Impact Induced Landslides as a Mechanism for Diffusive Degradation of Complex Craters found Near the Lunar Southern Pole

Abstract

Throughout its history, the Moon’s surface has experienced numerous impact cratering events. Such events have degraded the surface through various processes. Processes include ejecta blanketing, overlapping (cookie cutting), and topographic diffusion. Ejecta blanketing is the process of impact ejecta from other craters covering or partially covering pre-existing craters with their ejecta, degrading crisp topographic features and morphologies. Overlapping, or cookie cutting, is the process in which pre-existing craters have craters from other impactors partially or completely overlap them. Finally, there is topographic diffusion. Topographic diffusion is the dispersal of the lunar regolith through impact events near and overlying pre-existing craters. This study discusses impact driven landslides on crater walls as a key degradation mechanism by considering 16 complex craters around the southern pole of the Moon. By using crater counting, statistical analysis is completed on the crater size populations found on these complex craters’ walls, which have varying slope conditions. The results show that the crater populations ranging from 600-800 m diameter are significantly lacking on the walls. It is proposed here that this is likely due to landslide events that cause partial or total erasure of the crater cavities in that size range. Additional analysis of complex crater degradation rate by incorporating the 2014 diffusive model proposed by Fassett and Thomson confirms this interpretation. This diffusive model has been used with success in the study of smaller, simple craters but has not been investigated as a mechanism for degradation of complex craters until now.