MARTIAN STEPPED FANS RECORD RAPID WATER RELEASE

Martian stepped fans have a distinctive terraced profile. Using flume experiments, we find that distinct terraces form as a fan deposits into a crater basin filling with water. Terrace preservation implies no long-term deposition at a stable water level and an inactive fluvial system during water drainage. Based on scaling from our experiments, we estimate that the formation time for Martian stepped-fans is on the order of decades and conclude that stepped fans on Mars likely formed during a single, basin-filling event driven by a short-lived, intense hydrologic cycle. The estimated discharge rates are comparable to some of the largest rivers on Earth and these rates highlight the challenges of determining the water source.