An Astrobiology Strategy for the Exploration of Mars (2007) / Chapter Skim
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4 Characteristics of Sites for Astrobiological Investigation
4 Characteristics of Sites for Astrobiological Investigation
Pages 57-68
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From page 57... ...
The proposed target mineralogies and lithologies, which include putative hydrothermal systems, evaporites, sediments, iron oxides, and clay minerals, are the best targets to find possible evidence of FIGURE 4.1 This delicate fan shape is the product of the long-term distribution of sediments by flowing liquid water. Image from the Mars Orbiter Camera on the Mars Global Surveyor spacecraft courtesy of NASA/JPL/Malin Space Science Systems.
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From page 58... ...
1 The precipitation that occurs owing to supersaturation can also occur in the subsurface where hydrothermal flow is driven by a buried heat source. The emplacement of igneous intrusives such as dikes infiltrating sedimentary rocks can generate subsurface hydrothermal flow and enhance mineralization reactions.
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From page 59... ...
Sites and Samples for Biosignatures of Past Life The processes that lead to preservation of biosignatures on Earth are far from fully understood. Although researchers expect their martian counterparts to follow the same general sets of processes, the conditions on Mars that may have led to biosignature preservation are poorly constrained, and hence, the matrix of target environments is necessarily varied, including sites and samples with an uncertain potential for success.
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From page 60... ...
0 AN ASTROBIOLOGY STRATEGY FOR THE EXPLORATION OF MARS FIGURE 4.2 Layering in an unnamed crater in Meridiani Planum. The crater was once partly buried by layered deposits that have since been largely removed, leaving remnants of the former cover as mesas within the crater.
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From page 61... ...
The abundance of iron minerals on Mars, including igneous olivine, iron oxide dust, and sedimentary hematite, provide potential redox reaction sites that may support life and may leave mineralogical evidence of past life. A target for this exploration might include sites where especially high amounts of energy are available in the form of, for example, reduced iron minerals juxtaposed with likely oxidants.
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From page 62... ...
However, it may persist in the shallow subsurface as part of an extensive groundwater system. Target environments where subsurface water -- and hence present life -- may be most likely include the following: • Sediments and sedimentary rocks where porosity and permeability are characteristic of aquifers; • reas below surface features related to recent aqueous processes (e.g., gullies and young outflow channels)
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From page 63... ...
• Glacial ice. Deposits left by cold-based glaciers have been identified on Mars, particularly on the northwest flanks of the large Tharsis volcanos.23 They probably formed in recent geological times during periods of high obliquity and might therefore still contain dormant lifeforms or their remnants.
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From page 64... ...
These include metamorphism/reduction of carbonates, serpentinization of olivine and subsequent abiotic reduction of CO2 with the generated H2, and recycling/thermal cracking of deeply buried complex organic matter (e.g., kerogen)
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From page 65... ...
Wang, and A Yen, "The Rocks of the Columbia Hills," Journal of Geophysical Research 111:E02S11, doi:10.1029/2005JR002562, 2006.
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From page 66... ...
Maillard, and T.C. Owen, "Detection of Methane in the Martian Atmosphere: Evidence for Life?
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