Mathematics – Logic
Scientific paper
May 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agusm.p32a..06c&link_type=abstract
American Geophysical Union, Spring Meeting 2004, abstract #P32A-06
Mathematics
Logic
5410 Composition, 5464 Remote Sensing, 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. Infrared spectral mapping by the TES and THEMIS orbital instruments has shown that the martian surface is dominated by unweathered volcanic rocks, including olivine-rich basalts in numerous areas. THEMIS 100-m scale multispectral imaging reveals compositional variations at these scales. However these compositional differences are due to differences in the composition of igneous materials. Regions of high (~20 percent) olivine abundance basalts have been mapped at the scales of individual flows and rock layers, including exposures at multiple layers with the Valles Marineris system, demonstrating that large regions of Mars have not experienced significant surface or sub-surface water at any time in their history. THEMIS has not detected mineralogical evidence for carbonate rock layers at 100-m scales, despite the discovery by the MGS TES of minor carbonate in the martian dust. The existing carbonates can be produced by surface-atmosphere interactions, without requiring the presence and erosion of a carbonate rock source. THEMIS imaging has, however, shown evidence for extensive ice deposits in the mid- to high-latitude regions, some of which show evidence for recent downslope flow. These mantles preferentially occur on pole-facing slopes 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. A pervasive surface mantle found from 30 to 50o 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 mid-latitude mantles may be the same ice-rich material detected by the GRS at high latitudes, 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 severely limited the degree of global chemical weathering.
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