A Method for Identifying Mineralogical Signatures in Locales With Large Topography Using Atmospherically Equalized THEMIS Data

We have developed a method for using THEMIS data to study the mineralogy of surfaces that have large elevation changes, such as the unusual blocky terrain in Melas Chasma, in order to identify locales of mineralogical interest. Surfaces with large topography are commonly difficult to interpret using THEMIS data alone because atmospheric transmittance typically dominates the observed radiance. Fortunately, there is a quasi-linear relationship between topography and transmittance, allowing the quasi-linear effect of transmittance to be characterized and removed, and the mineralogy of surfaces identified. We illustrate the use of the quasi-linear relationship between elevation and transmittance to create real-time atmospheric corrections for THEMIS data, demonstrating the technique at the Valles Marineris and globally. Initial results allow us to identify and mineralogically characterize small outcrops using the high spatial resolution THEMIS data in and around the Valles Marineris, as well as other regions with large topography on Mars.