regularly decreasing 
from about 1950. 

3. According to the present trend, the age of substantial technological innovations 
on Earth is likely to end in about two centuries. Notice that such a conclusion 
fits very well with the widespread opinion that, at least in a well defined field, 
i.e. radioastronomy, at present we have already reached the half of the maximum 
possible degree of efficiency (Oliver, 1971). If so, an extraterrestrial civilization 
one billion years older than ours might be only two centuries more advanced. 


4. Since we are still very far from reaching the capability for interstellar travels, and 
only two centuries more of (decreasing) progress may not be enough, this may be 
an impossible goal. If so, SETI could really be our only chance to get in touch with 
any possible extraterrestrial civilization. 

5. Further and more professional studies are needed to better clarify this issue. 

5. References 

Norris, R. (2000) How Old is ET?, In: A. Tough (ed.) (2000) When SETI Succeeds: The Impact of High-Information 
Contact, Foundation For the Future, Washington, pp. 103—105. 

Horgan, J. (1996) The End of Science, New York; trad. it. 1998, La fine della scienza, Adelphi, Milano. 
Rivieccio, G. (2001) Dizionario delle scoperte scientifiche e delle invenzioni, Rizzoli, Milano. 

Oliver, B.M. (1971, reprint 1996) Project Cyclops, SETI League & SETI Institute. 

XIII. Epistemological and Historical 
Aspects of Astrobiology 

An Epistemological Point of View 


* Facultad de Ciencias Bioldgicas, Pontificia Universidad Catolica de 
Chile. Casilla 114-D, Santiago, Chile, and Millenium Institute of 
Fundamental and Applied Biology; ^Facultad de Medicina, Universidad 
de los Andes. San Carlos de Apoquindo 2200, Santiago, Chile. 

1. The Rational Understanding of Living Beings 

The judgment that the natural world is composed by living and non-living entities is one 
of the most ancient and spontaneous intuitions of humankind. Natural science, which is the 
critical, systematic and methodical deepening of these first and firm intuitions, consequently 
divides itself into biology, with its wide cohort of disciplines, and physico-chemical sciences, 
encompassing the majority of divisions. 

The intellectual understanding and the formal conceptual expression of the uniqueness 
of living beings has challenged biologists and natural philosophers since the days of the 
Greek naturalists. Henceforth, the origin of living beings has been viewed as being tightly 
linked to the definition and explanation of the essence of life (Maturana et al, 1974). 

If living beings are no more than complex material devices, organized fortuitously by the 
free interaction of blind mechanical forces and whose survival depends on its fitness to 
the environment — as the ancient Greek atomists first sustained — , then the explanation of 
the origin of life must lie on strictly mechanical explanations. If, on the other hand, living 
beings are unique natural entities, fundamentally different from non-living beings — as Plato 
and Aristotle affirmed — , then the explanation of their origin must include other causes in 
addition to mechanical ones. These non-mechanical causes were not conceived by these 
philosophers as forces in the vitalist way, but as real aspects or levels of explanation in 
natural beings. 

In the ancient Greek non-creationist cosmological context, the explanation about the 
origin of life reverted to chance in the materialistic view, or to some kind of formal and 
final causality in the non-materialist view. In spite of the many nuances that have been 
introduced to the problem through the centuries, the basic opposing philosophical views 
seem to remain virtually untouched. Some authors, in the vein of Oparin and others, ad- 
hering explicitly to philosophically materialistic views, have sought grounding for their 
theoretical speculations in the experimental evidence provided by modern science. On the 
other hand — and also claiming to base their speculations in data provided by contemporary 
biological knowledge — an increasing number of authors try to substantiate that the origin 
and diversification of living beings would have been impossible without the recourse to 


J. Seckbach et al. (eds.), Life in the Universe, 341 - 344 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


other kinds of causes (non-reductionism), to the intervention of an intentional intelligent 
cause (intelligent design) or even to the direct intervention of God (creationism). 

Herein, we propose an epistemological clarification that could facilitate interdisciplinary 
discussions and open the way to conciliate opposing philosophical views by recognizing 
the fragments of truth contained within each stance. 

2. Epistemological Considerations 

Every scientific discipline, whatever the subject it covers, relates to facts and with the 
rational understanding of those facts (Maritain, 1983). As Maritain sustained, the notion of 
fact is analogical. Therefore, evidence in any science, including philosophy, mathematics, 
the natural sciences and the social sciences, must possess its own facts from where to proceed 
in its way of conceptualization and reasoning. In the realm of natural experimental sciences, 
facts are defined in a quite restrictive manner as those perceptible empirical phenomena 
related to the particular field of study (Simon, 1999). Even if empirical facts are entirely 
referred to sensible perception, they are formally expressed in judgements. 

Starting from this empirical phenomenology, a variety of possible objectives become 
possible. When a student of biology decides to devote himself to systematics, morphology, 
biochemistry, physiology or ethology, what he is in fact doing is choosing an option for a 
particular and restricted point of view. Every biologist working in subdisciplines of exper- 
imental biology accepts other disciplines as legitimate but distinct intellectual avenues to 
the understanding of living phenomena. 

Experimental biologists don’t need an explicit formal definition of living beings to carry 
out their work. However, it is plain, from an epistemological point of view, that for every 
biologist the affirmation of the existence of living beings as original and distinguishable 
entities in the physical world, is an absolute pre-requisite for the existence of its correspond- 
ing discipline. This constitutes a fact which every experimental scientist in any branch of 
biology has to take for granted (Meyerson, 1951). 

This also applies to the definition of living beings. It is implicitly obvious for every 
biologist that if living entities exist they must have a proper definition, whatever it could 
be. Erom a philosophical point of view, this is one of the first and most evident facts on 
which all human understanding lies: everything that exists is something and the adequate 
conceptual expression of this “somethingness” is what we call its definition. 

Although biologists do not need to formally define the distinct existence of living beings , 
two precisions must be made: 

1 . Even if biologists don’t need a formal definition of living beings in order to conduct 
their work, they absolutely require at least an implicit recognition of the original 
existence of their subject matter and a general or working definition of this same 
study subject. 

2. This kind of fundamental questioning does not leave scientists indifferent in regards 
to their reflective thinking and interpretation of experimental work. Moreover, it 
seems to be in the natural order of things that as an experimental biologist grows 
older, the more intrigued they become in relating the questions answered and 
proposed in their discipline to a unifying theory of scientific doctrine. 


What kind of questions are these, whose answers are in some manner presupposed by the 
natural sciences, but that cannot be answered formally within their own conceptual frame? 
On which grounds can these questions be adequately answered? In which manner scientific 
developments of the natural experimental sciences contribute to a better understanding of 
the distinct nature of living beings and of the causes of their origin? Are, in some way, the 
natural experimental sciences continuingly answering these fundamental questions in their 
own particular manner? 

We propose that the adequate definition of the uniqueness of living beings and the 
inevitable following questions, namely the how and why of the origin of this uniqueness, 
cannot be univocally answered. This definition must be approached in different but related 

Experimental biologists, who must in practice take for granted the existence and philo- 
sophical definition of living beings, have the task of defining living beings from a strictly 
experimental stance. Each time that biochemists, for example, describe the chemical com- 
position of a particular organism and elucidate the metabolic pathways that produce and 
maintain those entities, they are defining in very concrete terms a living organism from a 
biochemical viewpoint. The epistemological question, dealing with the existence of other 
possible views, either in the experimental or the theoretical realms, is not a matter that can 
be biochemically approached. In other words, a biochemist is unable to answer a question 
that cannot be rigorously defined in biochemical terms. 

3. Epistemological Proposal 

We propose that in discussions concerning the origin of life, at least three distinct episte- 
mologically arguments are applied within the same discussion. 

Eirst of all, experimental scientific questions are relevant for the discussion on the origin 
of life. Studies on the physico-chemical properties of water, the biochemical characteristics 
of ribozymes, or the genetic code of the mitochondria are some examples of these pertinent 
scientific matters that can be rightly approached on experimental terms. 

Secondly, there are questions whose answers are out of the reach of experimental demon- 
stration and that must be ultimately resolved in philosophical terms. Examples of these could 
be: Is the origin of living beings the result of the interaction of purely physicochemical forces 
that coincided by chance in some way under fortuitous circumstances? Or are living beings 
the result of an intentional design either immanent in natural processes or transcendent 
to the physical world? Is there any conceivable manner in which both answers could be 
legitimately combined? 

Einally, there are historical or paleontological questions that are out of the reach of 
actual experimentation: Did the first living beings emerge from a primordial soup or from a 
primitive solid substrate of clay? Did eukaryotes emerge from prokaryotes? What exactly 
happened in the pre-Cambrian to Cambrian transition? Such singular historical biological 
facts, which are not deducible from verified general natural laws and that occurred under 
non-reproducible conditions, cannot be directly studied by current scientific mefhods. Eor 
example, in invesfigafing fhe physical transformation that a subset of living beings under- 
went during Cambrian transition, we are confronting an historical fact that can only be 
approached by historical or paleontological speculation. 


A biochemist can speculate on philosophical or historical questions that are outside 
the strict realm of biochemistry and provide experimental evidence for this speculation. A 
biochemist is free to speculate about the origin of living beings in time and place, and on the 
mutations they have subsequently undergone. However, a classical biochemical approach 
cannot wholly answer philosophical or historical questions. Biochemistry cannot have bio- 
chemical answers to non-biochemical questions, even if they are posed in biochemical 

We advocate in this proposal that paleontological speculations, based on actual exper- 
imental data are not necessarily contradictory with philosophical reasoning. Indeed, what 
appears contradictory are the mechanistic versus non mechanistic philosophical statements. 
We propose, that even on philosophical grounds, chance and design are not necessarily con- 
tradictory. There are numerous examples in which human design considers or even relies 
on the role of chance. 

If correct in our affirmation, it would be legitimate for a biologist, -while thinking 
‘paleontologically’ — , to reason on empirical basis, while at the same time, thinking as a 
philosopher, reason on intentional design. Only when a biologist/biochemist also affirms 
as a philosopher the truth of an empirical view, a final/intentional design position can be 
regarded as contradictory to his statements. 

4. References 

Maritain, J. (1983) Les degrees du savoir, rf 18 Eclaircissements sur la notion de fait. Fribourg-Paris, Editions 
Universitaires de Fribourg Suisse/ Editions Saint Paul, pp. 361-365. 

Maturana H.R., Varela, F.R. and Uribe, R. (1974) Autopoiesis: The organization of the living, its characterization 
and a model. Bio Systems 5, pp. 187—196. 

Meyerson, (1951) E. Identite et Realite, Paris, pp. 327-384. 

Simon, I. (1999) Maritain’s Philosophy of the Sciences. In A. Simon Philosopher at work, Lanham/Maryland, 
Rowman & Littlefield Publishers Inc., pp. 21^0. 



Philosophy Department, School of Philosophy and Educational Sciences 
University ofDeusto, Bilbao, Spain 

1 . Philosophical and Environmental Biocentrism 

The term “biocentrism” is polysemic in as far as it has, at least, three different meanings. One 
of them is to be found in the held of Philosophy, another in the Environmental Sciences, and 
a third interpretation is also provided in the area of astrobiology. In the held of philosophy, 
the term “biocentrism” is used to describe that ethical theory which denies that human heings 
occupy a privileged position with respect to other living creatures, as well as humankind’s 
centrality as a source of universal values. Life at large is taken as the only source and holder 
of any value by biocentrism, which implies that humanity is displaced from its central 
position, and so biocentrism is anti-anthropocentric. This is the usage the term is given 
in the “deep ecology” and conservation movement, based on the theories developed by 
Aldo Leopold and Paul W. Taylor. The second use of “biocentrism” is opposed to that of 
“functionalism”. In this sense, these two designations refer to opposing views in the study 
and management of the environment, which, in turn, have generated two distinct scientihc 
disciplines: population ecology and system ecology, respectively. Bearing this difference 
in mind, biocentrism is best characterized as focusing on organisms and taking the “biota” 
as its basic component. Besides, biocentrism relies on natural selection as its explanatory 
paradigm and defends biodiversity. 

Lunctionalism, on the other hand, conceives both organisms and the abiotic component 
as a whole (holistically), that is, not just a mere addition of the parts. It has also made of the 
flowing of matter and energy its main object of analysis, and of the laws of thermodynamics 
its explanatory paradigm. Lunctionalism favors ecodiversity over biodiversity, and maintains 
that it is the preservation of the flowing of matter and energy typical of any ecosystem that 
guarantees the survival of its organisms. 

Before I move on to discuss the astrobiological sense of the term “biocentrism”, I will 
consider some of the implications that the above mentioned usage of the term: 

(a) The philosophical conception of the term “biocentrism” brings up a relevant is- 
sue for astrobiology; since this science assumes the existence of a common ancestor and 
the evolutionary theory, it would seem natural to align it with the biocentristic — anti- 
anthropocentric — position in the debate. However, under no circumstances could astro- 
biology ignore the fact that human culture represents a real peculiarity among the different 
forms of life and adaptation on our planet. If life is found on other planets, this fact would 
broaden the horizon of the philosophical debate started by ethical biocentrism, a horizon 


J. Seckbach et al. (eds.), Life in the Universe, 345 - 348 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


that could then be opened to hitherto unheard-of ideas and views. One possible solution to 
the underlying philosophical dilemma may come from the distinction between “strongly 
anthropocentric” and “weakly anthropocentric” (Norton, 1984) proposed by Bryan G. 

(b) We may assume that the environmental conception of the term “biocentrism” has 
implications for astrobiology, too. Thus, since it takes an interest in the origin and distribution 
of life, and it focuses on the study of microscopic life and its exchanges with the environment, 
astrobiology seems to require a functional approach. But as it is also concerned with the 
evolution and destiny of life, and especially with multi-cellular intelligent organisms, the 
biocentric approach would be the most adequate. 

