SAND DEPOSIT MAPPING AND AEOLIAN MORPHOLOGIES AS CLUES FOR IDENTIFYING ORIGINS OF DARK SAND IN AEOLIS DORSA, MARS

Dark sand deposits occur at all latitudes on the Martian surface. Sand sources in some regions have been inferred via paleo-wind indicator analyses, sand and source mineralogy comparisons, and climate modeling. However, all known sources are sedimentary, leaving outstanding the question of primary igneous origin(s) of these dark sand deposits. One hypothesis addressing this question is that volcaniclastic deposits are a primary origin of Martian sand. Terrestrial analogs of volcaniclastic units sourcing sand support this hypothesis. However, sand generation has yet to be observed or inferred from any such Martian deposit. This thesis tests this hypothesis via a case study in Aeolis Dorsa, Mars, a locality where sand overlies bedrock consisting of a hypothesized volcaniclastic deposit, the Medusae Fossae Formation (MFF). In addition to the MFF, additional potential external sand sources exist: Elysium Mons, the Cerberus Plains lavas, and the Southern Highlands.To identify likely sand source(s) in Aeolis Dorsa, sand deposits were mapped to address geospatial sand distribution, scour mark orientations were mapped and analyzed to reveal dominant paleo-wind directions, and instances of apparent erosion of bedrock to dark sediment were recorded. Hierarchical clustering analysis of sand distribution revealed preferential sand deposition on the peripheries of the MFF and in the southern depression (where bedrock may be remnant southern highlands material). Hierarchical cluster analysis of scour mark distribution revealed spatial groups of scour marks with consistent paleo-wind directions within groups. Such paleo-wind directions provide no evidence for long-distance sand transport from potential external source regions, but instead provide support for paleo-winds controlled by local topography. Apparent erosion of bedrock to dark sediments occurs in both the MFF (in ~20 localities) and in the southern depression (in over 100 localities), suggesting that both the MFF and bedrock in the southern depression have the potential to generate dark sand. The implication that the MFF has the potential to produce dark sand raises two important possibilities: first, that elsewhere along the Martian equator the MFF may have produced dark sand, and second, that other friable layered deposits (of which the MFF is one) may also serve as sources of Martian sand