High thermal inertia surfaces and the physical nature of the upper martian crust

Details High thermal inertia surfaces and the physical nature of the upper martian crust High thermal inertia surfaces and the physical nature of the upper martian crust

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p33b1464e&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #P33B-1464

Physics

5410 Composition (1060, 3672), 5415 Erosion And Weathering, 5460 Physical Properties Of Materials, 5464 Remote Sensing, 5470 Surface Materials And Properties

Scientific paper

An investigation of martian high thermal inertia surfaces has been made using Thermal Emission Imaging System (THEMIS) one hundred meter per pixel nighttime temperature data. High thermal inertia surfaces or interpreted bedrock are defined as any pixel in a THEMIS image with a thermal inertia over 1200 J K- 1m-2s-1/2) and may refer to in situ rock exposures or rock-dominated surfaces. Three distinct morphologies, ranked from most to least common, are associated with these high inertia surfaces: 1) valley and crater walls associated with mass wasting and high surface slope angles, 2) crater floors related to melting and re-crystallization associated with large (typically >25 km), high energy impacts, 3) plains surface with compositions significantly more mafic than the surrounding regolith, possibly indicating that the martian regolith has been processed, both chemically and mechanically. Overall, Mars has very little exposed bedrock or rocky material with only 960 instances identified from 75°N to 75°S. In general, bedrock instances occur in lower albedo (<0.18), moderate thermal inertia (>350 J K-1m-2s-1/2), and relatively dust free (DCI <0.95) areas. While many locations on Mars satisfy these conditions and have expected morphologies (e.g. steep slopes in Valles Marineris), observed bedrock instances are surprisingly rare. Most instances are concentrated in the southern highlands, with very few located at high latitudes (>45°N and <58°S). The latitudinal asymmetry observed in this data indicates a process that preferentially destroys or masks bedrock at lower latitudes in the north. Several processes likely play a role in destroying or masking a majority of the bedrock on the planet, including enhanced mechanical breakdown associated with permafrost at high latitudes and chemical and/or mechanical weathering associated with the formation of regolith fines from mafic precursor material [Bandfield and Rogers, 2008]. This distinct lack of bedrock indicates that Mars has likely undergone large-scale processing and reworking of the upper crust. Bandfield, J.L. and A.D. Rogers (2008) Geology, doi:10.1130/G24724A.

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