Thermal infrared data analyses of Meteor Crater, Arizona: Implications for Mars spaceborne data from the Thermal Emission Imaging System

Thermal infrared (TIR) data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument are used to identify the lithologic distribution of the Meteor Crater ejecta blanket and nearby (within ~3 km) region. This has many applications to the analysis of data from the Thermal Emission Imaging System (THEMIS) instrument that is currently in orbit at Mars. ASTER and THEMIS, whereas orbiting different planets, have similar spatial and spectral resolutions. THEMIS represents the highest spatial resolution (100 m) to date of the Martian surface, thereby allowing small (~ 1km) impact craters to be studied in detail for the first time. Meteor Crater serves as an analog for the many similar-sized impact sites on the surface of Mars. These sites are future research targets with THEMIS, and ASTER data of Meteor Crater provides ideal data and geologic landscape in preparation for future THEMIS investigations. Fieldwork at Meteor Crater yielded sample collection of the primary lithologies and an opportunity to validate previously-collected high-resolution (3.2 m), airborne Thermal Imaging Multispectral Scanner (TIMS) data. Laboratory thermal emission spectra were obtained for the samples collected. Deconvolution of ASTER TIR emissivity data were performed with image end-members and sample end-members. Comparisons of the spaceborne data to high-resolution airborne TIMS data were used to assess the validity of the ASTER end-member analyses. The ASTER image end-member analysis agreed well with the earlier TIMS end-member analysis where the effects of resolution degradation were accounted for. Laboratory spectra and mineral spectral libraries provided poor fits of deconvolution of multispectral TIR data. Lithologies with similar spectral signatures or with low areal abundances were difficult to identify.Using the same methodology as that applied to the ASTER TIR data of Meteor Crater, THEMIS TIR data of a small (~ 1 km) impact crater in Syrtis Major were analyzed. The crater's rim and ejecta blanket was found to contain larger particle sizes than the surrounding (ejecta-free) plain, indicating a young (fresh) impact age and little or no accumulation of dust. The composition of the rim, ejecta, and surrounding plain was determined to be basaltic. It is hoped that the work performed here will complement future investigations of fresh impact sites with THEMIS data that may be used to solve geologic questions such as 1.) the composition of ejecta blocks that represent pre-impact, underlying stratigraphy in high-albedo, dust-covered regions of Mars, 2.) the approximate age of impact, and 3.) regolith/dust thickness, which appears to be a factor of #2