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

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SP-1231 170 II.6.10 Subsurface Investigations II.6.11 Raman Spectroscopy II.6.12 Optical Spectroscopy mission with a mass of
surpris<strong>in</strong>g. To achieve more than Pathf<strong>in</strong>der, an optical spectrograph must have an extremely high signal-to-noise and even <strong>in</strong> this case it is arguable whe<strong>the</strong>r an unambigious identification of a m<strong>in</strong>eral could be made. O<strong>the</strong>r techniques (such as Mössbauer spectroscopy) should be <strong>in</strong>vestigated. Mössbauer spectroscopy can provide a clear <strong>in</strong>dication of <strong>the</strong> composition of iron compounds and FE-bear<strong>in</strong>g m<strong>in</strong>erals. It is discussed fur<strong>the</strong>r with<strong>in</strong> <strong>the</strong> Team II report <strong>in</strong> Section II.5.7.4. II.6.14.1 Objectives IR spectroscopy <strong>in</strong> <strong>the</strong> range 0.8-4.0 µm can be used to determ<strong>in</strong>e <strong>the</strong> abundances of many types of m<strong>in</strong>erals, <strong>in</strong>clud<strong>in</strong>g clays, hydrates and carbonates. Carbonate materials (such as magnesite, calcite and siderite) can easily be dist<strong>in</strong>guished from - one ano<strong>the</strong>r. All have near-IR features <strong>in</strong> <strong>the</strong> 1.7-2.5 µm range attributable to <strong>the</strong> CO3 anion. Sulphates such as gypsum and anhydrite, have absorptions <strong>in</strong> <strong>the</strong> 1.0-1.5 µm and 4.0-4.7 µm ranges. Ferrous absorptions of pyroxenes are also evident <strong>in</strong> <strong>the</strong> 1.0- 2.0 µm region. <strong>The</strong> ratio of <strong>the</strong> 1 µm to 2 µm absorptions is diagnostic of <strong>the</strong> composition. Although oliv<strong>in</strong>e has only been found <strong>in</strong> one martian meteorite, <strong>the</strong> structure of <strong>the</strong> broad absorption feature is also a diagnostic of composition. <strong>The</strong> absorptions of C-H and C-N bear<strong>in</strong>g organics can be found throughout <strong>the</strong> 1.7-4.0 µm range. A spectral resolution of >100 (λ/∆λ) would be sufficient. Good spatial resolution is needed to <strong>in</strong>vestigate variations with<strong>in</strong> a sample and we estimate that a resolution of 200 µm should be atta<strong>in</strong>able. A secondary objective <strong>for</strong> IR spectroscopy would be <strong>in</strong>vestigation of <strong>the</strong> atmosphere. CO 2, H 2O and CO all have characteristic absorption bands <strong>in</strong> <strong>the</strong> IR. <strong>The</strong> variations of <strong>the</strong>se gases toge<strong>the</strong>r with <strong>the</strong> dust cycle are strongly coupled <strong>in</strong> <strong>the</strong> martian atmosphere and hence this could provide significant additional <strong>in</strong><strong>for</strong>mation on <strong>the</strong> time variability of <strong>the</strong> atmosphere. Local sources of <strong>the</strong>se gases may be present, <strong>in</strong>dicat<strong>in</strong>g hydro<strong>the</strong>rmal activity. It should be noted that <strong>the</strong> highest resolution near-IR spectroscopic measurements of Mars come from <strong>the</strong> Hubble Space Telescope, at around 200 km px -1 . <strong>The</strong>se data show variations <strong>in</strong> ferric alteration m<strong>in</strong>erals and primary ferrous silicates but are limited by <strong>the</strong>ir coarse spatial resolution. It is not clear whe<strong>the</strong>r we will see low contrast <strong>in</strong> high spatial resolution data (as was seen <strong>in</strong> <strong>the</strong> optical with <strong>the</strong> Mars Pathf<strong>in</strong>der imager) or whe<strong>the</strong>r IR spectroscopy at <strong>the</strong> 200 µm level will be extremely reveal<strong>in</strong>g. II.6.14.2 Requirements Low-mass IR spectrometer systems have been proposed <strong>for</strong> several missions, <strong>in</strong>clud<strong>in</strong>g <strong>the</strong> RoLand lander on <strong>the</strong> Rosetta mission, and some systems are now commercially available. <strong>The</strong> system may require illum<strong>in</strong>ation devices (such as LEDs) <strong>in</strong> order to compensate <strong>for</strong> absorption l<strong>in</strong>es <strong>in</strong> <strong>the</strong> solar cont<strong>in</strong>uum at <strong>the</strong> surface caused by dust <strong>in</strong> <strong>the</strong> atmosphere. <strong>The</strong> system should, however, be comparable <strong>in</strong> mass and power consumption to <strong>the</strong> microscope. Because transmission IR spectroscopy may not be applicable (requir<strong>in</strong>g preparation of th<strong>in</strong> sections), <strong>the</strong> less diagnostic reflection mode may have to be selected. Even <strong>in</strong> this mode, however, identification of m<strong>in</strong>eral and organic compounds and detection of H 2O and (OH) <strong>in</strong> silicates should be relatively easy. On <strong>the</strong> o<strong>the</strong>r hand, a Raman microspectrometer should probably provide most of that <strong>in</strong><strong>for</strong>mation <strong>in</strong> a more unambiguous way. II.6.15.1 Objectives <strong>The</strong>rmal-IR spectroscopy <strong>in</strong> <strong>the</strong> 6-9.5 µm region can be used to <strong>in</strong>vestigate specific absorptions/emissions of carbon-bear<strong>in</strong>g molecules. Strong features are evident at 6.18 µm result<strong>in</strong>g from <strong>the</strong> C-C and C-O bonds, 6.86 µm (-CH2-, -CH3 scissor), team III: <strong>the</strong> <strong>in</strong>spection of subsurface aliquots and surface rocks/II.6 II.6.13 Mössbauer Spectroscopy II.6.14 IR Spectroscopy II.6.15 <strong>The</strong>rmal-IR Spectroscopy 171
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SP-1231 Exobiology
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Cover Fossil coccoid bacteria, 1 µ
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4 I.5 Potential Non-Martian Sites <
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6 6.2 Imaging of F
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The Exobio
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pyrolysis, or similar techniques, f
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Ignasi Casanova, Institute
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I AN EXOBIOLOGICAL VIEW OF THE SOLA
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SP-1231 18 surface pressure of CO 2
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SP-1231 20 10 bar befor</st
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SP-1231 22 kilometres in</s
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SP-1231 24 Laboratory Investigation
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I.3 Limits of Life
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temperatures of 95-106ºC. This sug
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(mainly found <str
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cannot exclude fin
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Responses to Cosmic Radiation <stro
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acid to identify the</stron
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Horneck, G. (1993). Responses of Ba
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SP-1231 Fig. I.4.2.2/1. Size distri
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SP-1231 Fig. I.4.2.2/4. Evaporite w
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SP-1231 Fig. I.4.2.3/1A (left). Net
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SP-1231 48 A detailed chemical anal
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SP-1231 Fig. I.4.3.1.1/1. Scheme of
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SP-1231 Fig. I.4.3.1.2/1. A: Compar
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SP-1231 54 I.4.3.2.1 Sedimentary Or
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SP-1231 56 The iso
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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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Page 161 and 162: SCIENTIFIC METHOD AND REQUIREMENTS
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Exobiology in the Solar System & The Search for Life on Mars - ESA

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