The Science of Astrobiology Cellular Origin, Life in Extreme Habitats and Astrobiology ________________________________________________________________ Volume 20 (Second Edition) ________________________________________________________________ Julian Chela-Flores The Science of Astrobiology A Personal View on Learning to Read the Book of Life Julian Chela-Flores The Abdus Salam International Centre for Theoretical Physics P.O. Box 586 34014 Trieste Italy [email protected] ISSN 1566-0400 ISBN 978-94-007-1626-1 e-ISBN 978-94-007-1627-8 DOI 10.1007/978-94-007-1627-8 Springer Dordrecht Heidelberg London New York Library of Congress Control Number: 2011934255 © Springer Science+Business Media B.V. 2011 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. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) The cupola in the West Atrium of St. Mark's Basilica in Venice, Italy representing the biblical interpretation of Genesis (Cf., also pp. 215-216 at the beginning of Part 4: The destiny of life in the universe. With kind permission of the Procuratoria of St. Mark's Basilica.) For Sarah Catherine Mary Table of contents Table of contents vii Preface xvii Acknowledgements xxi Recommendations to the readers xxiii INTRODUCTION The cultural and scientific context of astrobiology I.1 Early attempts to read the Book of Life 3 ARISTARCHUS OF SAMOS AND HIPPARCHUS 4 NICHOLAS OF CUSA (CUSANUS) 4 NICHOLAS COPERNICUS 4 GIORDANO BRUNO 5 CHARLES DARWIN 6 I.2 Some pioneers of the science of astrobiology 8 ALEXANDER OPARIN 8 STANLEY MILLER 10 SIDNEY W. FOX 11 CYRIL PONNAMPERUMA 12 JOHN ORO, 1ST MARQUESS OF ORÓ 13 I.3 Three strategies for astrobiological exploration 14 I.4 Inserting philosophy into astrobiology 17 I.5 Emphasizing the role of biology in astrobiology 17 I.6 Inserting physics in biology especially in astrobiology 18 I.7 Inserting the earth sciences in astrobiology 19 vii viii THE SCIENCE OF ASTROBIOLOGY I.8 New fingerprints of early life 23 I.9 Inserting paleontology into astrobiology 24 Supplementary Reading 26 References 27 THE BOOK OF LIFE PART 1: THE ORIGIN OF LIFE IN THE UNIVERSE CHAPTER 1. From cosmic to chemical evolution 1.1 Beginnings of a rational cosmology based on physical constraints 31 1.2 Cosmological models 32 1.3 The cosmic microwave background 34 1.4 The growth of studies on the origin of life 35 1.5 Origin of the elements: from the big bang to the interior of stars 37 1.6 Supernovae: the source of biogenic dust 39 1.7 Molecular clouds and circumstellar disks 42 1.8 Stellar and biological evolution 43 Supplementary Reading 45 References 46 CHAPTER 2. From chemical to prebiotic evolution 2.1 Organic Cosmochemistry 47 2.2 Precursor biomolecules in interplanetary dust 48 2.3 Cosmic dust and comets: their role in astrobiology 49 2.4 Origin of the Solar System: the Rosetta mission 51 2.5 Origin of the terrestrial planets 52 2.6 Origin of the Jovian planets 53 2.7 Origin of the moons in the outer Solar System 55 Supplementary Reading 55 References 56 TABLE OF CONTENTS ix CHAPTER 3. Sources of life’s origin: A search for biomarkers 3.1 The Moon and its water content as a mirror of the early Earth 57 3.2 Biogenic elements on asteroids 63 3.3 Biogenic elements on comets 64 3.4 Biogenic elements on meteorites 66 3.5 The Murchison meteorite 68 3.6 Biogenic elements in extreme terrestrial environments 70 3.7 A terrestrial analog to Europa in Antarctica: The dry valley lakes 72 3.8 A second terrestrial analog to Europa near the South Pole: Lake Vostok 75 3.9 A third terrestrial analog to Europa in the Canadian Arctic 76 Supplementary Reading 76 References 77 CHAPTER 4. From prebiotic evolution to the emergence of single cells 4.1 Which are the macromolecules of life? 79 4.2 The primitive Earth 80 4.3 The origin of the first cell 81 4.4 A biochemical relic of the earliest stages of life 82 4.5 Symmetry in the cosmos 83 4.6 Symmetry in the life sciences 85 ASYMMETRY IN THE ANIMAL WORLD 85 ASYMMETRY IN THE MICROSCOPIC WORLD: CHIRALITY 85 HOMOCHIRALITY AS A BIOMARKER OF LIFE 86 ABDUS SALAM’S VISION OF SYMMETRY IN NATURE 87 THE ORIGIN OF CHIRALITY AND THE MURCHISON METEORITE 88 4.7 An analogy with languages: the genetic code 89 4.8 The origin of cellular organelles 90 4.9 From chemical to cellular evolution 91 4.10 The influence of the ancient Sun on the early evolution of life 91 4.11 Eventual deeper insights into the origin of life from solar missions 93 x THE SCIENCE OF ASTROBIOLOGY Supplementary Reading 98 References 98 THE BOOK OF LIFE PART 2: EVOLUTION OF LIFE IN THE UNIVERSE CHAPTER 5. From the age of prokaryotes to the emergence of eukaryotes 5.1 Could prokaryotes have emerged on the early Earth 4,4 Gyr ago? 103 5.2 The dawn of unicellular organisms 104 5.3 An early emergence of life makes the Moon a major target for astrobiology 105 5.4 A unique event lost somewhere deep in the Archean 106 5.5 The evolution of the Earth’s atmosphere: The Great Oxidation Event 106 5.6 The role of oxygen and iron in eukaryogenesis 108 5.7 First appearance of metazoans in the Paleoproterozoic 109 5.8 The origin of chromosomes 110 5.9 The Molecular Clock hypothesis 111 5.10 A transition in the pathway towards intelligence 112 5.11 In which environments can extremophiles survive in our Solar System? 