Constraining the formation mechanism of geologic depressions on the surface of Mars can shed light on the planet’s climatic, hydrological, and geochemical evolution. At Osuga Valles, surface morphologies indicative of catastrophic flood events can be tracked from their chaotic origins down to their sink at terminal depressions, or cavi. The channel-cavi association suggests a genetic link between inflowing floodwater and cavi formation and evolution. The geologic settings are consistent with a Hesperian-aged pre-flood, evaporite-containing sedimentary basin. Estimated water volumes associated with the Osuga Valles floods suggest cavi formation within this sediment-filled basin by surface collapse into voids generated by dissolution of subsurface salts, most likely magnesium sulfate minerals, which were previously detected in the region. Geologic mapping reveals that initial cavi collapse was associated with relatively low-discharge floods of Middle Amazonian age, which likely infiltrated the subsurface through fractures. Subsequent higher-discharge floods drained directly into the evolving cavi, causing further dissolution and collapse. Terminal depressions at the end of channel systems on Mars may be related to inflowing floodwater and the remobilization of magnesium sulfates within a pre-existing sedimentary basin, according to remote sensing observations and digital terrain mapping.
Naor et al. (Sat,) studied this question.