Global distribution of bedrock exposures on Mars using THEMIS high-resolution thermal inertia
Article first published online: 4 NOV 2009
Copyright 2009 by the American Geophysical Union.
Journal of Geophysical Research: Planets (1991–2012)
Volume 114, Issue E11, November 2009
How to Cite
2009), Global distribution of bedrock exposures on Mars using THEMIS high-resolution thermal inertia, J. Geophys. Res., 114, E11001, doi:10.1029/2009JE003363., , , and (
- Issue published online: 4 NOV 2009
- Article first published online: 4 NOV 2009
- Manuscript Accepted: 21 JUL 2009
- Manuscript Revised: 26 JUN 2009
- Manuscript Received: 12 FEB 2009
 We investigate high thermal inertia surfaces using the Mars Odyssey Thermal Emission Imaging System (THEMIS) nighttime temperature images (100 m/pixel spatial sampling). For this study, we interpret any pixel in a THEMIS image with a thermal inertia over 1200 J m−2 K−1 s−1/2 as “bedrock” which represents either in situ rock exposures or rock-dominated surfaces. Three distinct morphologies, ranked from most to least common, are associated with these high thermal inertia surfaces: (1) valley and crater walls associated with mass wasting and high surface slope angles; (2) floors of craters with diameters >25 km and containing melt or volcanics associated with larger, high-energy impacts; and (3) intercrater surfaces with compositions significantly more mafic than the surrounding regolith. In general, bedrock instances on Mars occur as small exposures (less than several square kilometers) situated in lower-albedo (<0.18), moderate to high thermal inertia (>350 J m−2 K−1 s−1/2), and relatively dust-free (dust cover index <0.95) regions; however, there are instances that do not follow these generalizations. Most instances are concentrated in the southern highlands, with very few located at high latitudes (poleward of 45°N and 58°S), suggesting enhanced mechanical breakdown probably associated with permafrost. Overall, Mars has very little exposed bedrock with only 960 instances identified from 75°S to 75°N with likely <3500 km2 exposed, representing ≪1% of the total surface area. These data indicate that Mars has likely undergone large-scale surface processing and reworking, both chemically and mechanically, either destroying or masking a majority of the bedrock exposures on the planet.