Global bedrock composition mapping on Mars using THEMIS and TES Data

Introduction: The Mars Global Surveyor Thermal Emission Spectrometer (TES) has a spatial resolution of ~ 3 x 6 km/pixel, with 143 spectral bands between 50-6 µm (~200-1600 cm-1). Previous compositional studies using TES data have been conducted at the multi-pixel (tens to thousands) level [1-6]. At these spatial scales (>30 km), outcrops of bedrock cannot be resolved, therefore surface composition determined previously with TES data was detected from sand-sized particles or a mixture of rocks and fines [e.g., 2]. Infrared images from the Thermal Emission Imaging System (THEMIS) aboard the 2001 Mars Odyssey spacecraft have a spatial resolution of ~100 m/pixel, with 10 spectral bands between 14.9-6.8 µm (~672-1474 cm-1). The higher spatial resolution of THEMIS allows for areally-small regions of bedrock to be resolved. In this work, nighttime temperatures measured with THEMIS are used to locate bedrock surfaces on Mars (see example, Figure 1). Where available, corresponding daytime THEMIS images are converted to emissivity, and are then used to determine the general composition of these bedrock surfaces. Finally, TES data, used together with THEMIS data, can be used to extract a more precise mineralogy. Approach: In this work, " bedrock " is defined as any surface with a thermal inertia >2200 J/m 2 Ks