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SP-1231

SP-1231October 1999

Exobiology in the Solar System & The Search for Life on Mars

Exobiology in the Solar System & The Search for Life on MarsReport from the ESA Exobiology Team Study 1997-1998

SP-1231October 1999

EXOBIOLOGY IN THE SOLAR SYSTEM AND THE SEARCH FOR LIFE ON MARS

Report from the ESA Exobiology Team Study 1997-1998

Cover Fossil coccoid bacteria, 1 m in diameter, found in sediment 3.3-3.5 Gyr old from the Early Archean of South Africa. See pages 160-161. Background: a portion of the meandering canyons of the Nanedi Valles system viewed by Mars Global Surveyor. The valley is about 2.5 km wide; the scene covers 9.8 km by 27.9 km centred on 5.1N/48.26W. The valley floor at top right exhibits a 200 m-wide channel covered by dunes and debris. This channel suggests that the valley might have been carved by water flowing through the system over a long period, in a manner similar to rivers on Earth. (Malin Space Science Systems/NASA)

SP-1231 Exobiology in the Solar System and The Search for Life on Mars, ISBN 92-9092-520-5 Scientific Coordinators: Edited by: Published by: Price: Copyright: Andr Brack, Brian Fitton and Franois Raulin Andrew Wilson ESA Publications Division ESA Publications Division ESTEC, Noordwijk, The Netherlands 70 Dutch Guilders/ EUR32 1999 European Space Agency

Contents

Foreword I An Exobiological View of the Solar System

7 15 17 19 19 19 20 21 21 22 27 27 27 27 29 30 31 31 32 34 36 41 41 41 41 42 44 47 48 48 49 49 51 51 53 54 54 57

I.1 Introduction I.2 Chemical Evolution in the Solar System 2.1 Terrestrial Prebiotic Chemistry 2.1.1 Terrestrial Production of Reduced Organic Molecules 2.1.2 Extraterrestrial Delivery of Organic Molecules to the Earth 2.2 Chemical Evolution on Other Bodies of the Solar System 2.2.1 The Icy Bodies: Comets, Europa, Ganymede 2.2.2 The Non-Icy Bodies: Titan, Giant Planets, Venus, Moon, Mars I.3 Limits of Life under Extreme Conditions 3.1 Introduction 3.2 Extreme Temperature Regimes 3.2.1 High Temperatures 3.2.2 Low Temperatures 3.3 High-Salt Environments 3.4 Acidic and Alkaline Environments 3.5 High-Pressure Environments 3.6 Subterranean Life 3.7 Survival of Lifeforms in Space 3.8 Implications for Exobiology in Future Searches I.4 Morphological and Biochemical Signatures of Extraterrestrial Life: Utility of Terrestrial Analogues 4.1 Introduction 4.2 Evidence of Extant Life 4.2.1 The Microbial World 4.2.2 Structural Indications of Life 4.2.3 Evidence of Microbial Activity as a Functional Characteristic of Life 4.2.4 Chemical Signatures and Biomarkers 4.2.5 Indirect Fingerprints of Life 4.2.6 Conclusions 4.3 Evidence of Extinct (Fossil) Extraterrestrial Life 4.3.1 Paleontological Evidence 4.3.1.1 Microbialites 4.3.1.2 Cellular Microfossils 4.3.2 Biogeochemical Evidence 4.3.2.1 Sedimentary Organic Carbon as a Recorder of Former Life Processes 4.3.2.2 13C/12C in Sedimentary Organic Matter: Index of Autotrophic Carbon Fixation 4.3.2.3 Molecular Biomarkers (Chemical Fossils) in Sediments

