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Locations and Properties of Ice-Exposing Scarps and New Impact Craters in the Mid-Latitudes of Mars

May 21, 2021

Although ice in the Martian mid-latitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50-61 north and south latitude, and that they are concentrated in and near Milankovi crater in the northern hemisphere and southeast of the Hellas basin in the southern hemisphere. These may represent locations of particularly thick or clean bodies of ice. Pits created by retreat of the scarps represent sublimation-thermokarst landforms that evolve in a manner distinct from other ice-loss landforms on Mars. New impact craters reveal that clean subsurface ice is widespread at middle and high latitudes in both hemispheres at depths less than one meter. Both the depth to ice and the ice content appear to exhibit significant variability over short distances (tens to hundreds of meters). The lowest-latitude exposed ice is near 39 N and is at the edge of a region where impact exposures between 40-50 N are common, consistent with other indications of a high ice content in this area. This lowest-latitude ice may be currently unstable and subliming. Impact craters on lineated valley fill excavate ice blocks that may represent the top of debris-covered glacial ice. Together, these landforms indicate widespread, clean subsurface ice at middle latitudes on Mars. The distribution and properties of this ice could provide information about past climate conditions.