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

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team I: exobiology and <strong>the</strong> mars surface environment/II.4 Site 1: Marca Crater and adjacent putative crater lakes (Memnonia) Lacustr<strong>in</strong>e and Deltaic Deposits 10.4ºS/158.2ºW Crater diameter: 84 km Elevation of <strong>the</strong> substratum: 2 km Elevation of <strong>the</strong> crater floor: about 1 km or less <strong>The</strong>se craters are located <strong>in</strong> <strong>the</strong> nor<strong>the</strong>rn area of Memnonia <strong>in</strong> a Noachian geological unit. It is quite probable that Marca Crater <strong>for</strong>med dur<strong>in</strong>g <strong>the</strong> Late Heavy Bombardment. <strong>The</strong>re is evidence that <strong>the</strong> crater has been filled with water <strong>in</strong> more recent times. <strong>The</strong> floor shows a crater population largely below 1 km <strong>in</strong> diameter, and <strong>the</strong> possible age <strong>for</strong> <strong>the</strong> floor unit lies <strong>in</strong> <strong>the</strong> Amazonian. <strong>The</strong> ma<strong>in</strong> evidence <strong>for</strong> <strong>the</strong> presence of water is <strong>the</strong> Gilbert-type delta at <strong>the</strong> rim. This evidence, coupled with <strong>the</strong> flat young floor and <strong>the</strong> rema<strong>in</strong>s of <strong>the</strong> eroded and flooded central peak, suggests that <strong>the</strong> crater acted as a lake <strong>in</strong> one or more episodes. <strong>The</strong> crater floor probably conta<strong>in</strong>s ridges of young w<strong>in</strong>d-blown sand. However, this loose detritus is probably <strong>in</strong> patches, as suggested by <strong>the</strong> variation <strong>in</strong> albedo that strongly supports <strong>the</strong> possibility of <strong>the</strong> lacustr<strong>in</strong>e beds be<strong>in</strong>g exposed. <strong>The</strong> nature of <strong>the</strong> lacustr<strong>in</strong>e deposits cannot be identified; <strong>the</strong>re is probably clastic detritus (sand and pebbles) from <strong>the</strong> erosion of <strong>the</strong> crater rims matched by an <strong>in</strong>ternal dra<strong>in</strong>age pattern. <strong>The</strong>re could also be limestone and clay. <strong>The</strong> site would allow old Noachian rocks and younger lacustr<strong>in</strong>e deposits to be <strong>in</strong>vestigated. In <strong>the</strong> area <strong>the</strong>re are several craters that have been lacustr<strong>in</strong>e bas<strong>in</strong>s dur<strong>in</strong>g <strong>the</strong> Late Hesperian and Amazonian eras (Farmer & Landheim, 1994), <strong>in</strong>clud<strong>in</strong>g <strong>the</strong> Gusev Crater (Gr<strong>in</strong> & Cabrol, 1997). All of <strong>the</strong>m are alternative land<strong>in</strong>g sites because <strong>the</strong> sett<strong>in</strong>gs are basically similar to Marca Crater. Gusev Crater is actually <strong>the</strong> only crater of this type that received a large amount of sediment by a large-scale fluvial channel. Fig. II.4.7/1. Site 1: Marca Crater is one of several impact structures <strong>in</strong> Memnonia show<strong>in</strong>g evidence of stand<strong>in</strong>g bodies of water. (Vik<strong>in</strong>g image, NASA.) 123
SP-1231 124 Site 2: Apol<strong>in</strong>aris Patera Volcano and Volcanogenic Units 8.6ºS/187.5ºW Elevation: 0-1 km Apol<strong>in</strong>aris Patera is a volcanic complex <strong>in</strong> <strong>the</strong> equatorial area of Mars at a relatively low elevation. <strong>The</strong> age is probably Hesperian (Scott et al., 1993). <strong>The</strong> patera itself is not of great exobiology <strong>in</strong>terest, but <strong>the</strong>re is a lot of evidence <strong>for</strong> <strong>the</strong> presence of water (Gulick, 1998): chaotic zones, lobate ejecta and channels. Ow<strong>in</strong>g to <strong>the</strong> volcanic activity, coupled with <strong>the</strong> presence of water, <strong>the</strong> most probable processes are hydro<strong>the</strong>rmal. <strong>The</strong>se hydro<strong>the</strong>rmal systems probably existed well <strong>in</strong>to <strong>the</strong> Amazonian era (Gulick, 1998), witnessed by <strong>the</strong> prist<strong>in</strong>e crater associated with <strong>the</strong> volcanic edifice. Fluids were likely ejected from <strong>the</strong> volcano on to <strong>the</strong> surround<strong>in</strong>g pla<strong>in</strong>s, <strong>for</strong>m<strong>in</strong>g a ra<strong>the</strong>r large hydro<strong>the</strong>rmal site. Evidence of (hydro<strong>the</strong>rmal) sapp<strong>in</strong>g occur <strong>in</strong> <strong>the</strong> sou<strong>the</strong>rn area. Among <strong>the</strong> several possible land<strong>in</strong>g areas, <strong>the</strong> sou<strong>the</strong>rn portion of <strong>the</strong> patera probably has <strong>the</strong> greatest potential <strong>for</strong> exobiology. <strong>The</strong>re is a large fan-shaped channel complex <strong>in</strong> this area. Erosion of <strong>the</strong> volcano’s flanks has probably exhumed large quantities of old volcanic units, and hydro<strong>the</strong>rmal spr<strong>in</strong>gs are ra<strong>the</strong>r probable. A land<strong>in</strong>g site at around 12ºS/185.5ºW (Gulick, 1998) would be suitable <strong>for</strong> exobiological exploration. Fig. II.4.7/2. Site 2: Apol<strong>in</strong>aris Patera is a volcano with extensive features suggest<strong>in</strong>g <strong>the</strong> presence of water and, consequently, hydro<strong>the</strong>rmal activity. (Vik<strong>in</strong>g image, NASA.)
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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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Page 161 and 162: SCIENTIFIC METHOD AND REQUIREMENTS
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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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