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I.5 Potential Non-Martian Sites for Extraterrestrial Life 5.1 The Icy Satellites 5.1.1 Europa 5.1.2 Ganymede 5.1.3 Other Icy Satellites 5.2 Titan 5.2.1 The Titan Atmosphere 5.2.2 The Titan Surface 5.2.3 The Cassini/Huygens Mission I.6 Science and Experiment Strategy 6.1 Where to Search? 6.2 What to Search For? 6.3 What to Search With? I.7 Summary of the Science Team Recommendations 7.1 The Search for Extant and Extinct Life 7.2 The Study of the Precursors of Life 7.3 Organic Chemistry Processes and Microorganisms in Space 7.4 Laboratory-based Studies II The Search for Life on Mars

65 65 65 66 67 67 67 69 71 73 73 75 76 77 77 77 78 78 79 81 83 83 84 85 87 88 89 90 91 92 92 93

II.1 Introduction II.2 The Planet Mars 2.1 The Geology of Mars 2.2 Volcanism and Tectonism 2.3 The Bulk Chemical Composition of Mars 2.4 The Geochemistry of the Martian Surface Layers 2.5 Water and Ground Ice 2.6 The Climate of Mars 2.7 NASA-Proposed Sites for Mars Exploration 2.7.1 Water and a Favourable Environment 2.7.2 Explorations for Extinct Life 2.7.3 Exploration for Extant Life 2.7.4 NASA Priority Landing Sites for Exobiology

II.3 The Martian Meteorites 95 3.1 Introduction 95 3.2 The Origin of SNC Meteorites 96 3.3 The Martian Meteorites 97 3.4 Exobiology and the Martian Meteorites 98 3.5 Carbon Compounds in Other Meteorites (Carbonaceous Chondrites) 101 3.6 Carbon Compounds in Micrometeorites 103 II.4 Team I: Exobiology and the Mars Surface Environment 4.1 Environments and Rocks with Exobiology Potential 4.1.1 Lacustrine Environments 4.1.2 Sebkha Environments 4.1.3 Thermal-Spring Deposits 4.1.4 Duricrusts 4.1.5 Glacial Deposits 4 109 109 109 110 113 113 113

4.2 4.3 4.4

4.5 4.6 4.7

4.1.6 Polar Deposits 4.1.7 Ground Ice-Permafrost General Remarks on Subsurface Microbial Fossils Climatic and Environmental Models The Radiation Environment 4.4.1 The Current Atmospheric Radiation Budget 4.4.2 The Current Particle and Radiation Environment 4.4.3 The Radiation Environment in the Past The Rationale for Landing Site Selection Rovers and Drilling Operations Landing Sites

114 114 115 115 117 118 119 119 120 122 122 129 129 130 130 132 132 132 133 133 133 133 135 135 135 135 138 138 140 142 142 144 145 147 147 148 148 148 149 150 150 151 151 152 153 157 157 5

II.5 Team II: The Search for Chemical Indicators of Life Scientific Objectives: 5.1 Sample Acquisition and Distribution Subsystem 5.2 Mineralogy, Petrology and Geochemistry 5.2.1 Mineralogy and Petrology 5.2.2 Geochemistry (Elemental Composition Analysis) 5.3 Isotopic Analysis 5.3.1 Carbon and Hydrogen 5.3.2 Sulphur 5.4 Molecular Analysis 5.4.1 Inorganics 5.4.2 Organics 5.5 The Search for Homochirality Instrumentation to Satisfy the Scientific Objectives: 5.6 Sample Acquisition and Distribution Subsystem 5.7 Mineralogy, Petrology and Geochemistry 5.7.1 General Considerations 5.7.2 Optical Microscopy 5.7.3 Alpha-Proton-X-ray Spectrometer (APX) 5.7.4 Mssbauer Spectrometer 5.7.5 Ion/Electron Probes, X-ray Spectroscopy 5.7.6 IR Spectroscopy 5.7.7 Raman Spectroscopy 5.8 Isotopic Analysis 5.9 Molecular Analysis 5.9.1 Gas Chromatography (GC) 5.9.2 Mass Spectroscopy (MS) 5.9.3 Pyrolysis (PYR) 5.9.4 Available PYR-GC-MS Techniques 5.9.5 Laser Ablation-Inductive Coupled Plasma-MS (LA-ICP-MS) 5.9.6 Other Techniques 5.9.7 The Analysis of H2O2 5.10 Chirality Measurements 5.10.1 Bulk Chirality Measurements 5.10.2 Enantiomeric Separations Recommended Payload and Technology Research Programme: II.6 Team III: The Inspection of Subsurface Aliquots and Surface Rocks Scientific Justification: 6.1 The Investigation of Unweathered Rock Material

