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

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Contents Foreword 7 I An Exobiological View of <strong>the</strong> <strong>Solar</strong> <strong>System</strong> 15 I.1 Introduction 17 I.2 Chemical Evolution <strong>in</strong> <strong>the</strong> <strong>Solar</strong> <strong>System</strong> 19 2.1 Terrestrial Prebiotic Chemistry 19 2.1.1 Terrestrial Production of Reduced Organic Molecules 19 2.1.2 Extraterrestrial Delivery of Organic Molecules to <strong>the</strong> Earth 20 2.2 Chemical Evolution on O<strong>the</strong>r Bodies of <strong>the</strong> <strong>Solar</strong> <strong>System</strong> 21 2.2.1 <strong>The</strong> Icy Bodies: Comets, Europa, Ganymede 21 2.2.2 <strong>The</strong> Non-Icy Bodies: Titan, Giant Planets, Venus, 22 Moon, Mars I.3 Limits of <strong>Life</strong> under Extreme Conditions 27 3.1 Introduction 27 3.2 Extreme Temperature Regimes 27 3.2.1 High Temperatures 27 3.2.2 Low Temperatures 29 3.3 High-Salt Environments 30 3.4 Acidic and Alkal<strong>in</strong>e Environments 31 3.5 High-Pressure Environments 31 3.6 Subterranean <strong>Life</strong> 32 3.7 Survival of <strong>Life</strong><strong>for</strong>ms <strong>in</strong> Space 34 3.8 Implications <strong>for</strong> <strong>Exobiology</strong> <strong>in</strong> Future <strong>Search</strong>es 36 I.4 Morphological and Biochemical Signatures of Extraterrestrial <strong>Life</strong>: 41 Utility of Terrestrial Analogues 4.1 Introduction 41 4.2 Evidence of Extant <strong>Life</strong> 41 4.2.1 <strong>The</strong> Microbial World 41 4.2.2 Structural Indications of <strong>Life</strong> 42 4.2.3 Evidence of Microbial Activity as a Functional 44 Characteristic of <strong>Life</strong> 4.2.4 Chemical Signatures and Biomarkers 47 4.2.5 Indirect F<strong>in</strong>gerpr<strong>in</strong>ts of <strong>Life</strong> 48 4.2.6 Conclusions 48 4.3 Evidence of Ext<strong>in</strong>ct (Fossil) Extraterrestrial <strong>Life</strong> 49 4.3.1 Paleontological Evidence 49 4.3.1.1 Microbialites 51 4.3.1.2 Cellular Microfossils 51 4.3.2 Biogeochemical Evidence 53 4.3.2.1 Sedimentary Organic Carbon as a Recorder 54 of Former <strong>Life</strong> Processes 4.3.2.2 13 C/ 12 C <strong>in</strong> Sedimentary Organic Matter: 54 Index of Autotrophic Carbon Fixation 4.3.2.3 Molecular Biomarkers (‘Chemical Fossils’) 57 <strong>in</strong> Sediments 3
4 I.5 Potential Non-Martian Sites <strong>for</strong> Extraterrestrial <strong>Life</strong> 65 5.1 <strong>The</strong> Icy Satellites 65 5.1.1 Europa 65 5.1.2 Ganymede 66 5.1.3 O<strong>the</strong>r Icy Satellites 67 5.2 Titan 67 5.2.1 <strong>The</strong> Titan Atmosphere 67 5.2.2 <strong>The</strong> Titan Surface 69 5.2.3 <strong>The</strong> Cass<strong>in</strong>i/Huygens Mission 71 I.6 Science and Experiment Strategy 73 6.1 Where to <strong>Search</strong>? 73 6.2 What to <strong>Search</strong> For? 75 6.3 What to <strong>Search</strong> With? 76 I.7 Summary of <strong>the</strong> Science Team Recommendations 77 7.1 <strong>The</strong> <strong>Search</strong> <strong>for</strong> Extant and Ext<strong>in</strong>ct <strong>Life</strong> 77 7.2 <strong>The</strong> Study of <strong>the</strong> Precursors of <strong>Life</strong> 77 7.3 Organic Chemistry Processes and Microorganisms <strong>in</strong> Space 78 7.4 Laboratory-based Studies 78 II <strong>The</strong> <strong>Search</strong> <strong>for</strong> <strong>Life</strong> on Mars 79 II.1 Introduction 81 II.2 <strong>The</strong> Planet Mars 83 2.1 <strong>The</strong> Geology of Mars 83 2.2 Volcanism and Tectonism 84 2.3 <strong>The</strong> Bulk Chemical Composition of Mars 85 2.4 <strong>The</strong> Geochemistry of <strong>the</strong> Martian Surface Layers 87 2.5 Water and Ground Ice 88 2.6 <strong>The</strong> Climate of Mars 89 2.7 NASA-Proposed Sites <strong>for</strong> Mars Exploration 90 2.7.1 Water and a Favourable Environment 91 2.7.2 Explorations <strong>for</strong> Ext<strong>in</strong>ct <strong>Life</strong> 92 2.7.3 Exploration <strong>for</strong> Extant <strong>Life</strong> 92 2.7.4 NASA Priority Land<strong>in</strong>g Sites <strong>for</strong> <strong>Exobiology</strong> 93 II.3 <strong>The</strong> Martian Meteorites 95 3.1 Introduction 95 3.2 <strong>The</strong> Orig<strong>in</strong> of SNC Meteorites 96 3.3 <strong>The</strong> Martian Meteorites 97 3.4 <strong>Exobiology</strong> and <strong>the</strong> Martian Meteorites 98 3.5 Carbon Compounds <strong>in</strong> O<strong>the</strong>r Meteorites (Carbonaceous Chondrites) 101 3.6 Carbon Compounds <strong>in</strong> Micrometeorites 103 II.4 Team I: <strong>Exobiology</strong> and <strong>the</strong> Mars Surface Environment 109 4.1 Environments and Rocks with <strong>Exobiology</strong> Potential 109 4.1.1 Lacustr<strong>in</strong>e Environments 109 4.1.2 Sebkha Environments 110 4.1.3 <strong>The</strong>rmal-Spr<strong>in</strong>g Deposits 113 4.1.4 Duricrusts 113 4.1.5 Glacial Deposits 113
Page 1 and 2: SP-1231 Exobiology
Page 3: Cover Fossil coccoid bacteria, 1 µ
Page 7 and 8: 6 6.2 Imaging of F
Page 9 and 10: The Exobio
Page 11 and 12: pyrolysis, or similar techniques, f
Page 13 and 14: Ignasi Casanova, Institute
Page 15 and 16: I AN EXOBIOLOGICAL VIEW OF THE SOLA
Page 17 and 18: SP-1231 18 surface pressure of CO 2
Page 19 and 20: SP-1231 20 10 bar befor</st
Page 21 and 22: SP-1231 22 kilometres in</s
Page 23 and 24: SP-1231 24 Laboratory Investigation
Page 25 and 26: I.3 Limits of Life
Page 27 and 28: temperatures of 95-106ºC. This sug
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Page 31 and 32: cannot exclude fin
