Analysis of surface compositions in the Oxia Palus region on Mars from Mars Global Surveyor Thermal Emission Spectrometer Observations

We examine the distribution of Thermal Emission Spectrometer (TES) derived surface compositions in the Oxia Palus region on Mars through high-spatial-resolution mapping and integration with Mars Orbiter Camera and Mars Orbiter Laser Altimeter data sets. We also fit the basalt and andesite-weathered basalt interpretations of TES surface type 1 and type 2 materials into multiple working hypotheses to describe the origin of surface compositions. A mixing/transition from surface type 1 to type 2 is observed in low-albedo regions of southern Acidalia Planitia and may represent either (1) an influx of basaltic sediment from the southern highlands, deposited on and mixed with andesitic volcanics; (2) an influx of water-transported basaltic sediment from the southern highlands that was altered and later deposited as a thin sedimentary veneer; or (3) different degrees of weathering of indigenous basalt, marking the geographic extent of submarine alteration of basaltic crust. TES spectra of low-albedo intracrater materials reveal that surface type 1 compositions form a central core on crater floors, while type 2 compositions form a surrounding arc on the dark downwind sides of crater walls. Intracrater floor materials are interpreted as eolian sediment, and wall materials are interpreted as either eolian sediment or eroded material from in-place crater wall lithologies. Surface type 1 and type 2 compositions are also observed in adjacent low-albedo wind streaks; however, a mixing trend is not as evident. The Mars Pathfinder landing site and Ares and Tiu Valles source regions are sufficiently blanketed by fine-grained dust to prohibit the analysis of surface rock compositions.