Surface Kinetic Temperatures and Nontronite Single Scattering Albedo Spectra From Mars Reconnaissance Orbiter CRISM Hyperspectral Imaging Data Over Glen Torridon, Gale Crater, Mars

The Mars Reconnaissance Orbiter Compact Imaging Spectrometer for Mars (CRISM) covers the spectral range from 0.362 to 3.92 mu m with a midafternoon local solar time data acquisition. For equatorial to midlatitudes, depending on the season and surface materials, wavelengths longer than similar to 2.65 mu m exhibit spectral radiances on sensor that include sunlight and thermal-emission related terms. We developed a radiative transfer based neural network approach to model both solar and emitted terms in which surface kinetic temperatures are retrieved for each image pixel, together with single scattering albedo spectra, over the full CRISM wavelength range. We applied the method to along-track oversampled scene FRT00021C92 over Glen Torridon within Gale Crater, where the Curiosity rover traversed and acquired remote sensing and in-situ data. Synergistic analysis of orbital and rover-based data, coupled with laboratory analyses of ferric-rich smectites, provide a self-consistent set of results for the presence of desiccated nontronite associated with Murray formation mudstones exposed as periodic bedrock ridges located just to the south of Vera Rubin ridge. The desiccated nature is consistent with Curiosity's CheMin data, which for Glen Torridon drill samples indicate an abundance of nontronite having a collapsed structure resulting from loss of interlayer H2O. Plain Language Summary The Mars Reconnaissance Orbiter's Compact Imaging Spectrometer for Mars (CRISM) is a hyperspectral imaging instrument that covers the wavelength range from 0.362 to 3.92 mu m. The longer wavelength data contain radiative streams from both solar and thermal emission. We implemented a neural network approach to model both radiative streams in order to retrieve surface kinetic temperatures and single scattering albedo spectra for each pixel in CRISM scenes and across the full wavelength region. Application of results for a scene centered over Glen Torridon, and synergistic comparison to Curiosity rover measurements, show the ubiquitous presence of a hydrated signature, even for basaltic sand fields, together with the presence of highly desiccated nontronite within mudstone deposits.