Simple Crater Morphometry And Degradation Processes On Mercury From Messenger Stereo Topography

Topographic surface degradation on Mercury is predicted to occur at almost double the rate observed on the Moon, but the exact cause of this enhancement is currently unknown. Impact cratering is thought to play an outsized role in resurfacing on Mercury due to the higher energy impact environment leading to more noticeable effects from secondary processes such as ejecta emplacement, thermal cycling, and seismic shaking. The proposed investigation would use MESSENGER mission data to address this conundrum in Mercury's geologic evolution. Recent advances in topographic processing techniques would provide a more complete picture of crater degradation processes across the critical diameter range of ~0.8-5 km that is most sensitive to the high energy impact environment on Mercury. Our primary objective is to quantify the extent of crater degradation in Mercury's volcanic smooth plains in terms of characteristic diffusivities and erosion rates by comparing observed crater topography to output from a numerical diffusion model. In addition to studying the impact cratering process itself, the size-frequency distribution of these craters will provide an independent constraint on the timing of the last major stage of volcanic activity on Mercury. The proposed investigation would therefore provide better constraints on the characteristic rates of surface degradation that could help us to understand the myriad geologic processes that are potentially unique to Mercury while also advancing NASA's strategic research aims across multiple priority science questions in the areas of impacts, dynamics, and solid body surface processes. The proposed investigation is relevant to the objectives of DDAP to enhance the scientific return of Discovery-class missions by supporting new analyses, approaches, and interpretations of data. We will undertake new analyses and interpretations of MESSENGER MLA and MDIS data using improved topographic processing techniques that have only become available in the time since the MESSENGER mission ended. The proposed investigation will study the degradation of impact craters on Mercury in order to address broader science questions relating to cratering dynamics and the chronology of major geologic events in the inner Solar System. While some comparative analysis with the Moon will be involved, no new analysis of lunar data will be performed.