The surface environment of early Mars had an active hydrologic cycle, including flowing liquid water that carved river valleys^1,2,3 and filled lake basins^4,5,6. 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^7,8,9,10. Much past work has recognized the local importance of lake breach floods on Mars for rapidly incising large valleys^{7,8,9,10,11,12}; however, on a global scale, valley systems have often been interpreted as recording more persistent fluvial erosion linked to a distributed Martian hydrologic cycle^{1,2,3,13,14,15,16}. 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.

早期火星的地表环境有一个活跃的水文循环，包括流动的液态水，形成河谷^1,2,3并充满湖盆^4,5,6。这些湖盆中有 200 多个充满了足够的水来突破限制地形^4,6，导致了灾难性的洪水和出口峡谷的切割^7,8,9,10。许多过去的工作已经认识到火星上湖泊决口洪水对迅速切割大山谷的局部重要性^{7,8,9,10,11,12}；然而，在全球范围内，山谷系统通常被解释为记录了与分布式火星水文循环相关的更持久的河流侵蚀^{1,2,3,13,14,15,16}. 在这里，我们展示了湖泊破裂洪水的全球重要性，并发现它至少侵蚀了火星早期切割山谷体积的 24%，尽管仅占山谷总长度的大约 3%。我们得出的结论是，湖泊决口洪水是造成火星早期山谷切割的主要地貌过程，这反过来又影响了许多火星山谷系统的地形形态和陨石坑高地的更广泛的景观演变。我们的结果表明，在重建火星河谷系统的形成条件时，应考虑湖泊决口洪水的重要性。