Integrating CRISM and TES hyperspectral data to characterize a halloysite-bearing deposit in Kashira crater, Mars

We present morphologic observations and spectral modeling results of a large, kaolin-group mineral-bearing deposit within Kashira crater in the southern highlands of Mars. We employ both non-linear unmixing of Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) visible to near-infrared (VNIR) reflectance data and linear unmixing of Thermal Emission Spectrometer (TES) thermal infrared (TIR) emissivity data to quantitatively analyze the kaolin-group mineral within this deposit. We use a novel approach for quantitative analysis of CRISM data through non-linear unmixing with in-scene, orbitally-derived endmembers combined with laboratory measured endmembers. Results from this approach indicate that the deposit within Kashira crater is best modeled as a combination of surrounding spectral units (i.e., in-scene derived endmembers) with the addition of the kaolin-group mineral halloysite. Linear unmixing of TES data suggest that the deposit contains $30% halloysite, a result that is supported by a sensitivity analysis. Potential formation mechanisms for this deposit include hydrother-mal alteration, arid-environment pedogenic weathering of a basaltic mound deposit, or pedogenic weathering of a volcanic ash deposit. Our modeling results offer a quantitative reconciliation of the CRISM and TES datasets, and provide a consistent mineralogy from spectral unmixing for an aqueous alteration mineral-bearing deposit on Mars using a combined analysis of both VNIR and TIR hyperspectral data. The past decade has seen an influx of hyperspectral visible to near-infrared (VNIR) reflectance data from the surface of Mars measured by the Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument (Bibring et al., 2004) and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument (Murchie et al., 2007). An important discovery enabled by these instruments is the positive identification of a variety of aqueous alteration minerals (e. which support the abundant morphologic evidence that Mars was once a more hydrologically active planet (e. The detections of aqueous phases have been critical in helping to constrain the aqueous history of Mars; however, the majority of VNIR studies of alteration mineral-bearing deposits have been qualitative in nature, focusing on presence/absence detections of unique mineral phases (e. Additionally, thermal infrared (TIR) emissivity data returned from the Thermal Emission Spectrometer (TES) instrument (Christensen et al., 2001) have generally not corroborated the widespread detections of aqueous alteration minerals observed by CRISM and OMEGA (e. Proposed explanations for this discrepancy include low absolute abundances of phyllosilicates, the low spatial resolution of TES (kilometer scale) compared to CRISM (tens of meter scale), and/or the physical effects of …