MINI-TES DERIVED CHEMICAL ABUNDANCES AT GUSEV CRATER AND MERIDIANI PLANUM: IMPLICATIONS FOR GLOBAL SURFACE COMPOSITIONS

The Miniature Thermal Emission Spectrometer (Mini-TES) experiments provide remote measurements of mineral abundances and compositions at the Spirit and Opportunity landing sites of Gusev Crater and Meridiani Planum. Olivine basaltic sands and rocks are identified at Gusev Crater, along with variable amounts of fine-grained dust and other possible coatings. Olivine basaltic sands and coarse crystalline hematite, a pyroxene-rich basaltic rock, fine-grained dust, and outcrops composed of sulfates, hematite, and sheet silicates/glass are identified at Meridiani Planum. The occurrence of olivine basalt was predicted at both landing sites by observations from the orbiting Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). Furthermore, Mini-TES spectra of basaltic sands are very similar to a global average TES basalt spectrum in the overall spectral shape and positions of spectral features. Ground-truth observations of the mineralogy and chemistry of olivine basalt from the Mini-TES, Alpha Particle X-ray Spectrometer (APXS), and Mössbauer Spectrometer (MB) are significant because of the extensive distribution and high-abundance of olivine basalt on Mars and the inferred petrogenesis and evolution of a basaltic crust. In this study, we calculate bulk chemical oxide abundances of surface materials from Mini-TES derived mineral abundances and compositions and compare results to APXS and MB observations to examine the accuracy of thermal emission derived chemistry. We then focus on comparisons of Mini-TES and TES derived chemistries of basalt to determine the limits to which we can constrain bulk compositions and the depth and degree of partial melting of their source regions. Local ground-truth observations of the bulk mineralogy and chemistry of a global basaltic unit provide insight to the degree of differentiation of the crust and mantle.