Crater mound formation by wind erosion on Mars

TL;DR

This study uses mesoscale simulations to explore how wind erosion shapes sedimentary mounds in Martian craters, revealing how crater size and wind patterns influence mound morphology and formation processes.

Contribution

It provides new insights into the formation and evolution of Martian sedimentary mounds through detailed mesoscale modeling of wind erosion effects.

Findings

Peak erosion occurs at ~2 km crater depth.

Smaller craters produce squat mounds, larger craters produce steeper mounds.

Wind stress causes mounds to appear to move upwind, forming 'bat-wing' shapes.

Abstract

Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different crater and mound morphologies to understand the formation of sedimentary mounds. As crater depth increases, slope winds produce increased erosion near the base of the crater wall, forming mounds. Peak erosion rates occur when the crater depth is ~2 km. Mound evolution depends on the size of the host crater. In smaller craters mounds preferentially erode at the top, becoming more squat, while in larger craters mounds become steeper-sided. This agrees with observations where smaller craters tend to have proportionally shorter mounds, and larger craters have mounds encircled by moats. If a large-scale sedimentary layer blankets a crater, then as the layer recedes across the crater it will erode more towards the edges of the crater, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting crater is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to `march upwind' over time, and forming a `bat-wing' shape, as is observed for Mt. Sharp in Gale crater.