The conflict between biocentrism and functionalism in the ecological sciences can be 
solved by emphasizing the complementary nature of both paradigms, and by arguing that 
the use of one or the other depends exclusively on the spatial and temporal parameters to be 
considered in each case. Thus, while the functional approach offers a better understanding 
in the study and management of large ecosystems with small organisms; the biocentric one, 
is rather more suitable for the analysis of ecosystems of a smaller size but with bigger organ- 
isms. With respect to astrobiology, its multi/inter-disciplinary character, and the diversity 
of its subject matter, also seem to encourage the integration of both approaches, depending 
on the spatial and temporal parameter that is necessary in each case. 

2. Astrobiological Biocentrism 

The phrase “astrobiological biocentrism” (AB) or “astrobiological conception of the term 
biocentrism” refers to biocentrism in the sense in which Chela-Flores understands it when 
he defines it as “the belief that life has occurred only on Earth” (Chela-Flores, 1998), or 
“the doctrine which defends the singularity of the biological evolution that has taken place 
on Earth, from a bacteria to human beings” (Chela-Elores, 2003). 

Chela-Elores’ definition of the term “biocentrism” is likely to generate a philosophically 
relevant question. As a “belief”, biocentrism does not constitute in itself a rationally-based 
and articulated system of ideas, but rather an inner conviction of an individual or a commu- 
nity which, admittedly or not, consciously or not, justifiably or not organizes and governs 
their thoughts and deeds. Erom this point of view, the term “biocentrism” may be analyzed 
in the light of Husserl’s “life’s world” (Lebenswelt) and Ortega y Gasset’s “belief” (creen- 
cid). As a “doctrine”, however, biocentrism is a theory — on the same footing as that built 
by J. Monod and others — which takes part in what T. S. Kuhn calls a “scientific paradigm”. 
In this sense, the term “biocentrism” would belong in the category that Ortega y Gasset 
refers to as “idea” (idea). However, in both cases biocentrism is one of the explanatory 
keys in our contemporary way of knowing, understanding, evaluating and explaining the 
universe, life and humankind. Consequently, biocentrism also becomes one of the main 
pillars of our contemporary “conception of the world” (Weltanschauung, Dilthey), and it is 
this aspect precisely that needs to be highlighted when talking about AB, which comprises 
both meanings — that of “belief” and that of “idea”. With all this in mind, I will now dwell 
upon the relation between AB and astrobiology as a science. 

The issue of the existence of extraterrestrial life and of the plurality of worlds was al- 
ready raised in ancient times (Dick, 1984), which means that astrobiology has its roots in an 


age-old human quest. In any case, as a contemporary science, astrobiology is indebted to 
20th-century theories, techniques and methods that have revolutionized the way in which 
human beings have access to and present “the real” — physical, or living. Moreover, astrobi- 
ology is likely to engage all the other disciplines of human knowledge in its investigations 
(Aretxaga, 2003). 

Copernicus and Galileo put an end to geocentrism. Darwin laid the foundations to 
leave behind anthropocentrism. In my opinion, what is really important about each of their 
scientihc contributions in astronomy and biology is that they caused a radical change in our 
conception of the universe, of man and of man’s role in this world, something that became 
apparent in profound cultural and sociological transformations. 

With regard to AB, it is still, as geocentrism and anthropocentrism were in their time, 
just one of the pillars of our civilization, since up to now there is no strong evidence for the 
existence of other life forms in different planets. But it is also well-known that the lack of 
any evidence of the existence of extraterrestrial life does not necessarily entail its absence. 
Astrobiological discoveries do not only support this hypothesis, but also begin to undermine 
the foundations of biocentrism as a scientific theory. As a result, such knowledge has historic 
relevance, since they constitute the basis to prove empirically the falsity of biocentrism. This 
fact allows us to nourish hopes that we are facing a future — and perhaps not a very remote 
one — of scientific contributions which, like Galileo’s or Darwin’s, will go down in history, 
not just on account of its scientific and technological significance, but above all due to its 
new and revolutionary consequences for all the other aspects that constitute the different 
human cultures and societies (for instance, philosophy, art, religion, politics and literature). 

In view of what has been said above, it seems reasonable to consider biocentrism 
as an obstacle for human progress (Chela-Flores, 2001) because, similar to geocentrism 
and anthropocentrism in their heyday, at present, biocentrism would seem a hindrance 
to mankind’s development of a more truthful image of itself and, therefore, to a finer 
understanding of its real place in the world, and of the new type of responsibilities that 
accompany this change. Furthermore, if as a general rule a reliable knowledge contributes 
to raising the levels of adaptability, learning the truth about biocentrism will ensure the 
survival of the human race. 

Taking the above arguments under consideration, the need to discover and analyze the 
role of biocentrism seems both inescapable and responsible, since it is one of the elements 
shaping the numerous and complex aspects that constitute human cultures and societies. 
This task leads to a better understanding of the character and depth of the changes and 
implications that the eventual decline of biocentrism would involve. This, in turn, makes it 
easier for the complementary task of investigating alternative models designed to approach 
future problems with more flexibility and effectiveness. In this context, and although it 
is not the business of humanists, but rather astrobiologists to demonstrate the falsity of 
biocentrism, philosophers and humanists do have to exercise and to encourage thought 
processes that help mankind as a whole to understand and take in the implications that the 
effects of an eventual success of astrobiology in its quest for life, present or past, outside 
planet earth. 

In this particular area, some invaluable contributions have been made by the SETI 
Institute concerning extraterrestrial intelligence (Billingham et al., 1994; Tough, 2000). 
Considering everything that has been stated so far, there is little doubt of the necessity to 
strengthen and promote cooperation between astrobiologists and humanists. 


3. Discussion and Conclusion 

The existence of three different conceptions of the term “biocentrism” has important im- 
plications for astrobiology. Thus, the philosophical and environmental conceptions have 
ethical and methodological consequences, respectively. In what concerns the conception, 
theories, methods and techniques of which astrobiology makes use can be said to offer us 
the historic opportunity of experimentally solving the question of whether we are alone or 
not in the universe or, the relation existing between our own evolution and that of other 
forms of life that may have developed somewhere else in the universe (Chela-Flores, 2001). 
The current state of the art suggests AB makes no reference to reality, but only represents 
an unjustified belief and a scientific theory based on partly out-dated knowledge. Thus, 
speaking of an incipient crisis of biocentrism brought about by the new astrobiological 
contributions does not seem hasty. Given the important role played by AB in the shaping of 
our culture and society, the possibility of its demise as a belief and as a theory would cause 
not only profound scientific changes, but also, and perhaps more importantly, cultural and 
social ones. 

Astrobiology then, far from being a field of specialization only open to scientists, should 
also hold great interest for humanists since this theory may compel humankind to readjust 
their own perceptions as a race and to question their place in the universe, which will even- 
tually contribute to their progress. This insight implies a responsible and efficient practice 
of reflection and investigation that requires, in turn, increasing cooperation between astro- 
biology and the humanities that should draw closer in order to make the aforesaid progress 
evident in all the dimensions that constitute the different human cultures and societies. 
To conclude, and in an attempt to avoid problems of terminology, I would recommend 
that the term “biogeocentrism”, which has already been employed by Chela-Flores himself 
occasionally, be used to refer to what I have called here “astrobiological biocentrism”. 

4. References 

Aretxaga, R. (2003) La ciencia astrobiologica. Un nuevo reto para el humanismo del siglo XXI. Humanismo para 
el siglo XXL Congreso Internacional (Bilbao, marzo 2003). Proceedings (CD-Rom), University of Deusto, 

Billingham, J., Heyns, R., Milne, D., Doyle, S., Klein, M., Heilbron, J., Ashkenazi, M., Michaud, M., Lutz, J. and 
Shostak, S. (eds.) (1994) Social Implications of the Detection of an Extraterrestrial Civilization, SETI Press, 
SETI Institute, California. 

Chela-Flores, J. (1998) Search for the Ascent of Microbial Life towards Intelligence in the Outer Solar System. In: 
R. Colombo, G. Giorello and E. Sindoni (eds.) Origin of the life in the universe. Edizioni New Press, Como, 
pp. 143-157. 

Chela-Flores, J. (2001) La astrobiologia, un marco para la discusion de la relacion hombre-universo. Principia 
(Universidad Centro Occidental L. Alvarado, Barquisimeto, Venezuela) 18, pp. 12-18. 

Chela-Flores, J. (2003) Marco cultural de la astrobiologia. Letras de Deusto (University of Deusto, Bilbao, Spain) 
98, Vol. XXXIII, January-March, pp. 199-215. 

Norton, B. G. (1984) Environmental Ethics and Weak Anthropocentrism, Environmental Ethics, 6, pp. 131-148. 

Dick, S. J. (1984) Plurality of Worlds: The Origins of the Extraterrestrial Life Debate from Democritus to Kant. 
Cambridge University Press. 

Tough, A. (ed.) (2000) When SETI Succeeds: The Impact of High-Information Contact, Foundation for the Future, 
Washington, USA. 



Centre Alexandre Koyre (CNRS-EHESS-MNHN-UMR 8560) 
Museum national d’Histoire naturelle, 57 rue Cuvier — F-75005 
Paris — France 

1. Introduction 

The German naturalist Ernst Haeckel (1834-1919) was probably the most prolific writer on 
the subject of the origin of life in the late 19th century. He was well-known for his monistic 
philosophy (monism) in which all phenomena stood in causal relation and all historical de- 
velopments were strictly continuous (Kamminga, 1980). All of Haeckel’s writings stressed 
the fundamental unity of the living and the non-living world. Haeckel was one of the most 
ardent protagonists of Darwin in Germany and his monism was clearly inspired by the 
theory of evolution. Haeckel transformed the doctrine of evolution into a monistic system 
in which an abiogenic origin of life was a major part (Farley, 1977). 

Haeckel’s opinion about the origin of life was directly dependent on his philosophy 
and on his view of the nature of life. His description of the organization of the simplest 
organisms (Monera), as made of only one substance, led him to adopt the general idea 
of abiogenesis (living material coming from inorganic substance). Regarding a genuine 
abiogenesis, this idea became a logical postulate of the theory of biological evolution and 
of the concept of the unity of nature. Therefore, Haeckel supported the thesis of archigonia 
(genuine abiogenesis), a past process that would have occurred during the early evolution 
of the planet. 

However, partly because of the extreme simplicity of his Monera, Haeckel also believed 
in a continuous spontaneous generation for very primitive biological material in accordance 
with a process of present-day-ai>iogeneiis taking place in the deep sea beds. 

In this paper, we have analyzed the following writings of Haeckel: 

- Generelle Morphologic der Organismen (General Morphology of Organisms) 

- Natiirliche Schopfungsgeschichte (Natural History of Creation) (1868) 

- Die Weltrdthsel (The Riddles of the Universe) (1899) 

- Die Lebenswunder (The Wonders of Life) (1904) 


J. Seckbach et al. (eds.), Life in the Universe, 349 - 352 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. The Unity of Nature 

Haeckel explained the whole living world by means of his monistic philosophy; a unitary 
notion of nature in which matter was supposed to evolve from a primitive cosmic condition to 
a complex biological state: a vast, uniform, uninterrupted and eternal process of development 
occurring throughout all nature. According to Haeckel, this idea was itself the fruit of the 
positive results of the sciences. 

From Haeckel, the unity of nature (organic and inorganic) was supported by a general 
doctrine of development. This doctrine was directly dependent on the theory of biological 
evolution and on the mechanism of natural selection (this last mechanism gave an important 
nonteleological explanation for this development) (Farley, 1977). The main points resulting 
from the monistic philosophy are the following ones: 

- There is no fundamental distinction between the living and the non-living world. 

- There is continuity between them. 

- The same “natural” laws rule the mineral and the organic worlds. 

- The origin of life links together the mineral and the organic worlds. 

3. What is Life? 

The consequences of the monistic philosophy of the unity of nature led Haeckel to defend 
precise point of views about the nature of life. Haeckel deduced from the experiments 
of organic chemistry that all elements found in living organisms were also present in the 
inorganic domain and that carbon (in combination with H, O, N, P, S) was the element 
essential for building proteins (Haeckel described his carbon theory in General Morphology 
of Organisms). He upheld the idea that life depended on the properties of carbon. Proteins 
(or protoplasmic substances constituted mainly by carbon) were the basic components of 
life. Life was the result of physicochemical processes based on the properties of proteins. 
Life amounted to physicochemical actions but living organisms represented a specific state 
of matter: life resulted from combinations formed by carbon and these combinations, in 
interaction with water, led to a specific state, neither solid nor liquid, but a semi-fluid or 
viscid state. 

The theory of the unity of nature included the concept that life was not a qualitatively new 
principle of evolution and then, that life didn’t display any emerging properties. According 
to Haeckel, explaining the phenomenon of life was no more complicated than explaining 
the physical properties of the inorganic matter. In The wonders of Life, Haeckel went even 
further: the theory of the unity of nature implied that life could just as well has been found 
in any organic as inorganic substances. 

