Mineralogical characterization of Mars Science Laboratory candidate landing sites from THEMIS and TES data

Data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and the Mars Odyssey Thermal Emission Imaging System (THEMIS) instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the Mars Science Laboratory (MSL) mission. Candidate regions examined in this study are Eberswalde crater, Gale crater, Holden crater, Mawrth Vallis, Miyamoto crater, Nili Fossae Trough, and south Meridiani Planum. Compositional units identified in each region from TES and THEMIS data are distinguished by variations in hematite, olivine, pyroxene and high-silica phase abundance, whereas no units are distinguished by elevated phyllosilicate or sulfate abundance. Though phyllosilicate minerals have been identified in all sites using near-infrared observations, these minerals are not unambiguously detected using either TES spectral index or deconvolution analysis methods. For some of the sites, small phyllosilicate outcrop sizes relative to the TES field of view likely hinder phyllosilicate mineral detection. Porous texture and/or small particle size (<∼60 μm) associated with the phyllosilicate-bearing surfaces may also contribute to non-detections in the thermal infrared data sets, in some areas. However, in Mawrth Vallis and Nili Fossae, low phyllosilicate abundance (<10–20 areal %, depending on the phyllosilicate composition) is the most likely explanation for non-detection. TES data over Mawrth Vallis indicate that phyllosilicate-bearing surfaces also contain significant concentrations (>15%, possibly up to ∼40%) of a high-silica phase such as amorphous silica or zeolite. High-silica phase abundance over phyllosilicate-bearing surfaces in Mawrth Vallis is higher than that of surrounding surfaces by 10–15%. With the exception of these high-silica surfaces in Mawrth Vallis, regions examined in this study exhibit similar bulk mineralogical compositions to that of most low-albedo regions on Mars; the MSL scientific payload will thus be able to provide important information on surface materials typical of low-albedo regions in addition to investigating the origin of phyllosilicate and/or sulfate deposits. With the exception of Gale crater, all of the landing sites have relatively low dust cover compared to classic high-albedo regions (Tharsis, Arabia and Elysium) and to previous landing sites in Gusev Crater, Utopia Planitia, and Chryse Planitia.