Martian Dune Fields: Aeolian Activity, Morphology, Sediment Pathways, and Provenance

Wind has likely been the dominant geologic agent for most of Mars’ history. The wide-spread nature of sand dunes there shows that near-surface winds have commonly interacted with plentiful mobile sediments. Early studies of these dunes suggested minimal activity, dominantly unidirectional simple dune morphologies, and little variations in basaltic sand compositions. This dissertation examines martian sand dunes and aeolian systems, in terms of their activity, morphologies, thermophysical properties, sand compositions, geologic contexts, and source-lithologies using new higher-resolution orbital data. Although previous evidence for contemporary dune activity has been limited, results presented in Chapter II show substantial activity in Endeavour Crater, Meridiani Planum. The translation and erosion of dunes there constitutes the largest contemporary movement of sand-sized sediment reported on Mars to date and demonstrates that Endeavour crater has been subject to wind profiles exceeding the threshold velocity at the surface (daily/seasonally and/or episodically) in the recent past. Global mapping has shown dune fields to dominantly occur in topographically benign locations (e.g., craters, polar basins), where the largest exception is the Valles Marineris (VM) rift system. Chapter III documents multiple occurrences of “wall dunes” found several kilometers above the canyon floor. These relatively unique dune morphologies show that wind blown sediment has interacted with local and regional topography and are relevant for understanding aeolian sediment flux, sediment sources, and wind directions. Chapter IV provides results of a low- to mid-latitude survey of all martian dune fields in comparison to the extensive dune population in VM to test the effect of local and regional environments on duneform properties. That study found VM dune fields to be qualitatively and quantitatively distinct from other dune populations, most readily attributed to the rift’s unusual setting. Sources and pathways of the martian sand have largely been uncertain. Chapter V documents likely sediment sources and pathways for the VM dune populations, where local and regional derivation of dune sand has occurred. We find in some chasmata dune sand is dominantly derived from Noachian-aged (altered and unaltered) igneous wall materials, whereas in other chasmata dunes are sourced from Early Hesperian-aged sulfate-bearing sedimentary layered deposits.