MORPHOLOGY OF CRATERS WITH ALLUVIAL FANS IN TERRA SABAEA, MARS

A small percentage of Martian impact craters contain alluvial fans; sedimentary depositional features caused by fluvial transport and identified by their conical shaped layered deposits and source alcoves. Craters with alluvial fans generally occur in three specific regional areas and their pattern of formation is not well understood. For example, it is unclear why alluvial fans occur in certain craters and not others with similar size, type, and morphological characteristics. The large alluvial fans appear to form exclusively within the crater rims, so the process may be linked to the cratering process itself.

This research focuses on Terra Sabaea, where 7 impact craters contain alluvial fans, as identified by Moore and Howard (2005). We analyzed the crater morphology of two groups of craters in this region; those modified by alluvial fans and those not modified by alluvial fans. Using the crater characteristics reported in Robbins and Hynek (2012) database, we compared the two groups. In addition, we compared the crater rim curvature between the two groups by selecting representative craters and extracting eight elevation profiles using gridded MOLA topography. We calculated the curvature of the crater rims using two different approaches. The first method, outlined in Moore and Howard (2005) and Kraal et al. (2008), describes how concave or convex the profile of the crater is. The second method, used by Mangold et al. (2012), describes the geometric shape of the crater rim by comparing the rim slope to the overall crater diameter and shape. We will compare our crater characteristic results for Terra Sabea to those published for Margaritifer Terra and Tyrrhena Terra (Mangold, et al. 2012).