Mathematics – Logic
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufm.p32b..01c&link_type=abstract
American Geophysical Union, Fall Meeting 2003, abstract #P32B-01
Mathematics
Logic
5410 Composition, 5416 Glaciation, 5470 Surface Materials And Properties, 6225 Mars
Scientific paper
Evidence from a variety of sources suggests that Mars has a significant water inventory. However, it appears that this inventory has been frozen throughout much of Mars history. The THEMIS camera has detected layers of exposed olivine-rich basalt 4.5 km below the surface in Ganges Chasma, indicating that this region has not experienced significant surface or sub-surface water at any time in its history. In addition, THEMIS has not detected mineralogical evidence for carbonate layers at 100-m scales, despite the discovery by the MGS TES of minor carbonate in the martian dust. THEMIS has, however, shown evidence for extensive ice deposits in the mid- to high-latitude regions, some of which show evidence for recent downslope flow. THEMIS images show that mantles on pole-facing slopes occur preferentially in mid-latitudes and are interpreted to be remnants of once-extensive snows deposited during recent periods of high obliquity. Melting of these deposits during intervening warmer periods may form the young gullies that are also observed at these latitudes. High (greater than 50 percent volume) water-ice abundances have been found in the upper few meters at high-latitudes by the Odyssey Gamma-Ray and Neutron Spectrometer Teams, suggesting that this ice also formed at the surface rather than in pores. A pervasive surface mantle found from 30 to 50° in both hemispheres has been interpreted by Mustard et al. (2001) to result from ice-cemented soils that have formed recently and are currently being devolatilized. The poleward transition from a dissected to continuous surface on this mantle corresponds to a sharp increase in near-surface ice abundance seen by the GRS, suggesting that the mid-latitude portion of these mantles may be the same ice-rich material but whose upper few meters have been thoroughly desiccated. Together these observations suggest extensive mid-latitude surface ice deposits that come and go on time scales of 50,000 to several million years. Limited melting may occur in these deposits, but the low temperatures and short durations of liquid water appear to have limited the degree of chemical weathering.
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