Using Remote Sensing Techniques to Assess the Geologic Context of Olivine-Bearing Materials within Terra Sirenum, Mars

Understanding olivine-bearing materials in Terra Sirenum provides insight into the magmatic and hydrologic processes that shaped the Southern Highlands of Mars. Our study addresses two questions: "What is the geologic context of olivine compositions in the study area?" and "What does olivine abundance, composition, and geologic context suggest about the magmatic and weathering processes in our study area?" To answer these questions, we mapped olivine deposits within a region of Terra Sirenum using JMARS [1]. We used Thermal Emission Imaging System (THEMIS) data to map the extent of olivine deposits and to understand their degree of consolidation. To investigate olivine composition, we used the Thermal Emission Spectrometer (TES) global maps of Forsterite/Fayalite compositions [2]. We found that the olivine compositions vary from most iron-rich types (Fo01) to the most magnesium-rich (Fo91), with the vast majority identified as Fo68. The results of our study are consistent with those implied by the magma overturn model [3], which explains the compositional changes in Martian magmas over time. In addition, the extent of olivine-bearing deposits within our study area suggests that mechanical weathering (e.g., aeolian and gravity-driven processes) is more likely to dominate the sedimentary record in recent geologic time over water-driven processes. We will present our results, which detail the present-day surface geology of our study area in Terra Sirenum. Our results have implications for Martian magma evolution as well as the extent water has played in shaping the surface of the planet. [1] Gorelick, N., et al. (2003), Lunar and Planetary Science, XXXIV. [2] Koeppen, W.C., et al. (2008), Journal of Geophysical Research, 113, E002984. [3] Elkins-Tanton, L.T., et al. (2003), Meteorites & Planetary Science, 38, tb00013.