Widespread Exposures of Extensive Clean Shallow Ice in the Mid-Latitudes of Mars

• Published in: Journal of Geophysical Research: Planets
• Main Authors: Dundas, Colin, Mellon, Michael, Conway, Susan, Daubar, Ingrid, Williams, Kaj, Ojha, Lujendra, Wray, James, Bramson, Ali, Byrne, Shane, McEwen, Alfred, Posiolova, Liliya, Speth, Gunnar, Viola, Donna, Landis, Margaret, Morgan, Gareth, Pathare, Asmin
• Other Authors: US Geological Survey Flagstaff, United States Geological Survey Reston (USGS), Laboratoire de Planétologie et Géodynamique UMR 6112 (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; Thermokarst
• Online Access: https://hal.archives-ouvertes.fr/hal-03186594; https://hal.archives-ouvertes.fr/hal-03186594/document; https://hal.archives-ouvertes.fr/hal-03186594/file/Dundas_etal_ice_exposures_v11_revised5_4HAL.pdf; https://doi.org/10.1029/2020JE006617

International audience Although ice in the Martian midlatitudes 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° and 61° north and south latitude and that they are concentrated in and near Milankovič 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 1 m. Both the depth to ice and the ice content appear to exhibit significant variability over 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° and 50°N are common, consistent with other indications of a high ice content. 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.