THE ROLE OF FLUVIAL AND SUBGLACIAL EROSION ON THE FORMATION OF THE MARTIAN VALLEYS (Invited Presentation)

Thousands of valley networks dissect the southern highlands of Mars, standing as proof that water once sculpted the Martian surface. The valleys are diverse: Variability in morphology, scale, and landscape integration suggest that different processes were at play in their formation, hinting at a complex climate reality in ancient Mars. Previous geological interpretations largely invoke surface water runoff to explain valley network origin. However, their variability, the presence of puzzling morphologies within some valleys, and the striking similarity to analogues in the high Canadian Arctic opens the door to an interpretation based on glaciofluvial processes.

To investigate valley origin, we performed a global comparative study of valley network morphometry based on statistical intercomparisons, supported and interpreted with models of erosion. We found that valley formation involved rivers, glaciers, sapping processes, and subglacial meltwater channels, but that subglacial and fluvial erosion are the predominant mechanisms. The subglacial interpretation is further supported by geomorphological comparisons to terrestrial analogues in Devon and Axel Heiberg Islands (Canadian Arctic Archipelago). The inference of subglacial channels among the valley networks supports the presence of ice sheets in the southern highlands during the time of valley network emplacement. Although valley networks interpreted as subglacial are spread among the highlands, the circum-Argyre region displays particularly high densities of these systems.