Speaker: Dr. Anna Grau Galofre
Title: "Valley network formation under ancient Martian ice sheets"
Abstract: Thousands of ancient valleys incise the southern hemispheric highlands of Mars, standing as proof that liquid water once flowed on the surface of the planet. Due to their striking similarity to river networks, the Martian valleys have historically been interpreted as fluvial runoff systems that formed under a warmer and wetter climate. However, many aspects of valley morphology are hard to reconcile with fluvial erosion, such as sections of uphill flowing along-valley profiles, lack of inner channels, lack of intervalley dissection, and channels that disappear and reappear. Whereas these characteristics are puzzling, they are common in channel systems originated under ice sheets, operating as pressurized meltwater drainage conduits. Over extensive field studies, me and my collaborators have mapped subglacial channel networks formed under the former reaches of the Devon and Stacie ice caps (Canadian high Arctic), and found analogues to many of the morphologies typical of Martian valley networks. The subglacial environment, particularly which related to locally wet ice sheets, may provide a plausible explanation for the formation, distribution, and puzzling morphology of a considerable number of valley networks, and help reconcile the long-term paradox concerning geological observations and climate models for early Mars.