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

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Measurements with <strong>the</strong> Mössbauer <strong>in</strong>strument will be done by plac<strong>in</strong>g it aga<strong>in</strong>st <strong>the</strong> sample. Physical contact is required <strong>in</strong> order to m<strong>in</strong>imise possible microphonic noise on <strong>the</strong> velocity-modulated energy of <strong>the</strong> emitted gamma-rays. <strong>The</strong> field of view is circular (diameter about 1.5-2 cm). <strong>The</strong> average <strong>in</strong><strong>for</strong>mation depth <strong>for</strong> Mössbauer data is of <strong>the</strong> order of 100-200 mm, assum<strong>in</strong>g basaltic rock composition. <strong>The</strong> thickness of dust layers as found on rocks dur<strong>in</strong>g <strong>the</strong> Vik<strong>in</strong>g and Pathf<strong>in</strong>der missions may exceed this. To get at least some <strong>in</strong><strong>for</strong>mation from a possible wea<strong>the</strong>r<strong>in</strong>g r<strong>in</strong>d and <strong>the</strong> host rock, <strong>the</strong> dust needs to be removed by appropriate devices. Measurements be<strong>for</strong>e and after dust removal should be per<strong>for</strong>med. <strong>The</strong> Mössbauer parameters are temperature-dependent. Especially <strong>for</strong> small particles exhibit<strong>in</strong>g superparamagnetic behaviour (e.g. nanophase Fe-oxides, which may be of biogenic orig<strong>in</strong>), <strong>the</strong> Mössbauer spectrum may change drastically with temperature. <strong>The</strong> observation of such changes will help <strong>in</strong> determ<strong>in</strong><strong>in</strong>g <strong>the</strong> nature of <strong>the</strong> iron-bear<strong>in</strong>g phases. <strong>The</strong>re<strong>for</strong>e, Mössbauer measurements at different temper- team II: <strong>the</strong> search <strong>for</strong> chemical <strong>in</strong>dicators of life/II.5 Fig. II.5.7.4/1. Backscatter Mössbauer spectra of martian analogues obta<strong>in</strong>ed with MIMOS II. From top to bottom: HWMK600, palagonitic tephra sample from Mauna Kea; HWMK24, jarositic tephra sample from Mauna Kea; BCS-301, chemical standard derived from an iron ore deposit; AKB-1, amygdaloidal basalt from <strong>the</strong> Keweenawan pen<strong>in</strong>sula; MAN-74-342A, impact melt rock from <strong>the</strong> Manicouagan crater <strong>in</strong> Canada. (Morris et al., 1998) (Courtesy G. Kl<strong>in</strong>gelhöfer) 141
SP-1231 142 atures should be per<strong>for</strong>med: at least one dur<strong>in</strong>g <strong>the</strong> lowest temperature period (night) and one dur<strong>in</strong>g <strong>the</strong> highest temperature period (day). To acquire one spectrum will take approximately 8-12 h depend<strong>in</strong>g on <strong>the</strong> phases and <strong>the</strong> total iron content. <strong>The</strong> temperature variation <strong>for</strong> one spectrum should be not larger than about 10ºC. In case of larger variations, spectra <strong>for</strong> different temperature ranges will be stored separately, result<strong>in</strong>g <strong>in</strong> an <strong>in</strong>creased total measur<strong>in</strong>g time (depend<strong>in</strong>g on <strong>the</strong> number of temperature <strong>in</strong>tervals required). <strong>The</strong> MIMOS II <strong>in</strong>strument developed at <strong>the</strong> Technische Universität Darmstadt, Germany, was scheduled to fly on Russia’s Mars-98 rover mission. This <strong>in</strong>strument has been developed and a prototype built and partially qualified <strong>for</strong> <strong>the</strong> Russian- German Nanokhod <strong>in</strong>strument deployment device (IDD; Max-Planck Institute <strong>for</strong> Cosmochemistry, Ma<strong>in</strong>z, Germany), which was scheduled to fly on Europe’s Inter- MarsNet mission. A MIMOS II prototype was successfully tested on <strong>the</strong> Rocky-7 prototype rover dur<strong>in</strong>g <strong>the</strong> May 1997 field