Martian canyon scoured by upslope winds

Mount Sharp in Gale crater on Mars is the eroded remnant of a formerly more extensive mass of sedimentary rocks. What is the mechanism by which wind erosion scours mountains on Mars? Within canyons on Mount Sharp, the Mars Science Laboratory Curiosity rover has found residual bedrock tails, behind erosion-resistant obstacles such as nodules and fins. These residual bedrock tails record rock erosion by sediments transported by slope winds. At Marker Band Valley, the orientation of bedrock tails indicates scouring by upslope winds. Such upslope scouring is in contrast to that of mountains on Earth, which are eroded principally by the action of fluids moving downslope. However, this result is consistent with the predictions of numerical models that the canyon was scoured during the daytime when strong upslope winds are expected. Inferred scarp recession rate averaged over the past 10 Myr is ~3 μm/year, probably too slow to explain the formation of Mount Sharp unless erosion was faster in the past. The abraded material is likely ultimately removed from Mount Sharp by suspension, rather than being redeposited locally.