Barnard Crater, Mars: Evidence of Glaciofluvial Activity in a Large, High-latitude Impact Crater in Southern Hellas

Abstract Barnard, a 121.1 km diameter crater along the southern rim of Hellas basin, is a well-preserved complex crater with a history of burial, excavation, and fluvial/glacial activity on its floor and walls. The interior of Barnard shows ice-rich deposits similar to other mid-to-high-latitude craters on Mars but is distinctive in that it also contains sinuous ridges. We have completed a geologic map of Barnard and surrounding materials using the global CTX mosaic. Mapping has identified and shown the distribution of features including sinuous ridges and fluvial channels, attributed to subglacial melting, and lobate debris aprons, mantling deposits, and arcuate ridges, indicative of the deposition and mobilization of ice within the crater. We have identified 13 geologic units on and around Barnard, including three distinct floor units, suggesting sustained periods of infill. We have conducted topographic and morphometric analyses using MOLA and HiRISE DTMs across Barnard and its interior landforms, which show significant infill on the crater floor (∼1 km thick), and local excavation of floor deposits indicating continued modification. Lobate debris aprons extending from the crater walls have maximum thicknesses of ∼300–350 m. Sinuous ridges on the crater floor range in height from ∼10 to 20 m. Crater counts on Barnard’s ejecta show that it formed ∼3.81 Ga in the Middle to Late Noachian, with subsequent periods of infill, excavation, fluvial, and wet-based glacial activity modifying its interior during the Late Hesperian/Early Amazonian, followed by further deposition and flow of ice-rich materials between ∼400 and 16 Ma into the Late Amazonian.