6.2 6.3 6.4 6.5 6.6 6.7

Imaging of Fossilised Material in Sediments 6.2.1 Macroscopic Scale 6.2.2 Microscopic Scale Investigation of Biominerals Investigation of the Rock Structure 6.4.1 Extinct Microbes in Rock 6.4.2 Rock Formation and Composition Investigation of Sedimentary Layering Investigation of the Soil Investigation of Dust Particles

157 158 160 161 163 163 164 165 165 166 167 168 170 170 170 171 171 171 172 173 173 174 174 174 174 175 175 179 179 180 180 180 181 181 181 184

Scientific Method and Requirements: 6.8 Initial Survey and Target Selection 6.9 High-Resolution Studies 6.10 Subsurface Investigations 6.11 Raman Spectrometry 6.12 Optical Spectroscopy 6.13 Mssbauer Spectroscopy 6.14 IR Spectroscopy 6.15 Thermal-IR Spectroscopy 6.16 Chemical Inspection of Subsurface Material 6.17 Summary of Possible Instrumentation Sampling Aspects: 6.18 Mobility Requirements 6.19 Grinding/Polishing/Immersion 6.20 Drilling and Digging 6.21 Sieving and Magnetic Separation 6.22 Cutting and Sawing 6.23 Data Analysis 6.24 Summary of Major Conclusions II.7 Conclusions 7.1 Landing Sites for Exobiology 7.2 The Sample Acquisition, Distribution and Preparation System 7.2.1 Subsurface Sample: Acquisition and Preparation 7.2.2 Surface Rock Sample: Acquisition and Preparation 7.2.3 Soil Samples 7.3 The Exobiology Observation System 7.4 The Exobiology Analysis System 7.5 A Possible Exobiology Experiment Package and Operating Arrangement Annex 1: Team IV. A Manned Mars Station and Exobiology Research

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FOREWORD

The Exobiology Science Team was established in September 1996 by Dr. P. Clancy of ESAs Directorate of Manned Spaceflight and Microgravity. The task of the Team was to survey current research in exobiology and related fields and then to make recommendations to ESA on the nature of a future search for life elsewhere in the Solar System. In carrying out that task, the Team has benefited considerably from the contributions provided by many other experts, as listed below. From a scientific point of view, it is probably the first time in recent years that the various relevant aspects involved in a potential search for life elsewhere have been brought together and examined in such detail in Europe. Likewise, this is the first attempt to outline what exobiology space experiments might reasonably be planned, given the limited resources currently available in Europe for new ventures, however exciting they may be. The results of this first study are presented in Part I. For this part, the Team comprised: Chairman: Andr Brack, Centre de Biophysique Molculaire, CNRS, Orlans, France. Patrick Forterre, Institut de Gntique et Microbiologie, Universit de Paris Sud, Orsay, France. Gerda Horneck, Institute of Aerospace Medicine, DLR, Porz-Wahn, Germany. Colin Pillinger, Planetary Sciences Research Institute, Open University, Milton Keynes, UK. Manfred Schidlowski, Max-Planck Institut fr Chemie, Abteilung Biochemie, Mainz, Germany. Heinrich Wnke, Max-Planck Institut fr Chemie, Abteilung Kosmochemie, Mainz, Germany. Secretary: Brian Fitton, European Science Consultants, Sassenheim, Netherlands. With the folowing c