Former extent of glacier-like forms on Mars

Abstract

This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.icarus.2016.03.006Mars? mid-latitude glacier-like forms (GLFs) have undergone substantial mass loss and recession since a hypothesised last martian glacial maximum (LMGM) stand. To date, there is a lack of knowledge of the nature and timing of the LMGM, the subsequent mass loss and whether this mass loss has been spatially variable. Here, we present the results of a population-scale inventory of recessional GLFs, derived from analysis of 1293 GLFs identified within Context Camera (CTX) imagery, to assess the distribution and controls on GLF recession. A total of 436 GLFs were identified showing strong evidence of recession: 197 in the northern hemisphere and 239 in the southern hemisphere. Relative to their parent populations, recessional GLFs are over-represented in the low latitude belts between 25 and 40o and in areas of high relief, suggesting that these zones exert some control over GLF sensitivity and response to forcing. This analysis is complemented by the reconstruction of the maximum extent and morphology of a specific GLF for which High Resolution Imaging Science Experiment (HiRISE) derived digital elevation data are available. Using Nye?s (Nye, J. F. [1951] Proc. Roy. Soc. Lond, Ser. A-Mat. Phys. Sci, 207, 554-572) perfect plastic approximation of ice flow applied to multiple flow-lines under an optimum yield strength of 22 kPa, we calculate that the reconstructed GLF has lost an area of 6.86 km2 with a corresponding volume loss of 0.31 km3 since the LMGM. Assuming the loss reconstructed at this GLF occurred at all mid-latitude GLFs yields a total planetary ice loss from Mars? GLFs of 135 km3, similar to the current ice volume in the European Alps on Earth.authorsversionPeer reviewe

Glacial and gully erosion on Mars: A terrestrial perspective

“…as detailed in section 1.1. That the present epoch is one of glacial retreat is broadly acknowledged (Brough et al, 2016a). Our results agree with the broad overall picture from this previous work; that a long glacial epoch that comprised several phases of glacial growth was followed by glacial retreat, dominating present conditions.…”

“… GLF, glacier-like-forms -these landforms are the most similar in scale and form to terrestrial valley glaciers (Hubbard et al, 2011;Brough et al, 2016a). They usually originate from large alcoves in escarpments that can be on crater walls, valley walls, or mesas; are laterally confined to a valley/depression; and can extend out onto plains.…”

“…Although hypotheses that such arcuate ridges represent protalus ramparts have been proposed (Whalley and Azizi, 2003), they are widely interpreted as end moraines based on their similarity to moraine ridges on Earth and to arcuate ridges bounding other ice-rich glacier-like forms on Mars (e.g., Milliken et al, 2003;Arfstrom and Hartmann, 2005;Hubbard et al, 2014;Brough et al, 2016a).…”

Mangala Valles, Mars: A reassessment of formation processes based on a new geomorphological and stratigraphic analysis of the geological units

“…The observations at the Phoenix landing site have shown how ice sublimated in about four sols even at higher latitudes (around 66°North) than Mangala Valles when brought to the surface from the shallow underground (Smith et al, 2009). There is no surviving glacier, underground ice, or any other under formation observed at equatorial latitudes between ± 30° (Cutts and Blasius, 1981;Dundas et al, 2014;Brough et al, 2016). Some well-formed glaciers should be observable at the equator in the current cold climate if a source of atmospheric water was available, but there is no reported case.…”

Time will tell: temporal evolution of Martian gullies and palaeoclimatic implications

“…Therefore, we can hardly take into account any local and/or spatial effects on the temporal evolution of gullies. These are, however, prob-ably important as there is a strong latitudinal control on the distribution and orientation of Martian gullies [e.g., Balme et al, 2006;Dickson et al, 2007;Kneissl et al, 2010;Harrison et al, 2015] and LDM and glacial deposits [e.g., Squyres, 1979;Milliken et al, 2003;Head et al, 2003;Souness et al, 2012;Brough et al, 2016]. Moreover, Dickson et al [2015] show that there is a latitudinal control on the interaction between LDM deposition, removal and gully activity.…”