Constraining weathering processes from particle size distributions and Magellan Synthetic Aperture Radar (SAR)

Due to Venus' unique surface conditions the processes controlling the distribution of impact crater ejecta and sediment transport occurring on this planet are different to those on the Earth. Venus' dense atmosphere acts to remove or reduce small meteors during atmospheric entry, resulting in a lack of small impact craters on the surface. Ejecta dispersal from large impacts, where the meteor was able to survive the transit through the dense atmosphere of Venus, are unconstrained. Sediment transport and the influence of the dense and sluggish atmosphere on the surface are also poorly constrained. Our study aims to investigate the processes responsible for the distribution and deposition of ejecta at large parabolic impact craters on Venus. From this we aim to constrain the near surface-atmospheric processes responsible for sediment transport on Venus. Large parabolic impact craters were chosen since their westward orientated ejecta blankets could suggest deposition by Venus' east-west orientated zonal winds, allowing us to investigate the atmospheric effects on crater ejecta dispersal. We use Synthetic Aperture Radar (SAR), obtained from the Magellan mission to Venus, to study the Fresnel reflectivity and emissivity of ejecta blankets at selected sites on Venus. The particle size distribution associated with the ejecta of parabolic impact craters are dependent on the particle size, crater radius, radial distance from the center of the crater and an empirical power law coefficient. By combining reflectivity with particle size distributions we can constrain the surface-atmosphere processes acting to produce small-scale roughness and topography variations, and weathering processes on Venus.