Page 33 and 34: Responses to Cosmic Radiation <stro
Page 35 and 36: acid to identify the</stron
Page 37 and 38: Horneck, G. (1993). Responses of Ba
Page 39 and 40: SP-1231 Fig. I.4.2.2/1. Size distri
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Page 43 and 44: SP-1231 Fig. I.4.2.3/1A (left). Net
Page 45 and 46: SP-1231 48 A detailed chemical anal
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Page 49 and 50: SP-1231 Fig. I.4.3.1.2/1. A: Compar
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SP-1231 Fig. I.4.3.2.3/1. Cholester
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SP-1231 60 References regard to non
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SP-1231 62 Klein,
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SP-1231 64 ities in</strong
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SP-1231 Fig. I.5.1.1/1. A 34×42 km
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SP-1231 Fig. I.5.2.1/1. Titan’s a
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SP-1231 Fig. I.5.2.2/2. Modelled Ti
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SP-1231 72 Galileo: images availabl
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SP-1231 74 TABLE I.6.2/1 EVIDENCE O
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SP-1231 I.6.3 What to Searc
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SP-1231 78 I.7.3 Organic Chemistry
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II.1 Introduction The</stro
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II.2 The Planet Ma
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cover the range 4.
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The depletion of c
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valley networks (Fig. II.2.5/2) are
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plate tectonic evidence has been ob
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Table II.2.7.4/1. Potential Mars <s
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II.3 The Martian M
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principal atmosphe
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Lines of evidence
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indicated by carbo
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quest for
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Anders, E. (1989). Prebiotic organi
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Urey, H.C. (1968). Origin</
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SP-1231 Fig. II.4.1.1/1. A Gilbert-
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SP-1231 Fig. II.4.1.3/1. Th
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SP-1231 114 Sinuou
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SP-1231 Fig. II.4.3/1. Ages of seve
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SP-1231 118 orbital characteristics
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SP-1231 120 II.4.5 The</str
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SP-1231 122 II.4.6 Rovers and Drill
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SP-1231 124 Site 2: Apolin<
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SP-1231 126 Site 4: Chasma area, ea
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SP-1231 128 Sharp, M., Parkes, J.,
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SP-1231 Fig. II.5.1/1. The<
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SP-1231 132 II.5.3 Isotopic Analysi
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SP-1231 134 chemical composition de
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SP-1231 Fig. II.5.7.1/1. Th
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SP-1231 138 optical microscope. Bot
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SP-1231 140 protons of discrete ene
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SP-1231 142 atures should be per<st
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SP-1231 Fig. II.5.7.7/1. Example of
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SP-1231 146 soils. In this approach
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SP-1231 148 discrimin</stro
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SP-1231 150 determin</stron
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SP-1231 Fig. II.5.10.2/2. Enantiome
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SP-1231 154 References achiral colu
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II.6 Team III: The
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in width and heigh
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Searchin</
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minerals or oxidat
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A second group of rocks, however, m
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SCIENTIFIC METHOD AND REQUIREMENTS
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The sample materia
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surprising. To ach
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The main</
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Consideration of a diamond wire-saw
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Schoonen, M.A. & Barnes, H.L. (1991
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SP-1231 180 II.7.2 The</str
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SP-1231 Fig. II.7.4/1. Look
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SP-1231 184 II.7.5 A Possible <stro
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Team IV was asked to examin
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