Possible ice-wedge polygons and recent landscape modification by “wet” periglacial processes in and around the Argyre impact basin, Mars

• Published in: Icarus
• Main Authors: Soare, R. J., Conway, S. J., Dohm, J. M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2014
• Subjects: Ice; permafrost; wedge*
• Online Access: https://oro.open.ac.uk/39636/; https://oro.open.ac.uk/39636/1/Soare_conway_dohm_2014.pdf; http://www.sciencedirect.com/science/article/pii/S0019103514000657; https://doi.org/10.1016/j.icarus.2014.01.034

The Argyre basin and associated rim-materials in the southern hemisphere of Mars are ancient, having been formed by the impact of a large body ~4 Gya. This notwithstanding, the regional landscape continues to be altered by a multiplicity of geological and geomorphological processes. Three landforms, whose close spatial-association is identified in a new geological map of the Argyre region (~290–360°E; ~30–72°S), feature prominently in the list of very Late Amazonian Epoch alterations: (a) Small-sized (≤~20 m in diameter) and unsorted polygons that exhibit metre to sub-metre elevated margins or shoulders, giving them a low-centred appearance; in “wet” permafrost environments on Earth low-centred polygons (LCPs) often are underlain by ice-wedges. (b) Gullies, seemingly formed by “wet” flow(s) and incised by the LCPs. (c) A putative (possibly ice-rich) latitude-dependent mantle (LDM) that underlies the LCPs and spatially-convergent “wet” gullies in all of our observations. These landforms occur from the middle to the high (near-polar) latitudes of the region and overlie geological units of all ages. Hitherto, the presence of the LCPs has been reported only fleetingly in the literature and only in as much as they have been observed on the walls of a few scalloped depressions in mid-Utopia Planitia. By contrast, we report the ubiquitous occurrence of the LCPs in and around the Argyre impact-basin on gully-margins and adjacent slopes as well as on relatively-flat inter-crater terrain. On the basis of three separate but related lines of reasoning we hypothesise that ice wedges could be present beneath LCP margins in our study region. If we are correct then these LCP sites are geomorphological expressions of boundary conditions that were relatively warm and wet in the recent past. First, substantial ice-wedging in permafrost environments on Earth requires the availability of meltwater. If, as some researchers propose, the formation of some “wet” gullies at the martian mid-latitudes is induced by the localised ...