High‐resolution thermal inertia derived from the Thermal Emission Imaging System (THEMIS): Thermal model and applications

Abstract

Thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the Thermal Emission Imaging System (THEMIS) on the Mars Odyssey spacecraft, producing the highest‐resolution thermal inertia data set to date. THEMIS thermal inertia values have an overall accuracy of ∼20%, a precision of 10–15%, and are consistent with both Thermal Emission Spectrometer orbital and Miniature Thermal Emission Spectrometer surface thermal inertia values. This data set enables the improved quantification of fine‐scale surface details observed in high‐resolution visible images. In the Tharsis region, surface textures and crater rims observed in visible images have no corresponding variation in the THEMIS thermal inertia images, indicating that the dust mantle is pervasive at THEMIS scales and is a minimum of a few centimeters and up to 1–2 m thick. The thermal inertia of bed form material indicates particle diameters expected for aeolian sediments, and these materials are likely currently saltating. Variations in the thermal inertia within interior layered deposits in Hebes Chasma can be distinguished, and the thermal inertia is too low to be consistent with bedrock or a lava flow. Thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation. Higher‐resolution THEMIS thermal inertia enables the identification of exposed bedrock on the Martian surface. In Nili Patera and Ares Vallis, bedrock material corresponds to distinct compositional and morphologic surfaces, indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes.