Scour Pits in the Medusae Fossae Formation and Olympus Mons Region on Mars

Abstract

The Medusae Fossae Formation (MFF) covers a region of Mars located to the southwest of the Olympus Mons shield volcano. The nature of this formation has been under debate for over 30 years. In order to better understand the MFF, we investigated scour pits or V-shaped depressions carved into many places across the MFF. We quantified the number and distribution of the scour pits, their length, width, and orientation, and classified them into distinct morphologies: central peak-scour pits, barchan-shaped scour pits, and asymmetric scour pits. We hypothesize that scour pits initially develop as central peak scour pits when wind carves the area around a more resistant obstacle. Therefore, the orientation of the scour pit reflects the orientation of the formative winds. In this study, we found that scour pits in the MFF have similar orientations and morphologies to scour pits found in the north, west, and southwestern flanks of Olympus Mons. These similarities suggest that the scour pits in the MFF and around Olympus Mons are carved into similar materials. We propose that the MFF material extends up to the Olympus Mons region, leading to more MFF material exposed near Olympus Mons than previously mapped. The distribution of scour pits and proximity to Olympus Mons supports previous interpretations that the MFF is pyroclastic in origin.