Martian landscapes of fluvial ridges carved from ancient sedimentary basin fill

Large sedimentary basins contain archives of Earth history. It is unknown to what extent similar basins existed on Mars because there are few observations relating to the subsurface and it is difficult to identify buried deposits. Here, we used numerical simulations to show that landscapes of networks of topographic ridges that are abundant on the surface of Mars may represent erosional windows into thick, basin-filling river deposits that accumulated over long time spans. We used a numerical model to drive hillslope creep and differential erosion from the wind to simulate Mars-like exhumation processes acting on basin-filling fluvial strata, which we based on those buried in the Gulf of Mexico on Earth, as imaged using three-dimensional reflectance seismology. Simulations produced remarkably Martian landscapes in which the preferential erosion of mudstone relative to sandstone channel belts leads to the development of complex patterns of intersecting ridges. Our findings contrast to the existing view of ridged Martian landscapes as thin-skinned surface deposits preserving fluvial landscapes at a snapshot in time. Instead, the ridge cross-cutting patterns produced by the model reflect the exhumation of channel bodies at different stratigraphic levels, exposing basin strata accumulated over time scales of 500,000 years. Thus, we propose that fluvial ridges on Mars may expose an archive of long-lived aqueous processes.