from Part III - Mineralogy and Remote Sensing of Rocks, Soil, Dust, and Ices
Published online by Cambridge University Press: 10 December 2009
ABSTRACT
The Thermal Emission Imaging System (THEMIS) began mapping Mars in 2002 on the Mars Odyssey spacecraft. This instrument provides nine infrared and five visible surface-sensing and atmospheric bands, with spatial resolutions of 100 m in the IR and 18 m in the visible. THEMIS data have been used to investigate the composition and physical properties of the surface and polar ices, as well as to study atmospheric temperature, dust, and water vapor. THEMIS provides an excellent complement to the hyperspectral, 3–6 km spatial resolution Thermal Emission Spectrometer (TES) observations, and the two instruments have been used together to map the distribution of geologic units and to determine their detailed mineralogy. Among the major findings to date is the discovery of a diversity in volcanic compositions, from ultramafic olivine-rich basalts through basalts, dacite cones and flows, and granitic rocks uplifted by impact. These observations indicate that the Martian crust, while dominated by basalt, has undergone many of the processes of igneous differentiation that occur on Earth. THEMIS has not detected any carbonate outcrops at 100 m scales, suggesting that carbonate rocks have not formed on Mars and has also not detected any evidence for near-surface volcanic activity, liquid water, or ice that is close enough to the surface to produce a measurable thermal anomaly. THEMIS nighttime temperature measurements have shown the existence of exposed bedrock at 100 m to km scales, and layered materials of differing physical properties, with inferred differences in the processes that deposited or consolidated them.
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