How, when and where current mass flows in Martian gullies are driven by CO₂ sublimation

Martian gullies resemble water-carved gullies on Earth, yet their present-day activity cannot be explained by water-driven processes. The sublimation of CO₂ has been proposed as an alternative driver for sediment transport, but how this mechanism works remains unknown. Here we combine laboratory experiments of CO₂-driven granular flows under Martian atmospheric pressure with 1D climate simulation modelling to unravel how, where, and when CO₂ can drive present-day gully activity. Our work shows that sublimation of CO₂ ice, under Martian atmospheric conditions can fluidize sediment and creates morphologies similar to those observed on Mars. Furthermore, the modelled climatic and topographic boundary conditions for this process, align with present-day gully activity. These results have implications for the influence of water versus CO₂-driven processes in gully formation and for the interpretation of gully landforms on other planets, as their existence is no longer definitive proof for flowing liquids.

Lonneke Roelofs, Susan J. Conway, Tjalling de Haas, Colin Dundas, Stephen R. Lewis, Jim McElwaine, Kelly Pasquon, Jan Raack, Matthew Sylvest, Manish R. Patel