Review of the MEPAG Report on Mars Special Regions (2015) / Chapter Skim
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3 Martian Geological and Mineralogical Features Potentially Related to Special Regions
3 Martian Geological and Mineralogical Features Potentially Related to Special Regions
Pages 13-25
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From page 13... ...
The detection of deliquescent minerals and the presence of water in the form of subsurface ice, snow, and liquid brines were considered in view of ambient martian temperature and pressure conditions and the potential bioavailability of water. In general, the review committee agrees with the relevant findings and conclusions in the SR-SAG2 report relating to these topics.
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From page 14... ...
14 REVIEW OF THE MEPAG REPORT ON MARS SPECIAL REGIONS FIGURE 3.1 Recurring slope lineae (RSL) in a crater on the floor of central Valles Marinaris.
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From page 15... ...
of methane and identifying the process(es) by which it is produced and/or released must remain key mission priorities because of the high potential that such processes operate at temperatures and water activity values that define Special Regions.
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From page 16... ...
; beneath or in the lower boundary layer of subsurface clathrates and the cryosphere; and in cryopegs, the lenses of ground that contain over-cooled (–9°C to –11°C) water brines that could periodically source so-called recurring slope lineae (see the next section of this chapter)
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From page 17... ...
Recent or ancient subsurface methane may be stored within lattice-structured methane hydrates called clathrates and released over time, a source of modern atmospheric methane that may have formed in the past. Concentrations of atmospheric methane can drop due to redistribution or photochemical sinks.
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From page 18... ...
Such detections are not used to distinguish Special Regions on Mars. Revised Finding 2-4: Organic compounds are present on Mars (or in the martian subsurface)
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From page 19... ...
They report seasonal change and incremental growth of slope streaks near Olympus Mons and Arabia Terra, in direct contrast to the SR-SAG2 report's generalization for the slope streaks as a phenomenon distinct from RSL. Moreover, recent analyses of the slopes on which slope streaks form suggest they do not have significant inertia that would be expected for
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From page 20... ...
This review committee therefore suggests a slightly revised Finding 4-8. SR-SAG2 Finding 4-8: The 2006 Special Regions analysis did not consider dark/light slope streaks to be definitive evidence for water.
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From page 21... ...
Revised Finding 4-9: A conservative interpretation of the evidence suggests that polar dark dune streaks could potentially involve liquid brines but only in the presence of heating mechanisms such as solid-state greenhouse effects. The discovery of soft, segregated ice in the shallow subsurface of Mars by NASA's Phoenix lander (Rennó et al.
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From page 22... ...
Revised Finding 5-7: We do not have accepted models to explain the presence of segregated ice on Mars yet. However, a conservative interpretation of the evidence suggests that processes involving liquid brines (likely at temperatures below –25ºC)
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From page 23... ...
Only when the salts are in direct contact with water ice can bulk deliquescence occur in Mars environmental conditions. Thus, liquid aqueous solutions could form temporarily during diurnal cycles only where salts and ground ice co-exist in the shallow martian subsurface and on the surface when frost or snow are deposited on saline soils (Fischer et al.
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From page 24... ...
However, snow could melt if deposited on salts with eutectic temperature lower than that at which sublimation occurs, possibly creating temporary Special Regions. There appears to be substantial subsurface ice on Mars, even in equatorial regions (e.g., Vincendon et al.
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From page 25... ...
If organic compounds are also present on Mars, then heterotrophic microbes may also find a home there. In conclusion, there could be a number of possible primary sources of the necessary ingredients for life inside caves and subsurface cavities on Mars, and therefore, they are best classified as Uncertain Regions and treated as Special Regions until proven otherwise.
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