TES discovered that unweathered volcanic minerals dominate the Martian dark regions. The lack of large-scale clay and carbonate mineral deposits means Mars has seen much less chemical weathering than Earth. In turn, this indicates Mars’ geologic history has been mostly cold and dry.
Colors ranging from magenta to purple-blue map large exposures of olivine-rich rocks in the Nili Fossae region of Syrtis Major. The olivine, which weathers quickly on exposure to water, is about four times as extensive as scientists previously thought, suggesting the Martian climate has been mostly cold and dry. The image was taken by the Thermal Emission Imaging System on Mars Odyssey, and it maps olivine first discovered by TES. This image is about 350 kilometers (220 miles) wide.
- Hamilton, V.E., and P.R.Christensen, Evidence for extensive olivine-rich bedrock in Nili Fossae, Mars, Geology, 33, 433-436, 2005.
- Rogers, A.D., P.R.Christensen, and J.L. Bandfield, Compositional heterogeneity of the ancient martian crust: Analysis of Ares Vallis bedrock with THEMIS and TES data, J. Geophys. Res., 110, E05010, doi:10.1029/2005JE002399, 2005.