4. The Origin of Life 

In Haeckel’s books, the term “spontaneous generation” holds a specihc meaning: “spon- 
taneous generation” inferred in fact the idea of a continuity between the organic and the 


inorganic worlds, and, in Haeckel’s view, this term was equivalent to ‘"archigonia” (or a 
genuine abiogenesis). About archigonia, Haeckel wrote; “under conditions quite different 
from those today, the spontaneous generation which now is perhaps no longer possible, may 
have taken place” (Natural History of Creation, vol 1, p. 342). In short, and according to 
Haeckel, studying the origin of life consists in two major points. The first point is: studying 
the simplest organisms. In General Morphology of Organisms and in Natural History of 
Creation, Haeckel claimed that the most primitive organisms (such as the Monera) were 
“undifferentiated, anucleate, naked pieces of albuminous jelly, far simpler in construction 
than a simple cell” (Farley, 1977). He concluded that the first living organisms on Earth 
were such “homogeneous, structureless, formless lumps of protein or Monera, similar to a 
Protoamoeba.” (General Morphology of Organisms, p. 179, quoted in Kamminga, 1980). 
The second point is: studying the natural cosmology of the Earth with the help of the global 
concept of mechanical causes and evolutionary processes. 

Haeckel wondered about the spontaneous generation from inorganic matter in the past. 
Where do the first ancestral organisms come from? Haeckel answered this question with 
the help of the following hypotheses and theories; the theory of descent — including the idea 
of adaptation and spontaneous generation (Lamarck), the notion of heredity and natural 
selection (Darwin), the principles of cosmogony ruled by mechanical causes (theory of 
evolution applied to the universe and to the celestial bodies, from Kant, Laplace, Herschel). 
Haeckel reached the following conclusions; 

- The characteristic environmental conditions for the primitive Earth were perpetual 
rains, lower temperatures, and a specific electric state of the atmosphere. 

- The major steps leading to the formation of living organisms were the first appear- 
ance of liquid water on the surface and the presence of a huge amount of carbon as 
carbonic acid mixed with the atmosphere. 

- Life started on the Earth at a well-defined period in the past. 

But nevertheless, Haeckel regretted deeply that no experiment regarding archigonia had yet 
been attempted in laboratory. 

5. Criticism of Haeckel’s Theory 

Many criticisms were put forward about Haeckel’s theories, all of these theories depending 
on his Monism. One of the most scathing comments has come from Carl Semper, professor 
of zoology and comparative anatomy in Germany. According to Semper, neither the theory 
of archigonia, nor the theory of origin of life, expressed with the help of carbon theory, 
could be checked with observational experiments. Moreover, Semper considered that the 
protoplasmic theory — as well as the carbon theory — was a simplified theory in comparison 
with what could be the explanation of life. Hence, the question of the origin of life seemed to 
be reduced to a mechanical and physical problem and the emergence of the first organisms 
was considered as an epiphenomenon of matter’s evolution. 

Haeckel defended himself against the first criticism in claiming that the problem of the 
origin of life — as well as the whole evolutionary biology — was an historical science that 
couldn’t follow the model of the exact sciences (such as Physics or Mathematics). 


Concerning the second criticism, Haeckel thought that a mechanical explanation did 
not necessarily involve a full reduction to physical processes. He criticized the so-called 
exact method in embryology on the grounds that it attempted to reduce complex historical 
processes to simple physical phenomena. In fact, Haeckel included historical explanations 
in terms of evolutionary development under the general heading of mechanical explanations 
(Kamminga, 1980). 

6. Conclusion 

Regarding the problem of the origin of life, Haeckel could be considered as a forerunner 
in many points: in order to explain the origin of life, he clearly proposed a past process 
{archigonia) occurring in a completely different environment from the present one. His 
theory contained the premises of the idea of chemical evolution, since the suggested steps 
leading to life are integrated into a broad evolutionary process including geology and chem- 
istry. The origin of life is included in the history of the Earth, and therefore, very long spans 
of time are suggested to favor the transition from inert to living matter. From the episte- 
mological point of view, he asserted that the problem of the origin of life was an historical 
problem that couldn’t be solved in the same way as (for instance) problems of Physics. 
However, perhaps we could reproach Haeckel for having: 

- underestimated the complexity of living matter and therefore having considered the 
transition from inert to living matter to be much too easy. 

- kept the solution of a continuous and present-day spontaneous generation since this 
transition would be so easy and natural. 

- used too much theory instead of practice, and hnally having founded a philosophy 
more than a scientific theory. 

7. References 

Farley, J. (1977) Spontaneous Generation Controversy from Descartes to Oparin, The Johns Hopkins University 
Press, Baltimore and London. 

Girard, J. (1874) Les explorations sous-marines, Savy, Paris. 

Haeckel, E. (1866) Generelle Morphologie des Organismen, G. Reimer, Berlin. 

Haeckel, E. ( 1 874) Histoire de la creation des etres organises d ’apres les lois naturelles, Conferences scientifiques 
sur la doctrine de revolution en general et celle de Darwin, Goethe et Lamarck en particulier, trad. C. 
Letoumeau, C. Reinwald, Paris. 

Haeckel, E. (1902) Les enigmes de Vunivers, trad. C. Bos, Schleicher Freres, Paris. 

Haeckel, E. (1907) Les merveilles de la vie : etudes de philosophie biologique pour servir de complement aux 
Enigmes de Vunivers”, Schleicher Freres, Paris. 

Kamminga, H. (1980) Studies in the History on the Origin of Life from 1860, Thesis for the degree of Doctor of 
Philosophy, Department of History and Philosophy of Science, Chelsea College, University of London. 

Raulin-Cerceau, F. (2004) Historical Review on the Origin of Life and Astrobiology, In: J. Seckbach (ed.) Origins: 
Genesis, Evolution and the Diversity of Life, Kluwer Academic Publishers, Dordrecht, The Netherlands, in 



^ Facultad de Ciencias, UNAM Apdo. Postal 70-407 Cd. Universitaria, 
04510 Mexico, D.F., MEXICO, ^Instituto de Biotecnologi'a, UNAM, Apdo. 
Postal 510-3 Cuernavaca, Mor., 62250 Mexico and ^ Instituto de Ciencias 
Nucleares, UNAM Apdo. Postal 70-543 Cd. Universitaria 04510 Mexico, 
D.F, Mexico. 

I. Introduction 

Based on Pfliiger’s proposal on the role of CN-containing derivatives in biological catalysis 
(Pfliiger, 1875), Alfonso L. Herrera developed in the late 1920’s the sulfocyanic theory of 
the origin of life (Herrera 1942). According to this idea, the physical structure of cellular 
plasma was derived from sulfur- and CN-containing compounds that formed a molecu- 
lar matrix within which the primordial fixation of CO 2 took place via its reduction to 
H 2 CO. 

As described in his extensive bibliography (Beltran, 1968), Herrera achieved the for- 
mation of microscopic structures, which he claimed were comparable to cells, due to their 
growth, motility, and osmotic properties. He promptly divided then into two major groups: 
(a) colpoids, which were produced when olive oil, gasoline, and other complex molecules 
were used; and (b) sulphobes, which resulted from the mixture of NH 4 SCN and H 2 CO 
(Herrera, 1942). After many trials, Herrera found that the best starting material for the 
formation of his sulphobes was ammonium thiocyanate, which he dissolved in formaline 
and spread in thin layers until evaporation. According to Herrera, the reactions of these 
precursors gave rise not only to several kinds of cell-like microstructures, but also to (a) 
starch; (b) two uncharacterized amino acids; (c) globules of red, green and yellow pigments; 
and (d) what he described as a “proteinoid condensation product” (Herrerra 1942). 

As shown by photocopies of some of his laboratory notes (available upon request), by 
1933 Herrera was convinced that he had achieved the synthesis of glycine, cysteine and 
cystine. The formation of these compounds, which Herrera synthesized using formaldehyde 
and ammonium thiocyanate as starting materials, were based on the glycine synthesis from 
formaldehyde and potassium cyanide reported by Klages (1903) and Ling and Nanji (1922). 
Although Herrera (1942) mentioned the synthesis of “starch, and at least two amino acids”, 
he did not list them nor characterize the other products he obtained. Here we attempt to 
do so, based on the repetition of some of his experiments and the use of modern analytical 


J. Seckbach et al. (eds.), Life in the Universe, 353 - 356 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


2. Materials and Methods 

We first mixed 20 ml of 37% formaldehyde (0.05 M final) with 36 g of ammonium chloride 
(0.067 M final) and put this solution into a three-mouth flask that was kept on ice. The mixture 
was stirred all the time with a mechanical stirrer. We then prepared a 0.055 M ammonium 
thiocyanate solution that was poured for 30 min with a separator funnel. When half of the 
thiocyanate solution was added, 25 ml of glacial acetic acid was dropped and the solution 
was stirred for two more hours. The temperature was always kept below 10° C. A precipitate 
was formed with yellow and white crystals. The mixture was filtered and the crystals were 
air-dried. By a fractionated precipitation, we obtained two more precipitates (the second one 
contained yellow crystals, and the third one yellow and white crystals that were separated). 
Based on their infrared spectra, we decided to work with the precipitate 1 and precipitate 3 
white crystals. These were analyzed by infrared spectroscopy, a size-exclusion separation 
method, and HPLC, using a Beckman Instruments HPLC series chromatograph. The column 
used was a Cig with a particle size of 5 |x. The analyses were done at room temperature at 
a wavelength of 340 nm. The retention time of various amino acids was determined using 
a Beckman reference mixture. The fractions of precipitates 1 and 3 were hydrolyzed with 
sequential grade HCl (Pierce), acetic acid for HPLC and water HPLC grade, derivatized 
with ortho-ophtaldehyde (Lindroth and Moppen, 1979) and analyzed for the presence of 
amino acids (Ladron de Guevara et al, 1985). In order to identify the amino acids that 
could be present in the reaction mixture, the white crystals of precipitates 1 (in two runs of 
500 mg each) and 90 mg of precipitate 3 were first purified by a size exclusion separation 
method using a SP-sephadex 25 column. 

3. Results 

The HPLC chromatograms shown in Figure 1 indicate the presence of several compounds 
whose retention times correspond to glycine, alanine, cysteine, and methionine. Of these, 
only cysteine and methionine are sulfur containing amino acids. 


Figure 1. Size exclusion separation of products from precipitate 1, using a SP-Sephadex cm-25 column. Peak 
1 corresponds to the thiocyanate ion that did not react. Peaks 2 to 6 were analyzed separately for amino acid 
content. HPLC identification of 1, glycine; 2, alanine; 3, cysteine; 4, methionine. Amino acids were identified 
by their retention times as described in the text. 


Although we analyzed standard samples of other sulfur-containing amino acids, such 
as taurine and cystine, the peaks obtained in the chromatograms do not correspond to their 
retention times. Other unidentified peaks in the chromatogram could correspond to non- 
proteinic amino acids. The amino acid formation yield was low and was determined by 
the electronic integration of the peak area (Perezgasga et al., 2004). The same amino acids 
were observed in both the hydrolyzed and non-hydrolyzed fractions, although the yield was 
higher in the former one. 

4. Discussion and Conclusions 

Like many of his contemporaries, Herrera was convinced that the first living beings had 
been autotrophes. The popularity of Pfliiger’s (1875) ideas on biological catalysis had led 
Herrera to believe that CN derivatives played an essential role in biochemical processes 
and, hence, that cyanogen and its derivatives must have been present at the origin of life. 
Led by the schemes which suggested at the time that H 2 CO was a central intermediate 
in the photosynthetic fixation of CO 2 , Herrera attempted the laboratory formation of an 
autotrophic protoplasm by mixing the precursors he thought were essential for a minimal 
living system. Thus, it was not because of foresight that he employed compounds which 
are nowadays recognized as potential components of the prebiotic environment. Instead, he 
should be recognized as a careful worker, whose deep knowledge of the major theories of 
his contemporaries led him to study the origins of life within the framework of his times. 

Since Herrera was following the reactions described by Klages (1903) and Ling and 
Nanji (1922), he was actually performing a variation of the Strecker synthesis, in which 
ammonium thiocyanate could take the place of NH 4 CN, and where the hydrolysis of the 
nitrile was achieved by boiling with a highly concentrated solution of barium hydroxide 
(Ling and Nanji, 1922). Our results suggest that in the experiments which we have performed 
following the procedures described by Herrera, four amino acids were synthesized; glycine, 
alanine, cysteine and methionine, with a total yield of 2%. Alanine was the most abundant 
amino acid in all samples analyzed. 

The preliminary results presented here suggest that a variation of the Strecker synthesis 
involving formaldehyde and ammonium thiocyanate could lead to low yields of amino 
acids, including sulfur-containing amino acids. Alternatively, it is possible that the amino 
acids reported here, are the outcome of an hydrolysis of oligomers that could be formed by 
the self-condensation of SCN, by a mechanism equivalent to that described by Ferris et al. 

Although the starting materials used by Herrera were determined by his autotrophic 
hypothesis on the origin of cells, our results show that his experiments may provide in- 
sights on the abiotic synthesis of sulfur-containing amino acids within the framework of a 
heterotrophic emergence of life. 

5. Acknowledgements 

We are indebted to Arturo Becerra for technical assistance. A PAPIIT grant (ES 116601) 
to A.N. and DGAPA-UNAM PAPIIT IN 1 11003-3 to A.L. support from CONACyT grant 
(I36264-N) was provided to L.P 


6. References 

Beltran, E. (1968) Alfonso L. Herrera (1868-1968): Primera figura de la Biologia Mexicana. Revista de la Sociedad 
Mexicana de Historia Natural. 29 , 37-91. 

Ferris, J. R, Joshi, P. D., Edelson, E. H., and Lawless, J. G. (1978) HCN: a plausible source of purines, pyrimidines 
and amino acids on the primitive Earth. J. Mol. Evol. 11 , 293-3 1 1 . 

Herrera, A.L. (1942) A new theory of the origin and nature of life Science 96 , 14. 

Klages, A. (1903) Ueber das methilamino-acetonitril. Berichte der deutschen chemischen Gesellschaft 36 , 1506. 

