Search

Paleolake deposits offer a valuable record for constraining ancient Martian environments and climate. Gale crater provides extensive evidence for a long and complex history of lakes; however, the exact timing, source of water, and climate under which these large lakes persisted are still unclear. We examined the geomorphology and mineralogy of Garu crater, an ∼30 km diameter crater ∼150 km to the east of Gale crater with an age of ∼3.5 Ga (Hesperian). Garu hosts a large NE‐prograding sedimentary deposit that emanates from an incised bedrock canyon. Based on detailed geomorphic analysis, we infer it to be a Gilbert‐type delta that records steadily rising water levels over 104–105 years. This aggradational stage is followed by a period of rapid desiccation, which is evidenced by a lack of post‐depositional incision into the delta. Coupled surficial and groundwater modeling and paleo‐flow analysis suggest that the highest mapped lake stand in Garu would have been coeval with one of the largest late‐stage lakes in Gale. Both lake stands would have been supported by groundwater and surface runoff, under a semiarid climate. Unlike Gale, there is no spectral evidence for salts in Garu, which suggests that lacustrine sedimentation in Garu occurred after the deposition of the sulfate layers within Gale's central sedimentary mound. The hydrogeomorphologic record of Garu crater suggests that the climatic conditions that allowed for late Hesperian lakes in Gale crater were not isolated, and other nearby craters and basins may have responded to similar forcings from a regionally integrated hydrologic system. Plain Language Summary: Although Mars is currently cold and dry, and unable to host liquid water, a number of features on its surface tell us that Mars was once a much wetter place. Some of the best indicators that Mars was able to host abundant liquid water in its past are ancient crater lakes, which are often identified by the presence of deltas, river‐cut canyons, and water‐altered sediments. Here we investigate one of these lakes in detail, located in Garu crater, which is ∼150 km east of Gale crater, home of the NASA Curiosity rover. Using a combination of satellite imagery and topographic maps, we show that the lake in Garu steadily rose over 10,000 to 100,000 years, building a delta as sediment was transported from a large canyon into the lake. Prior modeling suggests that almost half of the water was derived from groundwater, which is consistent with our paleo‐surface‐hydrology calculations, and that the same groundwater table that fed Garu also fed Gale crater. Garu is further evidence that the climate that allowed for large lakes in Gale crater also allowed for other large lakes in the region, and that these lakes were interconnected. Key Points: The Garu crater lake was coeval with a large late‐stage lake in Gale crater, and both lakes were supported by the same groundwater system under a semiarid climateLake sedimentation in Garu likely occurred after deposition of the sulfate‐rich layers within Gale's sedimentary mound between ∼3.5 and ∼3.3 GaThe hydrogeomorphologic record of Garu crater suggests that the climatic conditions that allowed for late Hesperian lakes in Gale crater were not isolated [ABSTRACT FROM AUTHOR]