Thermokarst lakes and ponds on Mars in the very recent (late Amazonian) past

Volcanic terrain and the possible periglacial formation of “excess ice” at the mid-latitudes of Utopia Planitia, Mars

“…Morgenstern et al, 2007;Soare et al, 2007Soare et al, , 2008Lefort et al, 2009;Séjourné et al, 2011Séjourné et al, , 2012. Opinions diverge, however, in response to two questions:…”

“…The suite of putative periglacial-landforms (PPLs) comprises: (a) small-sized (≤50 m) and non-sorted polygonally-patterned ground (Mellon, 1997;Seibert and Kargel, 2001;Morgenstern et al, 2007;Soare et al, 2008Soare et al, , 2012bSoare and Osinski, 2009;Lefort et al, 2009;Levy et al, 2009aLevy et al, , 2009bHauber et al, 2011;Ulrich et al, 2011); (b) multi-metre scale polygon-junction and margin pits (Wan Bun Tseung and Soare, 2006;Morgenstern et al, 2007;Séjourné et al, 2010); and, (c) scalloped depressions that are rimless, flat-floored, metres to decametres deep and metres to kilometres in their long axes (Costard and Kargel, 1995;Morgenstern et al, 2007;Soare et al, 2007Soare et al, , 2008Soare et al, , 2011Lefort et al, 2009;Ulrich et al, 2010;Séjourné et al, 2011Séjourné et al, , 2012.…”

Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE

“…, does not completely rule out the possibility that scallops could be the dry remnants of thermokarst lakes (representing the second major hypothesis for scallop formation; e.g., Soare et al, 2007Soare et al, , 2008Costard and Kargel, 1995). Likewise, the resemblance of several features of terrestrial thermokarst lakes to scallops raises the possibility that liquid water was involved, but does not require it.…”

Widespread crater-related pitted materials on Mars: Further evidence for the role of target volatiles during the impact process

“…These landforms generally form by the removal and/or displacement of some volume of materials. For Mars, these include (1) numerous pristine and degraded impact craters (Craddock et al, 1997;Bleacher et al, 2003;Garvin et al, 2003;, (2) craters produced by primary phreatic and phreatomagmatic explosions (Morris and Mouginis-Mark, 2006;Fagents and Thordarson, 2007;Jaeger et al, 2007;Burr et al, 2009), (3) cratered cone groups and thermokarst terrains produced by interactions between lava flows and nearsurface water and/or ice (Keszthelyi et al, 2008;Burr et al, 2009;Hamilton et al, 2010cHamilton et al, , 2011, (4) devolatilization of pyroclastic density currents (Ghent et al, 2012), (5) collapse pits associated with tectonic structures or drainage of lava lakes/tubes (i.e., pit craters; Okubo and Martel, 1998;Wyrick and Ferrill, 2004;Rowland et al, 2011), (6) mud volcanism (Burr et al, 2009;Skinner and Tanaka, 2007), (7) various ablation and/or sublimation features related to ice-rich terrains, ice-cored mounds, or ice blocks (Lucchitta, 1981;Mustard et al, 2001;Pierce and Crown, 2003;Soare et al, 2007Soare et al, , 2008Kadish et al, 2008;Searls et al, 2008;Burr et al, 2009;Hartmann et al, 2010), and (8) some complex aeolian structures, such as ergs that can develop negative relief features between a high-standing network of star dunes (Edgett and Blumberg, 1994;Bridges et al, 2007;Bourke et al, 2010). Pits or pit-like features formed in each these settings have distinctive morphologic and geologic characteristics and are often confined to a specific geologic setting, such as a volcanic province.…”