113 5.12 Mechanisms of evolution beyond natural selection 113 5.13 The adaptation of life to extreme environments 115 Supplementary Reading 116 References 116 CHAPTER 6. The evolution of intelligent behavior 6.1 Modern taxonomy emphasizes single-celled organisms 119 6.2 The phenomenon of the eukaryotic cell 120 6.3 The phenomenon of multicellularity 121 6.4 Evolution of the hominoids 122 6.5 Evolution of intelligent behavior in the hominids 124 6.6 Did external events contribute to the evolution of intelligence on Earth? 126 6.7 The pathway towards communication 127 TABLE OF CONTENTS xi 6.8 The emergence of language and music in modern humans 128 Supplementary Reading 129 References 130 THE BOOK OF LIFE PART 3: THE DISTRIBUTION OF LIFE IN THE UNIVERSE CHAPTER 7. On the possibility of biological evolution on Mars 7.1 What have we learnt from previous missions to Mars? 135 7.2 An Eden-like early Martian environment 136 7.3 The early Viking Missions 137 7.4 Mars Pathfinder and the Sojourner Rover 139 7.5 The Mars Global Surveyor 139 7.6 Mars Express 141 7.7 The Phoenix Mission 142 7.8 The question of the origin, evolution and distribution of Martian life 144 7.9 Mars Odyssey and the Exploration Rover Opportunity 146 7.10 Is methane a possible biomarker in the Martian atmosphere? 147 7.11 Testing for life on Mars on terrestrial analogs 148 7.12 Mars in the second and third decades of the 21st century 149 Supplementary Reading 149 References 150 CHAPTER 8. On the possibility of biological evolution on the moons of Jupiter 8.1 The discovery of Europa 151 8.2 The Galileo mission 154 8.3 Tentative inventory of organic elements in the Europan ocean 157 8.4 The habitability of Europa 159 8.5 What are the constraints on the putative Europan biotope? 159 xii THE SCIENCE OF ASTROBIOLOGY 8.6 Technological challenges for reading further into the Book of Life 160 THE ORIGINAL HYDROBOT-CRYOBOT 160 ADVANCED DESIGN FOR HYDROBOTS 162 PENETRATORS; SURFICIAL LANDERS FOR EUROPA 162 8.7 Returning to the Jovian System 164 8.8 Are there biosignatures revealing a second biology on Europa? 164 8.9 Sulfur patches and space weather in the neighborhood of Europa 166 Supplementary Reading 168 References 168 CHAPTER 9. On the possibility of biological evolution on the moons of Saturn 9.1 The discovery of Titan 171 9.2 The Voyagers: The first missions to Saturn and Titan 172 9.3 The Cassini-Huygens Mission 173 9.4 Titan and Enceladus 175 9.5 The atmosphere and hydrosphere of Titan 177 9.6 Titan’s surface 179 9.7 Is there a liquid ocean on Titan? 181 9.8 The plumes and habitability of Enceladus 182 9.9 An eventual return to Titan and Enceladus 183 9.10 The habitability of Titan 184 Supplementary Reading 185 References 185 CHAPTER 10. How different would life be elsewhere? 10.1 Possible degrees of evolution of life 187 10.2 The search for other solar systems 188 10.3 How are extrasolar planets found? 189 10.4 Which are likely habitable zones? 190 10.5 The multiplicity of exoplanets in our galactic neighborhood 191 TABLE OF CONTENTS xiii 10.6 What is a planet? 191 10.7 The CoRoT mission 193 10.8 The Kepler mission 193 10.9 The discovery of the first super-Earths in habitable zones 194 10.10 Exomoonology: the habitability of satellites around other stars 194 10.11 Potentially habitable worlds: planets like Earth 197 Supplementary Reading 199 References 199 CHAPTER 11. The search for the evolution of exointelligence in worlds around other stars 11.1 What is our place in the universe? 201 11.2 Intelligent behavior is intimately related with the need to communicate 202 11.3 The Drake Equation 202 11.4 Progress in instrumentation 206 11.5 SETI on the Moon 208 11.6 From the first neuron to brains 209 11.7 Beyond geocentricism 210 11.8 The Fermi Paradox 211 11.9 SETI: towards the future 212 Supplementary Reading 213 References 214 THE BOOK OF LIFE PART 4: THE DESTINY OF LIFE IN THE UNIVERSE CHAPTER 12.