Radar and Geomorphic Evidence of the Occurrence of Massive Ground Ice in the Martian Northern Plains
Abstract
The possibility that a large ocean or massive ice-sheet once occupied the Martian northern plains has been proposed based on the interpretive identification of various landforms, including sedimentary deposits [1, 2], outwash plains [3] and possible paleoshorelines - the latter based largely on the work of Parker et al. [4-7], who identified evidence of a series of nested levels, which they interpreted as shorelines, located along the highland/lowland boundary. The combination of high-resolution orbiter images with MOLA gridded topography has enabled the compilation of regional and global maps of the proposed shorelines. The highest and oldest of these is called the 'Arabian Level' and is believed to date back to the Late Noachian. In the much higher resolution (~0.2 - 20 m/pixel) MOC, HiRISE and HRSC images, the Arabian Level exhibits evidence of terracing (potentially indicative of wave-cut erosion); however, the topographically lower/younger 'shore-lines' do not. The interior plains encompassed by these lower levels include vast expanses of coldclimate landforms, such as polygonal ground and scalloped depressions [8], a relationship that is consistent with either an initially warm, but progresssively cooling, aqueous environment - or initial conditions that were cold from the outset. In either case, the flow-front-like morphologies associated with the lower levels may have resulted from ice-shoving due to shortlived transgresssive events caused by later episodes of outflow channel activity around the northern plains [6].
Apparent discrepancies between the absolute elevation of the Arabian Level with the perimeter of an equipotential surface have been cited as potential serious weaknesses of the paleoocean hypothesis [2]. However, improved shoreline maps, based on the recent influx of new, higher-resolution images, combined with recognition of the potential effect of true polar wander on the post-ocean/ice-sheet deformation of shorelines [9] have helped resolve much of this disagreement.- Publication:
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European Planetary Science Congress
- Pub Date:
- September 2013
- Bibcode:
- 2013EPSC....8..865C