Aeolian processes on Mars: atmospheric modeling and GIS analysis

Abstract

Wind is currently the dominant geological agent acting on the surface of Mars. A study of Martian aeolian activity leads to an understanding of the forces that have sculpted the planet's face over the past billion years or more and to the potential discovery of climate shifts recorded in surface wind features that reflect ancient wind patterns. This work takes advantage of newly available tools and data to reconstruct the sedimentary history reflected in aeolian features on Mars. The thesis is divided into two main projects. In the first section, a widely accepted hypothesis, that oscillations in Martian orbital parameters influence atmospheric circulation patterns, is challenged. A Mars global circulation model is run at different obliquity, eccentricity, and perihelion states and the predicted surface wind orientations are correlated with observed aeolian features on the Martian surface. The model indicates that orbital parameters have little effect on wind patterns, suggesting that aeolian features not aligned with the current wind regime must have formed under atmospheric conditions unrelated to orbital parameters. In the second project, new spacecraft data and a mesoscale model are used to determine the sedimentary history of Proctor Crater, a 150 km diameter crater in the southern highlands of Mars. Using high-resolution imagery, topography, composition, and thermal information, a GIS was constructed to study the aeolian history of the crater, which was found to have a complex interaction of deposition and erosion. Surficial features include 450 m of sediments filling the crater basin, small bright bedforms, dust devil tracks, and a dark dunefield consisting of coarse, basaltic sand and containing slipfaces indicative of a multidirectional, convergent wind regime. All wind features, both ancient and contemporary, are coaligned, indicating that formative wind directions have changed little since the first aeolian features formed in this area. Mesoscale model runs over Proctor Crater indicate that two dune slipfaces are created by winter afternoon geostrophic westerlies and summer evening katabatic easterlies, and that dust devil tracks are created by summer noontime rotational westerlies. Using all available tools, this thesis begins the work of understanding how aeolian processes have influenced the Martian surface.