THE MINERALOGY OF THE MER LANDING SITES AS INVESTIGATED BY THE MINI-TES EXPERIMENT

The Mini-TES instruments on Spirit and Opportunity have studied the mineralogy and thermophysical properties at Gusev Crater and the Meridiani Plains. At Gusev undisturbed soil spectra closely match MGS TES bright-region dust spectra, with features interpreted to be due to minor carbonates and bound water. Rocks are olivine-rich basalts with varying degrees of dust and other coatings, closely matching the predictions from TES. Dark-toned soil observed on rover-disturbed surfaces is likely derived from rocks and has a derived mineralogy, with uncertainties of 5-10%, of 45% pyroxene (20% Ca-rich pyroxene, 25% pigeonite), 40% sodic/intermediate plagioclase, and 15% olivine (Fo45 ±5-10). Aeolian drift material has a unique spectral character with higher oxide abundances than disturbed soil. Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. At Meridiani, the Mini-TES has confirmed the presence of coarse crystalline hematite and olivine basalt sands predicted from orbital TES spectroscopy. Light-toned outcrops exposed in craters are composed of 20-40% sulfates, with hematite, and sheet silicate/glass. The sulfate component is dominated by Ca and Mg cations, with Fe sulfate (jarosite) only a minor component. The spherical granules that are widespread on the plains are essentially pure hematite, with no silica, carbonates, sulfates, encased silicates, or other oxides detected. Basaltic materials have plagioclase to pyroxene ratios of 1.5 to 1, appear to contain minor olivine, and are similar in mineralogy to the basalt mapped throughout the equatorial region. A rock dubbed “Bounce Rock” is dominated by clinopyroxene and is closer in mineralogy to the basaltic SNC meteorites. The bright material accumulated in the Eagle crater wind streaks and on several flat-lying rocks has the mineral composition of TES-derived global dust.