tests <strong>in</strong> <strong>the</strong> US Mojave Desert, tak<strong>in</strong>g data under semi-real conditions. <strong>The</strong> Mössbauer spectrometer is a simple <strong>in</strong>strument. <strong>The</strong> ma<strong>in</strong> parts are <strong>the</strong> radiation source, <strong>the</strong> velocity transducer (drive), <strong>the</strong> Silicon PIN (positive-<strong>in</strong>tr<strong>in</strong>sicnegative) radiation detectors and <strong>the</strong>ir pre- and ma<strong>in</strong>-amplifiers, and <strong>the</strong> <strong>in</strong>strument control and data acquisition system. <strong>The</strong> standard 57 Co radiation source is used, embedded <strong>in</strong> a solid rhodium matrix, which is mounted <strong>in</strong> a titanium holder. This design is <strong>in</strong>tr<strong>in</strong>sically simple, rugged and is made very safe through <strong>the</strong> shield<strong>in</strong>g design. <strong>The</strong> drive is a unique m<strong>in</strong>iature double-voice coil electromechanical drive, developed at TU Darmstadt. <strong>The</strong> drive system has already undergone environmental test<strong>in</strong>g at +20ºC to -80ºC, as well as vibration and shock tests <strong>in</strong> <strong>the</strong> frequency range specified <strong>for</strong> <strong>the</strong> Russian Mars-98 lander mission. <strong>The</strong> Si-PIN-diodes toge<strong>the</strong>r with <strong>the</strong> pre- and ma<strong>in</strong>-amplifiers and <strong>the</strong> bias supply have been tested <strong>in</strong> <strong>the</strong> same way (shock, frequency, temperature). Prototype versions operated successfully at even unfavourably high temperatures dur<strong>in</strong>g <strong>the</strong> Rocky-7 field tests. <strong>The</strong> <strong>in</strong>strument control unit and data acquisition system, <strong>in</strong>clud<strong>in</strong>g <strong>the</strong> software, successfully operated <strong>in</strong> a number of laboratory measurements as well as <strong>the</strong> Rocky-7 field tests <strong>in</strong> May 1997. For <strong>the</strong> Mars Surveyor 2001 A<strong>the</strong>na mission, <strong>the</strong> MIMOS II <strong>in</strong>strument will be split <strong>in</strong>to two parts: a detector head mounted on <strong>the</strong> arm, and <strong>the</strong> <strong>in</strong>strument control and data acquisition unit located <strong>in</strong> <strong>the</strong> Rover’s warm electronics box. <strong>The</strong> total weight is about 500 g, with <strong>the</strong> sensor head itself about 400 g. <strong>The</strong> power consumption is of <strong>the</strong> order of 1.5 W. <strong>The</strong> radioactive Mössbauer source will have an <strong>in</strong>tensity of about 300 mCi at launch. II.5.7.5 Ion/Electron Probes, X-ray Spectroscopy For chemical composition, <strong>the</strong> ion probe is heavy and an alternative could be electron probe analysis. In<strong>for</strong>mation on crystal structure could be provided by X-ray spectroscopy, if m<strong>in</strong>iaturised <strong>for</strong> application to planetary exploration missions. <strong>The</strong>re are two US teams from <strong>the</strong> NASA Ames Research Center and Los Alamos National Laboratory work<strong>in</strong>g on <strong>the</strong> m<strong>in</strong>iaturisation of X-ray diffraction <strong>in</strong>struments (XRDs). <strong>The</strong>re are no prototypes available yet. <strong>The</strong> development of flight <strong>in</strong>struments will require at least 2 years, if successful at all. II.5.7.6 IR Spectroscopy II.5.7.6.1 Molecular Spectroscopy IR spectroscopy at 0.8-4.0 µm can 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 been found <strong>in</strong> only one martian meteorite, <strong>the</strong> structure of <strong>the</strong> broad absorption
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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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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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