Noachian Proglacial Paleolakes on Mars: Regionally Recurrent Fluvial Activity and Lake Formation within Closed-source Drainage Basin Craters

A body of geologic evidence suggests that Noachian-aged craters on Mars were modified primarily by runoff from rainfall in a warm and wet early Mars climate. Although melting and runoff of frozen water ice have been suggested as plausible alternatives, supporting geomorphic evidence of Noachian glaciation on Mars has been elusive. We previously identified a Noachian-aged crater in the southern highlands that contained evidence of glacially derived fluvial and lacustrine features but was hydrologically disconnected from its surroundings. This closed-source drainage basin (CSDB) crater and proglacial paleolake provided the first candidate evidence of Noachian cold-based glaciation on Mars. Here, we describe a second nearby CSDB crater that contains similar evidence of glacial melting leading to the formation of proglacial fluvial channels and paleolakes on the crater floor. This new evidence suggests that CSDB formation was occurring episodically at regional scales throughout the Late Noachian and into the Early Hesperian. Recurrent episodes of glacial melting are consistent with climate model predictions of a cold and icy early Mars highlands with limited melting of glacial ice during periods of punctuated warming.