Ladron de Guevara, O., Estrada, G., Antonio, S., Alvarado, X, Guereca, L., Zamudio, F. and Bolivar, F. (1985) 
Identification and isolation of human insulin A and B chains by high-performance liquid chromatography. 
J. Chromatogr. 329 , 428. 

Lindroth, P. and Moppen K. (1979) High performance liquid chromatographic determination of subpicomole 
amounts of amino acids by precolumn fluorescence derivation with 0-ophtaldehyde. Anal. Chem. 51 , 1667- 

Ling, A.R. and Nanji, D.R. (1922) The synthesis of glycine from formaldehyde. Biochem. J. 16 , 702. 

Pfliiger, E. (1875) Ueber die physiologische verbrennung in den ledendigen organismen. Arch. Gesam.Physiol. 
10 , 641-644. 

Perezgasga L., Silva E., Lazcano A. and Negron-Mendoza A. (2004) A reexamination of Alfonso Herrera’s 
sulfocyanic theory on the origin of life. Journal of Astrobiology (in press). 



^Department of Plant Biology, Southern Illinois University, Carbondale, 
Illinois 62901 USA; ^Bahn Biotechnology Co., RR2, Box 239A, 

Mount Vernon, Illinois 62864 USA. 

1 . Introduction 

The discovery of proteinoids (thermal proteins; branched proteins) in the 1950s and pro- 
tocells there from, filled the gap between physical/chemical and biological evolution. The 
ease in finding amino acids in nature for the autocatalytic synthesis of branched proteins 
(self-ordering) and the ease of finding water in which these macromolecules would form 
protocells (self-assembly) made the proteinoid theory appealing for those interested in find- 
ing a model for the synthesis of living cells (Fox, 1988) and those seeking a candidate system 
for the origin and early evolution of life (Pappelis, et al, 2001). We worked with Sidney 
W. Fox and his associates. Together with Fox, we moved his “model” into biology as the 
branched protein-first paradigm to explain the origin of chemical and biological life. We 
inferred the pathways in the early evolution of protolife to provide new opportunities for 
experimental verification. 

2. Scientific Determinism 

“The night sky of my youth has been explored to the outermost distance and earliest be- 
ginnings of the universe (de Duve, 2002, p. vii):” i.e., big bang — > elementary particles ^ 
atoms — > compounds — > life [= Cosmic evolution (Chaisson, 2001)]. Life emerges as 
chemical life (branched proteins) that yields biological life (branched protein protocells) 
(Fox, 1988; Pappelis, et al, 2001). We infer (believe): the Universe (energy, matter, time, 
etc.) is real; Cosmic laws, discovered by scientists, govern the evolutionary activities of the 
Universe; life obeys Cosmic laws; and, the collective minds of our species can comprehend 
the Universe (scientism; scientific determinism). 

3. Philosophical and Theological Views That Conflict With Scientific Determinism 

Some theists and deists believe that the Natural Laws [“the skeleton of the Universe” (Trefil, 
2003) that existed prior to the Universe and extended into its time] are “God given”. Some 


J. Seckbach et al. (eds.), Life in the Universe, 357 - 360 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


wrote: God acted, created the Universe: ‘“And the Earth brought forth’ life. (Gen. 1:12)’’ 
[sic] (Schroeder, 1998, pp. 5, 85). 

Thus, this origin (and evolution) of life — implies Natural Laws at work. Others wrote: 
An impersonal God would not direct events in the Universe. “The Earth itself had within 
it the (necessary) special properties (self-organization and/or catalysts) to encourage the 
emergence of life. There is no biblical mention of a special creation for the origin of life 
(Schroeder, 1998, pp. 29, 85).’’ (See also, Armstrong, 1993, p. 355.) 

Religious writings are seen by many as inspirational rather than documents for literal 
interpretation. However, deistic (impersonalized God) thinking is now seen in the Anthropic 
Principle: “Large numbers of apparent coincidences existed between things (Universal 
constants) and persuaded many a philosopher, theologian and scientist of the past that none 
of this (Natural Laws) was an accident. The Universe was designed with an end in view. 
This end involved the existence of life — perhaps even ourselves — and the plainness of the 
evidence for such design meant that there had to be a Designer (Barrow, 2002, p. 157).’’ 
Agnostics say that following this type of logic is going beyond the data (insufficient to prove 
the existence of God). Atheists claim there is no logic for such a belief since God does not 
exist in their minds (Armstrong, 1993). 

Many humans retain the Determiner-view (personalized God; caring Creator of Heaven 
and Earth and all things visible and invisible) (based on the argument from design). The 
belief includes: the “something” that preceded the Universe was/is God. 

Scientists generally limit their beliefs to events in the Universe and some claim: — 
strong evidence (data) to support a belief in Cosmic evolution does not prove nor disprove 
the existence of a conscious Determiner (Creator; God). Lundamentalism and creationism 
exhibit religious preferences not considered to be science (Armstrong, 1993, Armstrong, 
2000 ). 

4. Discussion 

“Evolution (of the Cosmos) is a synthesis of determinism and chance, and this synthe- 
sis makes it a creative process. — Eormation of the precursor molecules of life’s origin 
provides — an illustration of the limited role of chance in Nature” — “ — the soupy organic 
matter trapped in this (Miller’s) chemical evolutionary experiment always yields the same 
kinds and proportions of amino-acid-rich, protein-like compounds — and in approximately 
the same relative abundances found embedding meteoric rocks and composing living or- 
ganisms (Chaisson, 2001, p. 37).” Chaisson continues by describing other sources of these 
compounds (boiling, sulfurous pools; hot, mineral-laden deep-sea volcanic vents; interstel- 
lar space via comets or meteorites). We could suggest improvements in his review but the 
point is that if the reactants were “forming and reforming into larger molecules by chance 
alone, that is, in the hypothetical case of no forces at all, the products would be a hopeless 
mess comprising billions of possibilities and would likely vary each time. — But the results 
show no such chemical diversity, nor does life at the biochemical level. Specificity and re- 
producibility are hallmarks of this classic (Miller-type) experiment, ensuring that bonding 
of the amino acids does not occur entirely at random (yielding molecular variations), but 
that certain associations were advantaged while others were excluded (yielding molecular 


selection). — Selective assembly seems more of a rule than an exception — (Chaisson, 2001, 
p. 38).” 

Stereo-electronic forces guide and bond small molecules into larger ones appropriate 
to protolife (amino acids undergoing self-ordering reactions -> branched proteins under- 
going self-assembly reactions -> protocellular life) (Fox, 1988; Pappelis, et al, 2001). 
The natural agents of order tend to tame chance. Molecular variations are important — “but 
natural (molecular) selection is a decidedly deterministic reaction that directs evolutionary 
change (Chaisson, 2001).” Patterns of valid and reliable continuity are clearly evident in 
the past 500 years of data obtained by human, scientific studies of the various levels of 
the Cosmos. Life histories (of chemical and cellular life) are now understood to be real, 
functioning structures of evolving processes. 

Scientists can take samples of the Cosmos for studies (using statistical methods for 
design and analysis) and periodically stop to summarize their findings (develop fheories 
and models). They formulate their future using concepts that arise from their predictive 
(valid and reliable) data. They accept that they cannot know all of the cosmic (moment- 
to-moment emergence of sub-atomic particles in the earliest seconds of the Universe) and 
biological past (99-|-% of the species that emerged according to Darwinian evolution are 
extinct). In this view, long-cherished religious and philosophical tenets have been replaced 
by scientific findings. Yet, many questions remain. (For example, following Stanley Miller’s 
presentation at this conference, Antonio Lazcano asked him about the chemical origin of 
life — “If it wasn’t DNA; and, if it wasn’t RNA; what was it?” Miller replied — “1 don’t 
know.” Our answer would be branched proteins.) 

Modem concepts in Cosmic evolution provided the insights needed to replace older 
explanations (possibly 150,000 years old) about starry night skies. Similarly, the branched 
protein-first paradigm provides continuity within Cosmic evolution: i.e., amino acids -> 
branched proteins (chemical life) biological life. Therefore, we propose that it is most 
appropriate to partition our thinking (and research goals) about: the origins of chemical 
and biological life; the origin of protocells and their early evolution; and, the evolution of 
protocells and the emergence of prokaryotic and eukaryotic life. 

Science is a way of solving problems; its methods apply to what is assumed to be the 
reality of the Universe. Questions concerning morals, value judgments, social issues, and 
attitudes cannot be answered using the science process skills. Science is self-correcting. The 
change in thinking about the sky and Earth was a new paradigm. Similarly, the branched 
protein-first paradigm, developed by Fox (1988) and associates (Pappelis, et al, 2001), has 
changed our thinking about the origin of life and its early evolution on Earth and in the 
Universe. We believe that protolife could not have been discovered except by synthesis. 
Eurther, we do not propose that a deity will “fill the gaps” in the creation and evolution 
theories. Rather, we believe that good science will. 

People understand that science and scientists cannot presently answer all of the problems 
of our time. Scientists believe that they cannot prove nor disprove the soundness of a belief 
in God or Gods. Thus, they prefer to assume that science merely provides one type of 
knowledge — the kind that has predictive value in what is often called the “real” Universe 
(even though most scientists prefer to “assume” that the Universe is real). The religious 
people have faith in their beliefs although there is no data to say their knowledge is either 
valid or reliable. Armstrong (1993) writes that many people around the world believe science 
has replaced (or will replace) religion. 


5. Conclusion 

We conclude; life is a self-sustained chemical system [amino acids from space via microme- 
teorites, from hydro-thermal systems, etc. self-ordering with conformational changes ^ 
branched proteins = chemical life ^ + water -> colloidal suspension ^ phase shifting 
and self-assembly of branched proteins to form wall-membrane vesicles = protocells = bi- 
ological life] capable of undergoing Darwinian evolution (Pappelis, et ai, 2001). We infer 
that the branched proteins that self-assemble into protocells are at the same time multizymic 
structural elements of the wall-membrane boundary involved in protometabolism. As pro- 
tocells enlarge, they form buds (“genetically” active). Branched proteins can be induced to 
form protocells in water (4-60 °C), degenerate (heat to 100 °C), and reform after drying or 
after storage in water (cycles). Microencapsulated macromolecules (branched proteins, etc.) 
and the branched proteins lining the inner surface of the wall-membrane could account for 
the synthesis sites of linear oligo-peptides, oligonucleotides of RNA, and, hnally, oligonu- 
cleotides of DNA (reviewed by Fox, 1988). Since branched proteins might be in the “glass 
state” in meteoritic material in cold space, they may represent a kind of space-traveling life 
(litho-cosmozoa) (Pappelis, et al., 2001). The branched protein-hrst paradigm bridges the 
gap between chemical and biological evolution and functions in the evolution of protocells. 

6. Acknowledgements 

Our memories of Sidney W. Fox have inspired us throughout this work. Aristotel Pappelis 
dedicates his efforts to the memory of Constantine Zahariades, Gerald and Peter Andrews, 
and Reverend Father Nicholas Karras, his hrst teacher of religion and philosophy. 

7. References 

Armstrong, K. (1993) A History of God: The 4000-Year Quest of Judaism, Christianity and Islam. Ballantine 
Books, NY. 

Armstrong, K. (2000) The Battle for God: A History of Fundamentalism. Ballantine Books, NY. 

Barrow, J. D. (2002) The Constants of Nature: From Alpha to Omega — The Numbers That Encode the Deepest 
Secrets of the Universe. Pantheon Books, NY. 

Chaisson, E. J. (2001) Cosmic Evolution: The Rise of Complexity in Nature. Harvard University Press, Cambridge, 
MA, (pp. 37^1). 

de Duve, C. (2002) Life Evolving: Molecules, Mind, and Meaning. Oxford University Press, NY. 

Fox, S. W. (1988) The Emergence of Life: Darwinian Evolution from the Inside. Basic Books, NY 

Pappelis, A., Bahn, P, Grubbs, R., Bozzola, J., and Cohen, P. (2001) From inanimate macro-molecules to the 
animate protocell: In search of thermal protein phase-shifting, in J. Chela-Flores, T. Owen, and F. Raulin 
(eds.). First Steps in the Origin of Life in the Universe, Kluwer Academic Publishers, Dordrecht, pp. 65-68. 

Schroeder, G. L. (1998) The Science of God: The Convergence of Scientific and Biblical Wisdom. Broadway Books, 
NY. (pp. 5, 29, 85). 

Trefil, J. (2003) The Nature of Science: AnA-Z Guide to the Laws & Principles Governing Our Universe. Houghton 
Mifflin, NY 

A Pictorial Overview 


Beach House, Juhu, Mumbai 400 049, INDIA 
chadhams® ma 

A re-capitulation of Trieste Conferences, on Chemical Evolution and Origin of Life from 
their inception in 1992 is presented. An attempt is made to highlight the Scientific, Ed- 
ucational and Cultural aspects (through pictures taken at the six conferences held until 
2000). Participation in the Eirst Trieste Conference held at International Centre for Theo- 
retical Physics (ICTP) in Oct 1992 and now at the Seventh Conference and all the others in 
between has provided the author with a perspective, which is being shared. 

The first Trieste Conference, which was the brainchild of Prof. Abdus Salam and Prof. 
Cyril Ponnamperuma, was held under the joint sponsorship of the International Atomic 
Energy Agency and the United Nations Educational Scientific and Cultural Organisation 
and witnessed active participation by both the founders of this unique Series of Conferences. 
Prof. Julian Chela-Flores, who has been the backbone of this activity eversince, assisted 
them in their efforts. This inter-disciplinary international conference was entitled Chemical 
Evolution; Origin of Life and defined the scope and objectives of this novel effort. 

