The importance of lake breach floods for valley incision on early Mars

The surface environment of early Mars had an active hydrologic cycle, including flowing liquid water that carved river valleys 1 – 3 and filled lake basins 4 – 6 . Over 200 of these lake basins filled with sufficient water to breach the confining topography 4 , 6 , causing catastrophic flooding and incision of outlet canyons 7 – 10 . Much past work has recognized the local importance of lake breach floods on Mars for rapidly incising large valleys 7 – 12 ; however, on a global scale, valley systems have often been interpreted as recording more persistent fluvial erosion linked to a distributed Martian hydrologic cycle 1 – 3 , 13 – 16 . Here, we demonstrate the global importance of lake breach flooding, and find that it was responsible for eroding at least 24% of the volume of incised valleys on early Mars, despite representing only approximately 3% of total valley length. We conclude that lake breach floods were a major geomorphic process responsible for valley incision on early Mars, which in turn influenced the topographic form of many Martian valley systems and the broader landscape evolution of the cratered highlands. Our results indicate that the importance of lake breach floods should be considered when reconstructing the formative conditions for Martian valley systems. Lake breach flooding rapidly eroded almost a quarter of the volume of incised valleys on early Mars, influencing the topography of the wider Martian landscape.