Identification of a basaltic component on the Martian surface from Thermal Emission Spectrometer data

Abstract. The Mars Global Surveyor Thermal Emission Spectrometer (TES) instrument collected 4.8 3 106 spectra of Mars during the initial aerobraking and science-phasing periods of the mission (September 14, 1997, through April 29, 1998). Two previously developed atmosphere-removal models were applied to data from Cimmeria Terra (258S, 2138W). The surface spectra derived for these two models agree well, indicating that the surface and atmosphere emission can be separated and that the exact atmosphere-removal model used has little effect on the derived surface composition. The Cimmeria spectra do not match terrestrial high-silica igneous rocks (granite and rhyolite), ultramafic igneous rocks, limestone, or quartz- and clay-rich sandstone and siltstone. A particulate (sand-sized) sample of terrestrial flood basalt does provide an excellent match in both spectral shape and band depth to the Cimmeria spectrum over the entire TES spectral range. No unusual particle size effects are required to account for the observed spectral shape and depth. The implied grain size is consistent with the thermal inertia and albedo of this region, which indicate a sand-sized surface with little dust. The identification of basalt is consistent with previous indications of pyroxene and basalt-like compositions from visible