The second Trieste Conference (Oct. 1993) was entitled Chemical Evolution: Self- 
organisation of the Macromolecules of Life and was dedicated to Cyril Ponnamperuma 
on his 70th birthday. The focal theme of self-organisation was sub-divided into chemical 
aspects, geophysical aspects, biochemical aspects, biophysical aspects and chirality. At this 
conference many of the erstwhile collaborators of Cyril Ponnamperuma participated and 
the proceedings of the conference were edited by Julian Chela-Flores and Cyril Ponnam- 
peruma’s former collaborators namely; Mohindra S. Chadha, Alicia Negron-Mendoza and 
Tairo Oshima. 

The third Trieste Conference (Sept. 1994) was entitled Chemical Evolution; Structures 
and Model of the First Cell and was designated as the Alexander Ivanovich Oparin 100th 
Anniversary Conference. This was the best-attended conference of the three Trieste confer- 
ences till then and the presentations on planetary, extraterrestrial and interstellar conditions 
broke a lot of new ground. The topics covered the beginning of cellular organisation (the 
early paleonotoligical record, physical, chemical and biological aspects of the origin and 
structure of membrane and origin and structure of the cell). 

The fourth Trieste Conference (Sept. 1995) was the first conference of the series, which 
was held after the untimely and sudden demise of Cyril Ponnamperuma, the co-founder 
of this series of conferences. He was involved in the early part of the preparation of this 


J. Seckbach et al. (eds.), Life in the Universe, 361 - 363 . 

© 2004 Kluwer Academic Publishers. Printed in the Netherlands. 


conference but unfortunately was not to live to witness its deliberations. Such is Life! 
The Conference was entitled Chemical Evolution: Physics of the Origin and Evolution. The 
Conference was aptly dedicated to the memory of Cyril Ponnamperuma. There were general 
overview presentations by John Oro on Cosmic Evolution and by Sidney Fox entitled Ex- 
perimental Retracement of Terrestrial Origin of An Excitable Cell: Was it Predictable? The 
sessions covered a broad range of topics e.g. Origins; From Geophysics to Prebiotic Chem- 
istry; Physicochemical Aspects; Biophysical Aspects — General problems & Biomolecular 
Chirality; Evolutionary Aspects; Information Theory: Communication and Instrumentation 
in Exobiology and Mars Exploration. 

In a special session, homage was paid to Cyril Ponnamperuma and excerpts of letters 
received from various academies, institutions and admirers of Cyril Ponnamperuma from 
different parts of the Globe were read out. A touching note received from his wife (Valli) 
and daughter (Roshini) was also shared. 

The fifth Trieste Conference (Sept. 1997) was entitled Exobiology, Matter, Energy and 
Information in the Origin and Evolution of Life in the Universe and was dedicated to the 
memory of Abdus Salam, the co-founder of the Trieste series of Conferences and Director 
of ICTP, who had unfortunately passed away after prolonged illness. This conference had as 
many as 12 sponsors and was largely attended. The highlights were talks by: Chela-Flores 
entitled: Abdus Salam — From Fundamental Interactions to the Origin of Life. The Abdus 
Salam lecture by John Oro entitled: Cosmocological Evolution — A Unifying and Creative 
Process in the Universe. The Cyril Ponnamperuma lecture by Frank Drake, namely The 
Search for Intelligent Life in the Universe. The opening lecture: The Theory of Common 
Descent by Richard D. Keynes and a Public Lecture by Paul Davies entitled: Are We Alone 
in the Universe (?). 

The sessions at this Conference dealt with Matter in the Origin; Energy from Inert 
to Living matter; Information; Early Evolution; Exobiology on Mars and Europa; The 
Interstellar Medium, Comets and Chemical Evolution; Exobiology on Titan; Extrasolar 
Planets and Search for Extraterrestrial Intelligence. 

This Conference was unique in focussing on Exobiology in general and on Comets, 
Planets and the Interstellar Medium in particular. 

The sixth Trieste Conference (Sept. 2000) was entitled First Steps in the Origin of Life in 
the Universe and was dedicated to Giordano Bruno whose intuitive concepts have relevance 
to current enquiries related to the First Steps in the Origin of Life in the Universe. This 
conference had as many as 1 1 sponsors. The conference featured a special lecture by Stanley 
Miller who presented the possibility of Peptide Nucleic Acids as A Possible Primordial 
Genetic Polymer. The Abdus Salam lecture entitled: Physics and Life was delivered by 
Paul Davies and the Cyril Ponnamperuma lecture by J. William Schopf entitled: Solutions 
to Darwin’s Dilemma: Discovery of the Missing Precambrian Records of Life. All the three 
presentations were quite scintillating. 

A new feature of the sixth Trieste Conference was inclusion of a section entitled: 
Historical Aspects which featured work of Sidney Fox (by Aristotle Pappalis), Theories on 
Origins of Life between 1860-1900 (by F. Raulin-Carceau) and Reminiscences: Pont-a- 
Mousson-1970 to Trieste-2000 (by Mohindra Chadha). 

The other main topics of the conference dealt with Life without Starlight and questions 
asked were: Can Life Originate in the absence of Starlight? The other important topics dis- 
cussed were: Is there indigeneous material on Mars? The search for prebiotic and biological 


indicators in the satellites of the outer solar system; New Approaches to the Detection of 
Extraterrestrial Radio Signals and the Implications. In a Pre-Dinner lecture entitled New 
Paradigms Of Seti, Frank Drake brought the audience up to date in this challenging and 
exciting venture of scientific endeavour. 

The Sixth Trieste conference had all the embellishments of the previous conferences 
as envisioned by the two founders (Abdus Salam and Cyril Ponnamperuma). The Keynote 
addresses given by leading researchers in their respective fields were authoritative. Many 
young scientists from both the industrialised countries and those from developing countries, 
coming from different parts of the Globe enriched themselves greatly from their participation 
in this conference as they did in the earlier ones. 

The last Six Trieste Conferences and now the Seventh Conference held to honor Stanley 
Miller for his seminal discovery some 5 decades back have brought together scientists (both 
experimental and theoretical), philosophers and theologians of repute on the same platform. 
In all, nearly 600 participants have benefited from the Trieste Conferences. Unfortunately 
some of the luminaries who participated in the earlier conferences have departed from this 
world and a special mention of their contributions has been made. 

The intellectual flavor of the discussions and many debates has been of a high order and 
the future for these inter-disciplinary international deliberations seems to be very bright. 
Our thanks are due to Julian Chela-Flores, Tobias Owen and Francois Raulin who have 
continued to carry the torch lit by Cyril Ponnamperuma and Abdus Salam still further. The 
sponsors and the organising committee also deserve applause. This tribute to the activities of 
over a decade of Trieste Conferences on Chemical Evolution and Origin of Life is presented 
through a Pictorial Overview. 


ABRAMSON Guillermo 
Centro Atomico Bariloche 
Instituto Balseiro 
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Centre for Space Physics 
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Universita’ di Napoli ‘Federico li’ 

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Research School of Physical Sciences 

D. of Applied Mathematics 

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Bhabha Atomic Research Centre 
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S.N. Bose National Centre For Basic 

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Salt Lake 
700098 Calcutta 

Universidad Simon Bolivar 
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University of Oxford 
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Institute de Ciencias Avanzadas 
Edificio Tlacolulan I Depto 201 
Ignacio Allende 93 
Xalapa 91097 



Institute de Estudios Avanzados — IDEA 

Centro de Biotecnologia 

Apartado Postal 17606 

Parque Central 

Caracas 1015-A 


Centro de Astrobiologia 
(Nasa Astrobiology Institute) 

Ctra. de Ajalvir Km.4 
Torrejon de Ardoz 
28850 Madrid 

Col. Chamilpa 
62210 Cuernavaca 

Universidad Nacional Autonoma 
de Mexico 

Institute de Ciencias Nucleares 
Apdo. Postal 70-543 
Circuito Exterior. C.U. 


04510 Mexico City 
Mexico A39 

RAULIN Erancois 

Universites Paris 7 and 12. of Cnrs 


Eaculte’ Des Science Et Tech. 

61 Ave. General de Gaulle 

94010 Creteil 


Radiotelescopi di Medicina 
AIA Cavicchio 
Via della Eiorentina 
40060 Villafontana (Bologna) 


PLATTS Nicholas Simon 
Carnegie Institution of Washington 
Geophysical Laboratory 
5251 Broad Branch Road. N.W. 

20015 Washington 
United States of America 

PUY Denis 

Observatoire de Geneve 
Chemin Des Maillettes 5 1 
CH-1290 Sauverny 

RAMIREZ {JIMENEZ} Sandra Ignacia 
Centro de Investigaciones Quimicas 
Universidad Autonoma del 
Estado de Morelos 
Av. Universidad 1001 

ROEDERER Juan Gualterio 
University of Alaska 
Geophysical Institute 
P.O. Box 757320 
99775-0800 Alaska 

United States of America 

SALAWU Sule Ola 

Eederal University of Technology 

Biochemistry Department 

P.M.B. 704 

Ondo State 



Consiglio Nazionale Delle 


Ricerche (C.N.R.) 

Istituto di Spettroscopia Molecolare (I.S. 
Via Gobetti 101 
40129 Bologna 

SCHWEHM Gerhard 
European Space Agency (Esa) 


Space Science Department 
Postbus 299 
2200 AG Noordwijk 


the Hebrew University of Jerusalem 



SHAH Tahir K. 

Universita degli Studi di Trieste 

Via Valerio 10 
34100 Trieste 

SHIL Pratip 
University of Pune 
Biophysics Laboratory 
Department of Physics 
411 007 Pune 


Universite de Blida 

Institut Des Sciences Exactes 

Departement de Physique 

B.P. 270 




Rice University 

Department of Statistics, MS 138 
PO. Box 1892 
Houston 77251-1892 

United States of America 

SIMAKOV Mikhail 
M.) Russian Academy of Sciences 
Institute of Cytology 
Tikhoretsky Av. 4 
194064 St. Petersburg 
Russian Federation 

SIMON Istvan 

Hungarian Academy of Sciences 
Institute of Enzymology 

H-1518 Budapest 

New Scientist 
151 Wardour St. 


United Kingdom 


Los Alamos National Laboratory 

X-7, MSF699 

Los Alamos 87545 

New Mexico 

United States of America 


Universitat Salzburg 

Institut Fur Allgemeine Biologic 

Hellbrunner Strasse 34 

5020 Salzburg 


TEWARI Vinod Chandra 
Wadia Institute of Himalayan 

33 General Mahadeo Singh Road 
PO. Box 74 

248001 Dehra Dun 

TORRES AROCHE Leonel Alberto 
Centre For Clinical Research 

34 No. 4501 E/45 Y 47 
Reparto Kohly 
11300 Havana 



TURNBULL Margaret C. 

University of Arizona 
Steward Observatory 
933 N. Cherry Ave. 

Tucson 85716 

United States of America 

UNAK (DARCAN) Perihan 

Ege University 

Institute of Nuclear Sciences 


35100 Izmir 


VAN DUNNE Hein Johan Francois 
Kluwer Academic Publishers 
PO. Box 17 
3300 A A Dordrecht 


15 Rue Notre Dame des Pauvres 
BP 20 

54501 Vandoeuvre les Nancy 

VANCE Steven 
Institut fuer Planetologie 
Wilhelm-Klemms Strasse 10 
Munster 48149 

VIDYASAGAR Pandit Bhalchandra 

University of Pune 

Department of Physics 


411 007 Pune 


VIEYRA Adalberto 
Universidade Federal Do 
Rio de Janeiro 
Institute de Biofisica 
Ibccf-Ccs-Ilha Do Fundao 
22000 Rio de Janeiro 

VLADILO Giovanni 
Osservatorio Astronomico 
di Trieste 

Via G.B. Tiepolo 1 1 
34131 Trieste 

WANG Wenqing 
Beijing University 
{University of Peking} 

Dept, of Technical Physics 
100871 Beijing 
People’s Republic of China 

WARD Peter D. 

