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P. R. Christensen (ASU)
The Thermal Emission Imaging System (THEMIS) onboard Mars Odyssey began studying the surface and atmosphere of Mars in February 2002 using thermal infrared (IR) multi-spectral imaging between 6.5 and 15 µm, and visible/near-IR images from 450 to 850 nm. Regional-scale infrared mapping shows that Mars has both regional and local geologic units delineated by their thermophysical properties. In Meridiani Planum these units imply a complex history involving changes in the nature of volcanic units, the environment of deposition of sedimentary units, and/or the degree of lithification or cementation of initially unconsolidated units. Mars has km-scale exposures of bedrock, and rocky surfaces are commonly observed on slopes and scarps, demonstrating that the production or exposure rate of rock locally exceeds the rate of rock burial or breakdown. In places, thermally distinct ejecta deposits with a wide range of thermophysical properties are observed around craters of varying sizes. This variation in the preservation of the infrared signature of crater ejecta may be associated with crater age. Where large fields of sand dunes occur, the dunes are typically coarser-grained than the interdune surfaces, suggesting that finer-grained material is accumulating where active sand motion may be limited. Surfaces known to be mantled by air-fall dust, such as the Tharsis and Arabia provinces, also appear completely mantled at THEMIS 100-m per pixel resolution. THEMIS multi-spectral infrared observations show significant potential for compositional mapping at 100-m scales, as demonstrated by the identification of olivine-rich basaltic units on the floor of Ganges Chasma. Polar observations have confirmed the presence of CO2 slab ice and the presence of H2O exposed at the surface of the south polar summer cap. The visible imager also has obtained information on the color properties of the surface and of atmospheric aerosols at the highest spatial resolution yet obtained from Mars orbit.
This work was supported by the NASA Mars Odyssey Flight Project.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.