University of Washington 
Astrobiology Program 
Department of Biology 
PO. Box 357242 
Seattle 98195-7242 

United States of America 

WESTALL Frances 

Centre National de La Recherche 


Centre de 

Rue Charles Sandron 
4507 1 Orleans Cedex 2 


16S rRNA gene, 208, 209, 214 
IP/Halley, 187, 204 
2175A bump, 171, 172 
2PCF, 36, 38, 39 

ab initio, 122, 149, 150 

ahiogenesis archigonia, 351 

absolute asymmetric photochemistry, 185 

absorption-line spectroscopy, 169 

acetate, 161-164 

acidophiles, 141 

ACP, 279, 280 

advanced civilizations, 173, 174, 176, 253 
advancement, 194, 322, 225 
aerosol analogues, 280-284 
aerosols, 4, 5, 152, 276-284, 287, 290, 291 
airborne bacteria, 214 
Akilia Island, 64, 65, 239 
alanine, 10, 12, 13, 15, 80-82, 109, 191, 214, 
246, 354, 355 
ALH84001, 141 
aliphatic hydrocarbons, 283 
alkaliphiles, 141 

amino acid, 79, 81, 83, 86, 90, 107, 117, 119, 
121, 122, 124, 127, 1287, 1 133, 134, 
136-136, 149, 152, 154, 183-186, 257, 
354, 355,358 

amino acid polymerization, 82, 83 
amino acid sequence analysis, 133 
amino acid sequence motifs, 107 
amino acids sequences reconstruction, 127 
amino acids, chronological order, 127, 128 
ammonium thiocyanate, 353-355 
amphiphile. 111 
anastrophe, 110 

ancient microfossils, 221, 222, 240 
Antarctica, 141, 257, 259, 260, 264 
Anthropocentrism, 347, 348 
anti-anthropocentric, 345 
anti-greenhouse, 276 
Apex chert, 63, 66, 243, 247, 248 
Aptamer, 116, 118 
Archaebacteria, 207, 273 
aromatic hydrocarbons, 248, 283 

artificial intelligence, 319, 321, 323-325 
asteroids, 178, 184, 201, 245 
astrobiological biocentrism, 346, 348 
astrobiologists, 263, 347 
astrobiology, 27, 49, 67-69, 100, 106, 135, 
138-140, 142, 169, 170, 180, 191, 195, 
216, 217, 220, 222, 224, 244, 247, 260, 
269, 272, 280, 282, 284, 306, 314, 320, 
322, 323, 325-327, 330, 345-348, 352, 


astrochemistry, 59, 62 
Astrophysical Virtual Observatory, 176 
asymmetric synthesis, 74, 76, 77 
Atacama Desert, 21 1-216 
atmospheric composition, 253 
autocatalytic, 9, 73-76, 164, 357 

Bacteria, 43, 100, 127, 128, 130, 132-134, 136, 
137, 139-142, 213, 214, 222, 239-241, 
243, 244, 253, 255-257, 259, 272, 273, 
294, 295, 346 

bacterial waste, 257-259, 266, 272, 330 
bacteriomorph, 240 
barophiles, 141 
Basic Reaction (BR), 294 
Beagle 2, 4, 186, 227-230 
Benzene, 33, 213, 277, 283 
biased probability, 96 
biased process, 123 
biased synthesis, 93, 94 
bifurcation-type mechanism, 79, 81 
bioastronomy, 138, 176, 220, 296, 302, 305, 
308, 326 

biocentrism, 330, 345-348 
biocentrism, astrobiological, 346, 348 
biocentrism, crisis of, 348 
biocentrism, ethical, 345 
biocentrism, role of, 347 
biochemistry, 3, 7, 23, 27, 135, 136, 138, 241, 
328, 342, 344 
biofilm, 240-242 
biogels, 270, 271 

biogenic elements, 55, 169, 170, 172, 328 
biogeocentrism, 348 



biogeochemical cycles, 294—294 
bioindicators, 135 
bioinformatics protocols, 133 
biological life, 321, 357, 359, 360 
biological universe, 319-326 
bio-molecules, 191, 193-195, 197, 198 
biopotential, 65, 273 
biosedimentology, 249, 250 
biosignatures, 63, 65, 219, 340, 365, 372, 322, 

biosphere, 48, 69, 81, 103, 120, 121, 124, 128, 
148, 156, 164, 180, 186, 204, 217, 219, 
220, 260, 265, 266, 269, 272, 296, 314 
Boltzmann equation, 86 
branched protein-first paradigm, 357, 359, 360 
branched proteins, 357, 359, 360 
bulge, 21, 57, 173-176 
Buxa Dolomite, 249, 250 

Callisto, 4 

Cambrian, 222, 243, 244, 247, 249, 329, 343, 

Cambrian fauna, 329 
Cameras, 228-230 
Cape Canaveral, 276 

Carbon, 5, 9, 10, 14, 16, 23, 26, 56-58, 61, 
63-66, 95, 125, 126, 162-164, 171, 183, 
192, 196, 218, 220, 221, 227, 229, 239, 
241, 243-246, 248-250, 253, 254, 258, 
272, 276, 293-296, 350, 351 
carbon chemistry, 23, 26, 61 
carbon isotope, 64, 230, 243, 245, 248, 250 
carbon theory, 350, 35 1 
carbonaceous microfossils, 239 
carboxylic acid, adsorbed, 93 
Cassini, 5, 275, 276, 278-280, 284, 290 
Cassini orbiter, 276 

Cassini-Huygens mission, 275, 276, 278-280, 
284, 290 

catalytic enhancement, 113, 114 
celestial bodies, 139-142, 351 
chance, 9, 108, 110, 135, 174, 253, 331, 337, 
341, 343, 344, 358, 359 
chemical abundances, 55, 168, 172, 201, 204 
chemical equilibrium, 85, 86, 262 
chemical evolution, 3, 5, 7, 9, 40, 55, 57-59, 73, 
77, 79, 93, 95, 96, 110, 117, 135, 146, 148, 

149, 153-157, 163, 164, 167, 168, 
170-172, 180, 183, 195, 196, 236, 293, 
296, 352, 358, 361-363 
chemical flux, 84, 85 
chemical life, 357, 359, 360 
chemical rate, 86 
chemical soup, 33 
chemistry-dominated Universe, 44 
chemoautotrophic organisms, 296 
chemosynthetic ecosystems, 295 
chiral symmetry breaking, 73, 74, 76, 77 
chirality, 73, 74, 76, 77, 79, 81, 83, 91, 121, 122, 
149, 152, 164, 186, 193, 266, 270, 278, 
279, 361, 362 
chondritic asteroids, 201 
Christian tradition, 322 
chromicyanide, 153-156 
chronological order of amino acids, 127, 128 
circularly polarized electromagnetic radiation, 
73, 75, 184 

circumstellar disks, 167, 183 
CIRS, 278, 279 

civilization, 172-174, 176, 253, 256, 284, 299, 
301, 308, 323-326, 335-337, 347, 348 
clay, 83, 93-96, 145-149, 156, 160, 218, 219, 

clay minerals, 93, 96, 146-149, 218, 219 
closed ecosystem, 295 
CLUSTALW, 128, 133, 134 
Clusters of Othologous Groups (COGs), 127, 

CO 2 , 9, 10, 12, 14, 16, 24, 64, 95, 125, 126, 
140-142, 183, 184, 188-190, 214, 233, 
234, 254, 256, 257, 276-278, 293-295, 
353, 355 

coarse graining, 32-35, 37, 49 
coenzymes, 115-118 
cofactors, 118, 183, 185 
collaborative researches, 67 
collision rate, 86 
colpoids, 353 

comets, 15, 26, 68, 178, 184, 186, 189, 190, 

201, 204, 245, 246, 275, 293, 296, 328, 
329, 358, 362 

common ancestor, 48, 93, 117, 120, 127, 
129-132, 270, 295,314, 345 
compartmentalization, 83 


competition, 112 

complexity, 17, 23, 28, 33, 37, 38, 40, 43^5, 
47, 49, 59, 73, 97, 99, 100, 103, 109, 113, 
114, 149-151, 193, 276, 313, 325, 

352, 360 

compositional information, 112 
composomes, 112-114 
computer simulations. 111 
contingency, 135, 137, 138, 327, 330 
convergent evolution, 117, 135-138, 171, 
265-267, 272, 273,314, 330 
cooperation, 68, 186, 275, 347, 348 
COSAC, 183, 185, 186 
cosmic chemistry, 17, 23 
cosmic evolution, 3, 17, 49, 97, 100, 110, 
319-321, 323, 325, 328, 357-360, 362 
cosmic imperative, 40, 49, 327, 330 
cosmology, 17, 23, 26, 55, 303, 308, 319, 321, 
326, 351 

cosmotheology, 325 

Crater Daedalus, 303-306 

Crater Saha, 303, 305, 306 

creationism, 342, 358 

cryovolcanism, 277, 278 

crystallization, 74, 77 

cultural evolution, 311, 319-321, 323-326 

cyanopolynes, 279 

Cyanaidium caldarium, 140-142 

C“-tetrasubstitute a-amino acids, 121, 122 

Damped Lyman a (DLA) systems, 167-172 
dark energy, 20, 319 

Darwinian evolution, 30, 50, 99, 134, 319, 327, 
359, 360 

deep earth biosphere, 217 

definition of life, 30, 180, 269 

dense interstellar clouds, 183, 194-196, 199 

desert, 211,212, 214-216 

desorption, 158, 197 

destiny of life, 319-323, 325, 327, 330, 346 

diamino acids, 184, 185 

dicarboxylic acids, 213 

dielectric properties, 279 

Diels-Alder type reactions, 283 

disk, 21, 55, 57, 167, 168, 172-176 

DISK, 279 

distant technology, search for, 299 

DNA, 27, 32, 62, 83, 89, 90, 105, 106, 109, 
116-118, 128, 129, 132, 145-148, 179, 
180, 184, 194, 198, 209, 213, 214, 254, 
270, 271,359, 360 
DNA chemistry, 32 
DNA molecule, 145, 147 
Drake equation, 319, 323 
dry valley lakes, 257, 259 
Dyson spheres, 173, 174, 176 

Early Archaean, 62, 66, 239, 240, 242-244, 248 
early evolution, 68, 83, 104, 107, 109-111, 114, 
127, 148, 245, 247, 349, 357, 359, 362 
early Universe, 17, 20, 26, 59, 61, 62, 167, 172 
Earth, life on, 4, 51, 53, 66, 93, 109, 111, 120, 
127, 148, 245, 247, 349, 357, 359, 362 
Earth, life outside, 67, 253, 265 
Earth’s atmosphere, 4, 19, 276 
eco-system, 41, 112, 113, 205, 233-235, 257, 
295, 329, 345, 346 

electrochemical reduction of CO 2 , 125, 126 
electronic impact energy distribution function 
( RE DE), 288, 290 
emergence of language, 334 
emergent phenomena, 33, 47 
Emperor Seamounts, 217 
enantiomeric excess, 74-77, 79, 121, 122, 185, 

end of science, 335, 337 
entropic coupling, 84 
environmental biocentrism, 345 
environmental sensors, 229 
environments, 3-5, 15, 23, 45, 67, 83, 120, 135, 
139-142, 148, 151, 157, 159-163, 170, 
172, 177, 179, 180, 207, 209, 210, 215, 
223, 224, 236, 242, 243, 253, 256, 259, 
282, 284, 295, 312, 315, 322, 328, 


epistemological proposal, 343 
ethical biocentrism, 345 
ETI radio signals, 300 
ETI, age of, 323 

Europa, 4, 67, 68, 138, 139, 141, 209, 251, 255, 
257-266, 269, 272, 296, 322, 327, 328, 
330, 362 

Europa, iced surface of, 141, 258, 259, 261, 269 
Europan Ocean, 261, 264, 269 


European Exo/Astrobiology Network 
Association (EANA), 68, 69 
European Exo/Astrobiology Workshop, 67-69 
evolution, 86, 110 
evolution of intelligence, 325, 333 
evolution of the Universe, 17, 23, 27, 37, 39^1, 
47, 50, 59, 97 

evolutionary biomarkers, 330 
evolutionary divergency, 129, 135 
evolutionary pressure, refuges against, 311, 


exo/astrobiology, 67-69, 244, 275, 277, 279, 
280, 282, 287, 296, 306 

exobiology, 48, 67, 69, 487, 228, 248, 260, 267, 
275, 279, 280, 293, 295, 296, 320-322, 
334, 362 

exobiology lander, 228 
experimental setup, 187, 188, 288 
experimental simulations, 14, 94, 190, 287, 


experimental study, 187, 190 
extended sources, 187-190 
Extraterrestiral Intelligence (ETl), 300, 302, 

extraterrestrial, 15, 67, 79, 121, 122, 136, 137, 
139, 141, 205, 209, 210, 222, 244-248, 
253, 257, 260, 266, 275, 297, 299, 301, 
307-309, 311, 314, 321-323, 325, 326, 
329, 333-337, 346-348, 361-363 
extraterrestrial civilization, 323, 325, 326, 
335-337, 348 

extraterrestrial life, 67, 141, 222, 253, 321, 322, 
326, 346-348 

extraterrestrial life, implications of, 322 
extreme environments, 3, 4, 67, 139, 142, 244, 
256, 322 

extremophiles, 139, 141, 142, 210, 230, 244, 


Earside, 303-306 
EASTA, 133, 134 
first genetic material, 183 
first peptides, 105 
fitness parameters, 1 12-1 14 
flavins, 115-118 
fluorescent molecules, 27 1 
flux densities, 201 

flux of water, 85, 86 
formate, 125, 126, 214, 295 
force-field driven interactions, 98 
formic acid, 10, 213, 214 
fossil microbes, 240 
fossil prokaryotes, 240, 241 
EREZCHEM, 262, 264 

Eunction, 22, 23, 25, 31, 35^1, 49, 50, 80, 89, 
95, 106, 109, no, 117, 130, 136, 188, 189, 
196-198, 202, 228, 234, 270, 272, 276, 
287, 289, 290, 305 
functional convergence, 136 
functionalism, 345, 346 

Gaia, 234, 236 

galactic chemical evolution, 57, 168, 180 
Galileo Mission, 4, 327 
Galileo spacecraft, 209 
gamma-ray bursts, 22, 23, 26 
Ganymede, 4, 276 
GARD Model, 111, 112 
gas chromatography, 94, 183, 185, 186, 211, 
213, 227 

gas exchange experiment, 211, 216 
GC-MS, 183-186, 211, 213, 214, 278, 279, 


gene duplication, 127-132 
gene elongation, 131, 132 
genetic code structure, 89, 91 
genotype, 104, 235, 236 
geocentric system, 320 
geocentrism, 347, 348 
geofluid, 277 

geostationary orhit, 303, 306 
genetic code, 

glycine, 12, 14-16, 107, 109, 123, 128, 149, 
152, 191-194, 246, 353-356 
grains, 4, 23, 59, 60, 64, 168, 187, 189, 190, 
196-198, 207 

gravitational lensing, 20, 26 
greenhouse, 253-255, 276, 321 
greenhouse gases, 253, 254, 276 
Greenland, 63-66, 230, 243, 247 

habitability, 170 

habitability zone, 177, 179, 180, 266 
habitable planets, 168, 169, 328 


habitable zone, 3, 168, 172, 178, 180, 254-256, 

habitable zones in the early universe, 172 
habitats, 4, 139, 140, 142, 146-148 
Haeckel, E„ 349-352 
Haeckel’s theory, 351 
halite, 208-210 
haloarchaea, 207-210 
Halohacterium, 208, 209 
Halococcus salifodinae, 208, 209 
halophiles, 141 
HASI, 279 

Hawaiian islands, 219 
HCN polymers, 187-190 
heat, 119, 120 
heat-stability, 120 
Heidmann, Jean, 303, 306 
heliocentric system, 320 
heterotrophic bacteria, 213 
hexamethylenetetramine, 187 
hierarchical dust accretion model, 204 
high red shift data, 328 

high temperatures, 64, 83, 86, 87, 120, 140, 146, 
161, 162, 188, 279 
histidine biosynthesis, 131, 132 
historic opportunity, 348 
homochirality, 73, 76, 79, 81, 83, 121, 122, 152, 

homochirality of life, 121, 122 
Horgan, J., 335-337 
Hubble Law, 17-19 
human language, 333, 334 
human progress, 347 
humanists, 347, 348 
humanities, 348 
humanoids, 311, 313, 314 
Huygens, 5, 275, 276, 278-280, 284, 290 
Huygens probe, 5, 276, 278, 280 
Hydrocarbons, 5, 64, 65, 163, 222, 248, 277, 
283, 287 

hydrogen peroxide, 214, 215 
hydropathy, 80, 91 

hydrothermal, 63-65, 120, 125, 139, 140, 
157-164, 221, 239, 240, 244, 257, 
260-264, 294-296, 322, 329, 330 
hydrothermal systems, 64, 65, 160, 257, 260, 
262-264, 294, 296 

hydrothermal vents, 120, 139, 140, 157-159, 
161-163, 257, 322, 329, 330 
hydrotherms, 125 
hyperthermophiles, 120, 140, 141 

iced surface of Europa, 259 
impact, 119, 141, 185, 204, 228, 230, 245-248, 
254, 256, 262, 264, 279, 280, 290, 
322-324, 327, 337, 348 
Indian Himalaya, 245 
inflationary universe, 17, 18 
information, 97 
information, pragmatic, 98 
information-driven interactions, 99 
infrared spectroscopy, 26, 280, 282, 354 
inorganic pyrophosphate, 107 
in-situ measurements, 257 
intelligence, evolution of, 133, 272, 317, 325, 
327, 329, 330, 333 

intelligent behavior, evolution of, 133, 272, 327, 
329, 330 

intelligent design, 342 

Interferometric Array, 303 

intergalactic clouds, 21 

International Academy of Astronautics, 303, 


International telecommunication Union (ITU), 
305, 306 

interplanetary dust particles, 15, 184, 329 
interstellar clouds, 183, 191-196, 198, 199 
interstellar dust, 4, 149, 167, 170, 186 
interstellar ices, 23, 26, 183, 185, 186, 328, 


intestellar extinction curve, 171 

ion channels, 269-272, 299 

ionizing continuum, 171, 172 

ionosphere, 303 

IRIS, 279 

Isidis Planitia, 228 

ISO, 277, 280 

isotopes, 20, 64, 229, 241, 243 
Isua greenstone belt, 63, 66 

Jupiter Icy Moons Orbiter, 5 

K/T boundaries, 245, 246, 248 
Koko Seamounts, 218, 220 


labeled release experiment, 211,215,216 
laboratory simulation, 14, 277, 280-282, 284, 
287, 291 

labs-on-a-chip, 265 

Lagrangian points L4 and L5, 303, 305 

Lake Chad, 259 

Langragian point L2, 306 

large-scale structure, 17, 20, 39, 41 

laser-induced plasma (LIP), 282, 283 

Last Common Ancestor (LCA), 127, 128, 295 

Late Heavy Bombardment, 65, 152 

Lesser Himalaya, 245-250 

LGN star population, 178 

life outside the Earth, 67, 253 

life-genicity, 177, 179, 180 

life-sustainability, 177, 179, 180 

lifetime of a technological civilization, 323, 324 

lightning, 119, 120, 216, 278, 293 

limb, 304 

lipid world. 111, 112, 114 
liquid water ocean, 257, 296 
lithoautotropic methanogenesis, 257 
LIVE-DEAD kit, 210 
living matter, 44, 45, 120, 256, 352, 362 
living systems, 27-30, 32, 39, 41, 43^9, 93, 
105, 146, 162, 163, 253, 254, 278, 294, 


local entropy production, 84 
long period variables, 176 
Lunar Farside Radio Lab, 303, 304, 306 
Lyman-a, 21, 167, 168, 172, 183 

MACHO, 174-176 
main sequence stars, 173, 174, 176 
Markov chain, 123, 124 
Mars, 4, 10, 67-69, 139, 141, 186, 209,211, 
216-220, 223-225, 227-231, 233-237, 
243, 244, 247, 248, 254-256, 263, 264, 
275, 296, 308,314, 322, 362 
Mars Express, 4, 228 
Mars analogs, 217 
Mars Pathfinder, 227 
Mars-like soils, 211,216 
Martian meteorite, 4, 227, 230 
mass extinction, 245 
mass spectrometer, 183, 229, 278, 280 
master equation, 192, 194, 196, 198 

mechanism, 15, 61, 75, 76, 79-81, 83, 86, 95, 
98, 99, 103, 116, 122-125, 133, 152, 162, 
179, 228, 263, 293, 296, 350, 355 
mechanistic convergence, 136 
membranes, 46, 83, 86, 120, 210, 272 
mercaptans, 257-259 
mercaptans, non-living sources of, 259 
mesobiotic. 111, 114, 295 
metabolic pathways, 94, 104, 129-131, 263, 343 
metal sulfides, 15, 161, 164 
metallicity threshold, 168 
meteor spectroscopy, 201, 204 
meteorite bombardments, 66, 140 
meteorites, 15, 26, 55, 86, 121, 122, 136, 141, 
149, 150, 152, 181, 191, 194, 209, 227, 
230, 245-247, 262, 296, 328-330, 358, 


meteoroids, 178, 201-204 
methane, 5, 10-12, 64, 65, 95, 229, 255-257, 
276, 277, 282, 283, 287, 291, 295, 296 
methane hydrates, 277 
methanogen, 257, 258, 260, 263, 277, 296 
micelle. 111 

microbial mats, 242, 243 
microfossils, 3, 63, 66, 221, 222, 239, 240, 242, 
243, 247, 248, 250 

microorganisms, 129, 131, 139-142, 207-210, 
213-215, 221, 240-242, 248, 256, 259, 
260, 295, 296, 329 
microsope, 3, 229, 240, 270, 271 
Midcourse Space Experiment (MSX), 174-176 
Milky Way, 19, 171, 173-176, 299 
Miller, 3-5, 7, 9-16, 27, 28, 39, 49, 86, 87, 103, 
106, 107, no, 119, 120, 129, 132, 145, 
148, 157, 160, 186, 212, 216, 271, 272, 
281, 284, 285, 287, 358, 359, 362, 363 
mineral pyrite, 157 

mineral surfaces, 65, 103, 145, 148, 149, 151, 
152, 162, 163 
miniaturization, 270 

Minimal Unit of Terraforming (MUT), 233-236 

mole, 188, 213, 214, 228, 259 

molecular divergence, 136 

molecular evolution, 7, 109, 124, 132, 133, 159 

molecular hydrogen, 10, 62, 171, 172, 295 

molecular probes, 210, 269 

molecular structures, 45, 111, 265, 269 


molecular subtyping, 270 
Monera, 349, 35 1 
monocarboxylic acids, 213 
montmorillonite, 94, 146-149, 151, 152, 156, 

Moon, 203, 204, 256, 303-306, 311, 327 
Mbssbauer spectrometer, 220, 229-23 1 
Multiple Sequences Alignment (MSA), 133, 134 
Murchison meteorite, 14-16, 23, 86, 122, 195, 
209, 246, 248, 328, 330 

nanofossils, 141, 322 

NASA, 4, 5, 15, 27, 67-69, 141, 216, 275, 276, 
279, 284, 300, 320, 322 
NASA Astrobiology Institute, 27, 68, 69 
Natural Laws, 343, 350, 357, 358 
natural selection, 86, 132, 135, 137, 145, 312, 
323,328, 330, 345,350, 351 
nearest pair-wise interactions, 123 
Nearside, 303, 305 
Neoproterozoic, 247-250 
nervous system, 100, 312, 313, 330, 333 
networking activities, 67, 68 
neutral gas density, 288 
nicotinamides, 115-118 
Nintoku Seamounts, 218, 219 
nitrates, 214, 215 
nitriles, 277, 283, 287 

nitrogen, 5, 11, 14, 56-58, 118, 130-132, 154, 
170-172, 183, 213, 218, 236, 241, 254, 
275, 282, 283, 287-291, 293, 294, 296 
nitrogen fixation, 130, 132, 218 
NMR, 79, 82, 149, 150, 152, 271, 272, 282, 


non-equilibrium, 41, 83, 86 
non-equilibrium fluxes, 83, 86 
non-equilibrium process, 86 
non-habitable planets, 168 
nonlinear dynamics, 73 
non-living sources of mercaptans, 249 
nucleic acid-clay complexes, 146, 147 
nucleotides, 47, 91, 97, 103, 105, 111, 112, 
115-117, 119, 120, 145, 153-156, 

161-164, 184, 186, 328, 360 

O’Neill, J„ 303 

Ocean Drilling Program (ODP), 217-220 

Odyssey, 4, 227, 322 
oldest intelligent civilization, 172 
oligomerization, 113, 114, 123, 124, 153, 156 
oligomers, 103, 113, 120, 121, 123, 146, 148, 
156, 278, 355 

Oparin-Haldane hypothesis, 129 
operon duplication, 130, 132 
Opportunity, 4, 138 

organic carhon, 23, 26, 218, 220, 222, 227, 

organic compounds, 4, 9, 10, 12-16, 93, 103, 
129, 130, 136, 141, 146, 183, 190, 201, 

213, 246, 247, 277, 281, 285, 295, 296, 


organic molecules, 11, 15, 23, 26, 94, 103, 111, 
116, 125, 126, 146, 151, 170, 171, 183, 
185, 187, 190, 191, 195, 196, 204, 213, 

organics, 179, 190, 212, 213, 217-220, 227, 

258, 275, 277, 278, 322 

origins of life, 3, 48, 67, 81, 114, 124, 126, 128, 
145, 160, 185, 186, 204, 246, 248, 355, 


origins of living heings, 311, 314, 331, 

341-344, 355 
Origins program, 320 
oxidants, 211, 212, 215, 217, 227 
oxirane, 277, 280 

pairwise alignment, 133 

palaeobiological, 245, 247, 249 

palaeobiology, 249, 250 

paleosoil, 217, 220 

palindromic, 89 

patchwork hypothesis, 130, 131 

pattern, 27, 32, 38, 41, 97-99, 108, 235, 301 

pentapeptide, 134 

peptide hond formation, 83, 86, 104 
peptide nucleic acid PNA, 183-186 
peptides, 85-87, 105, 111, 117, 121-123, 133, 
134, 183, 278, 360 

Permo-Triassic boundary, 245, 246, 248 
peroxonitrite, 215 

pH, 9, 85, 94, 126, 140, 141, 153-155, 158, 160, 

214, 215, 221, 222, 262 
Phased Array, 304 
phenotypical, 235 


philosophers, 341, 347, 363 
philosophy, 67, 68, 308, 342, 344, 345, 347, 
349, 350, 352, 360 

phosphate, 107-110, 116, 120, 123, 134, 147, 
148, 153, 155, 157-160, 163, 164 
phosphoryl transfer reactions, 161, 163 
photoexcitation, 115 

photosynthesis, 12, 16, 133, 136, 230, 233, 234, 

PHYLIP, 133 

phylogenetic tree, 133, 134, 208 
physical universe, 319-321, 323, 325 
Pico de Orizaba, treeline of, 223, 224 
piezophiles, 141 

planet formation, 4, 167, 168, 170, 171 
planetary system environment, 178, 179 
planetesimal accretion, 170, 171 
planetesimal formation, 167, 168 
planetesimals, 167, 168, 256 
planetary response drivers, 178, 179 
plurality of worlds, 326, 346, 348 
polymerases, 105, 106 

polymerization, 14, 83-86, 94, 103-105, 117, 
119, 120, 123, 124, 145, 146, 148, 149, 
153, 162, 272 

polymerization of amino acids, 83, 120, 123, 

polymerization reaction, 84, 85, 94, 103 
polymers, 73, 86, 87, 104, 109, 111, 113, 
118-120, 124, 145-148, 155, 187-190 
polyoxymethylene, 187, 190 
polyynes, 279 
population dynamics, 112 
Post Detection Protocols, 307-309 
postbiological universe, 319-321, 323-326 
power laws, 35-37, 40, 41, 49, 50 
pragmatic information, 98 
Pre Cambrian, 249, 353 
prebiological evolution, 14 
prebiotic, 9-16, 23, 26, 33, 46, 68, 73, 76, 83, 
93,94, 96, 103, 104, 107, 111, 114, 115, 
119, 123, 124, 129, 130, 145-149, 
152-156, 160, 164, 185, 221, 275, 
277-279, 282, 287, 293, 296, 355, 362 
prebiotic chemistry, 12, 14, 33, 46, 68, 93, 115, 
148, 277, 278, 362 
prebiotic soup, 15 

primitive Earth, 10, 11, 13-16, 94, 104, 106, 
110, 117, 119, 120, 132, 160, 204, 284, 

primordial chemistry, 59 

primordial conditions, 103, 164 

Principle of Constructive Continuity, 109, 110 

prokaryotes, 129, 132, 140, 142, 240, 241, 


proteinoid theory, 357 
proteinoids, 119, 357 

proteins, 11, 12, 39, 73, 83, 90, 941, 104, 105, 
107, 109, 115, 117, 119, 120, 124, 127, 
128, 131-133, 136, 137, 148, 179, 180, 
183-185, 254, 257, 270, 271, 350, 357, 
359, 360 

protein-stabilisation, 89, 91 
proton, 56, 80, 83-86, 107, 116, 152, 227, 231, 
258, 282 

proton flux, 85, 86 
proton nuclear magnetic resonance 
spectroscopy, 282 
proton-pumping PPi synthase, 107 
proto-planetary disks, life-time of, 167, 168 
pseudofossils, 221, 222 
psychrophiles, 140 
pterins, 115-118 
punctuation, 89-91 
pupose, 98, 100 

purine, 15, 116, 117, 119, 149, 153, 155,278 
pyrimidine, 15, 77, 103, 119, 147, 149, 153, 
155, 278, 356 

pyrite, 125, 126, 157-164, 295 
pyrolisis-gas chromatograpy-mass 
spectrometry, 211 
Pyrolohus fumarii, 140, 142 

quasar absorption-line systems, 167, 169, 171 

Radar, 202, 277, 278, 280, 294 

radiation field, 171, 263 

radiation sensor, 229 

radio astronomy, 303 

radio signals, 299-301, 303, 363 

radio signals, search for, from outer space, 299 

radioactive decay, 94 

radiotelescope, 299-301, 303 

rare-Earth hypothesis, 327 


rate equations, 192, 196 
rate of star formation, 21, 22, 26 
reactor’s chemistry, 282, 287-290 
redshift, 17, 19, 20-22, 26, 60, 61, 168, 169, 
171, 172 

reduced electric field, 288-290 
refractory organics, 190, 213, 279 
replication, 29, 46, 75, 76, 94, 103, 1 1 1, 1 14, 

1 15, 1 18, 123, 145, 148, 266, 272, 


revolutionary consequences, 347 
Rhodospirillum ruhrum, 108, 110, 133, 134 
ribonucleotide, 105, 109, 110, 115, 116, 

ribozymes, 104, 106, 115, 117, 118, 148, 


ribulose-1, 5-biphosphate carboxylase/ 
oxygenase (RuBisCo), 133, 134 
RNA, 27, 89, 91, 104-106, 109-111, 114-118, 
120, 145-148, 152, 156, 179, 184, 186, 
254, 270, 272, 273, 334, 360 
RNA world, 104, 106, 109, 111, 115, 117, 118, 
120, 146, 148, 152, 156, 179, 334 
RNA-binding, 89, 105 
RNA-binding motifs, 105 
Rosetta, 4, 183 
Rosetta-Lander, 183 
RuBisCo large chains, 133, 134 
runaway greenhouse, 254, 255, 321 

Soai-type reaction, 76 
Salam hypothesis, 79, 81 
salt mines, 141, 207-209 
scale invariance, 38, 40, 49, 50 
search for life, 66-69, 139, 176, 186, 210, 220, 
231, 244, 253, 256, 265, 266, 270 
search of life elsewhere, 134, 139, 256 
second-order phase transition, 79, 80 
sedimentation times, 167, 168 
self-organization, 29, 32, 33, 40, 48, 49, 87, 

111, 149, 358 
self-referential, 79, 89-91 
semiregular variables, 176 
sequence convergence, 135-137 
serpentinization, 263, 264 
SETI, 3, 299, 302, 303, 305-309, 320, 322, 323, 
325, 326, 337, 347, 348 

SETI Institute, 211, 217, 337, 347, 348 
SETI program, 299, 302, 322 
Shapley, H„ 319, 320, 326 
signature of life, 67, 257, 266, 272, 330 
soil, 93, 141, 146, 148, 211-220, 223, 224, 227, 

solid surfaces, 93-96 
sorption/desorption, 158 
Space Climate, 177, 180 
Space Weather, 177, 178, 180 
species, 289, 290 

specroscopy, 169, 189, 190, 194, 199, 201, 204, 
220, 246, 255, 280, 282, 354 
spontaneous generation, 76, 183, 328, 

SSP, 279 

standard candle, 20 
Stapledon, O., 323 

star formation, 21, 22, 26, 47, 57, 61, 184, 186, 
191, 198, 199, 321 
Stardust, 4 
stars, 299 

stationary state, 84, 85, 112, 114 
stellar astrophysics, 180, 303 
stellar space meteorology, 177-180 
stepped combustion, 229 
Stone artificial meteorite experiments, 185 
storms, 201-203 
stromatolites, 240, 246-250 
structural convergence, 136 
sub-basement fossil soils, 217, 218, 220 
sulfide minerals (chalcogenides), 125, 163 
sulfocyanic theory, 9, 353, 356 
sulphohes, 353 
SUPCRT92, 261 
superoxides, 212, 215 
surface-mediated origin of life, 146 
synchrotron, 149, 152, 184 
synthetases, 89-91 

telecommunication satellites, 304 
temperature, 9, 20, 56, 59, 79-84, 86, 98, 1 19, 
125, 126, 140-142, 152, 161, 183-185, 
188, 189, 192, 195, 198, 207, 212, 213, 
216, 221, 223, 224, 229, 230, 234, 235, 
253-255, 259, 262, 276, 278, 279, 282, 
287, 288, 293-296, 328, 354 


terminal longitude X, 304, 305 
terraforming, 233, 234, 237 
thermal gradients, treeline at, 223 
thermal proteins, 119, 120, 357 
thermodynamic, 86, 163, 173, 179, 234, 236, 
264, 294, 345 

tholins, 277, 279, 283, 284, 287, 288 
thrombolites, 240 

Titan, 4, 5, 68, 275-285, 287, 290, 291, 
293-296, 362 

Titan’s aerosols, 4, 276, 277, 281-283, 290 

Titan’s aerosol analogues, 280, 281, 283, 284 

Titan’s atmosphere, 4, 5, 281-284 

Titan’s chemistry, 281-284 

Titan’s interior, 286 

Titan’s putative ocean, 285 

traces of life, 69, 227, 228, 243 

Two Micron All Sky Survey (2MASS), 174-176 

ultraviolet (UV) radiation, 14, 115, 118, 140, 
141, 145, 147, 178, 187-189, 215, 217, 
229, 258, 259, 285, 288, 289 
ultraviolet sensor, 229 
universal Darwinism, 138, 329, 330 
Universe, evolution of, 17, 23, 27, 37, 39^1, 

47, 50, 59, 97 
UVIS, 278 

Venus, 10, 141, 142, 254-256, 276 
Viking, 213-216, 227, 275, 322 
Viking lander, 213, 215, 227 
VIMS, 278 
Voyagers, 276 

Warrawoona Formation, 65, 221 
Water, 4, 5, 10, 12, 23, 67, 80, 84-86, 94, 95, 
119, 139, 141, 142, 146, 150-154, 158, 
160, 162, 163, 179, 183, 184, 189, 209, 
211, 217, 219, 227, 234, 235, 237, 
240-244, 253-255, 257-260, 263, 265, 
269, 270, 276-278, 280, 293-296, 327, 
329, 343,350, 351,354, 357, 


water-ammonia ocean, 278 
wind gauge, 230 
worldviews, 319-323 

xerophiles, 141 
X-ray detector, 229 

young stellar objects (YSOs), 192 
Yungay area, 211-215 

Zechstein, 207, 209 

Zenithal Hourly Rates (ZHRs), 201-203 


Acharyya, K., 191, 195 
Akindahunsi, A. A., 135 
Alekseev, V. A., 125 
All, S. R., 153 
Amaral, M. R. D. Jr., 157 
Aretxaga, B. R., 345 

Bada, J.L., 9 
Bagaley, D. R., 211 
Bahn, P„ 119, 357 
Baltscheffsky, H„ 7, 107 
Baltscheffsky, M., 107 
Bar-Even, A., Ill 
Becerra, A., 103 
Benilan, Y„ 187, 287 
Bernard, J-M., 287 
Bhattacherjee, A. B., 257 
Biondi, E., 145 
Bogdanovskaya, V. A., 125 
Bonaccorsi, R., 217 
Bonapace, J. A. R, 157, 161 
Bortolotti, C., 299 
Brack, A., 67, 227 
Brim, M„ 129 
Broxterman, Q. B., 121 
Bubis, J., 83 
Buch, A., 211 
Buhse, T., 73 

Caceres, L., 211 

Capponi, F., 173 

Camerup, A. M., 221 

Cattani, A., 299 

Cemogora, G., 287 

Chadha, M. S., 361 

Chakrabarti, S., 191, 195 

Chakrabarti, S. K„ 191, 195 

Chela-Flores, J., 135, 257, 269, 327 

Chen, Y„ 79 

Chiappini, C., 55 

Ching-San, Y. A. Jr., 157 

Christy, A. G., 221 

Cipriani, R., 83 

Coll, P.,211,281,287 
Collis, W. J. M. R, 127 
Cosmovivi, C. B., 299 
Costa, C. S., 157 
Cottin, H., 187 
Coyne G. V., 17 
Crisma, M., 121 
Cruz-Kuri, L., 223 

D’Amico, N., 299 
De Amorim, D. S., 161 
De La Rosa, J., 211 
De Souza-Barros, R, 157, 161 
Delaye, L., 103 
Dick, S.J., 319 
Duarte, A. C. P, 157 

Rani, R., 129 
Rormaggio, R, 121 
Rranchi, M., 145 
Rraser, D., 149 
Rray, N., 187 

Galeotti, P, 307 
Gallardo, J., 173 
Gallori, E., 145 
Gatta, R. S., 265, 269 
Gazeau, M.-C., 187 
Genta, G., 307, 311 
Gomez- Silva, B., 211 
Gracia-Ruiz, J. M., 221 
Gruber, C., 207 
Grubbs, R., 119 
Grunthaner, R J., 21 1 
Guimaraes, R. C., 89 

Hollen, B. J., 211 
Hyde, S. T., 221 

Islas, S., 103 

Johnson, T. V., 3 
Jolly, A., 287 



Kamaluddin, 153 
Kamber, B. S., 63 
Kaptein, B., 121 
Kritsky, M„ 115, 125 
Kafri, R„ 1 1 1 

Lai, R, 79 
Lancet, D., Ill 
Larson, A-K., 221 
Lazcano, A., 9, 103, 353 
Lebreton, J-R, 275 
Legal, A., 207 
Leuko, S., 207 
Levigard, R. B., 157 
Lorca, J., 201 
Lyudnikova, T. A., 115 

Maccaferri, A., 299 
Maccone, C., 299, 303 
Mancinelli, R. L., 217 
Matteucci, R, 55 
Mckay, Ch. R, 211, 223 
Meierhenrich, U. J., 183 
Mercader, J. R, 27 
Messerotti, M., 177 
Micheau, J. C., 73 
Miller, S. L„ 9 
Minniti, D., 173 
Molina, R, 211 
Monari, J., 299 
Monte, M. B. M„ 157, 161 
Montebugnoli, S., 299 
Moorbath. S., 63 
Moreira, C. H. C., 89 
Moretto, A., 121 
Mosqueira. F. G., 93, 123 
Musso, R, 335 

Navarro-Gonzalez, R., 211, 223, 

Negron-Mendoza, A., 93, 123, 

Noventa, D., 307 

Orlati A., 299 
Oro, J„ 201 

Otroshchenko, V. A., 125 
Owen T„ 253, 275 

Rappelis A., 119, 357 
Rensado Diaz, H. O., 233 
Rerez-Castineira, J. R., 107 
Rerezgasga, L., 353 
Rersson, B., 107 
Rfaffernhuemer, M., 207 
Ricco, G., 307 
Rillinger, C. T„ 227 
Rintassilgo, C. D., 287 
Roloni, M., 299 
Rontes-Buarque, M., 161 
Roppi, S., 299 
Ruy, D., 59 

Quinn, R. C., 211 

Radax, C., 207 

Rainey, F. A., 211 

Ramirez, S. L, 281 

Ramos-Bernal, S., 93, 123 

Raulin, R, 187, 211, 275, 281, 287 

Raulin-Cerceau, R, 349 

Righini, S., 299 

Rivera-Islas, J., 73 

Roederer, J. G., 97 

Roma, M., 299 

Ryzhkov, Yu. R, 125 

Scharifker, B., 83 
Schultz, A., 107 
Seckbach, J., 139 
Serani-Merlo, A., 341 
Shah, T. K„ 333 
Shenhav, B„ 111 
Shil, R, 133 
Shock, E„ 261 
Silva, E„ 353 
Simakov, M. B., 293 
Sims, M. R„ 227 
Small, A. M„ 211 
Spohn, T„ 261 
Stan-Lotter, LI., 207 
Sternberg, R., 211 

Telegina, T. A., 115 
Teodorani, M., 299 
Tessis, A. C., 161 
Tewari, V. C., 245, 249 

Thomas, S., 133 

Vladilo, G., 167, 169 


Toniolo, C., 121 

Vladimirov, M. G., 125 

Trigo-Rodriguez, J. M., 201 
Valcarce, A., 173 

Wang Wenqing, 79 
Weidler, G., 207 

Vance, S., 261 

Westall, R, 239 

Velasco, A. M., 103 

Wieland, H„ 207 

Vicuna, R., 341 
Vidyasagar, R B., 133 

Yao, N„ 79 

Vieyra, A., 157, 161 
Vladar, H. P. De, 83 

Zemskova, Yu. L., 115