Pedestal crater heights on Mars: A proxy for the thicknesses of past, ice-rich, Amazonian deposits

Mid-latitude pedestal craters on Mars offer crucial insights into the timing and extent of widespread icerich deposits during the Amazonian period. Our previous comprehensive analysis of pedestal craters strongly supports a climate-related formation mechanism, whereby pedestals result from impacts into ice-rich material at mid latitudes during periods of higher obliquity. The ice from this target deposit later sublimates due to obliquity changes, but is preserved beneath the protective cover of the armored pedestal. As such, the heights of pedestals act as a proxy for the thicknesses of the paleodeposits. In this analysis, our measurement of 2300 pedestal heights shows that although pedestals can reach up to 260 m in height, 82% are shorter than 60 m and only 2% are taller than 100 m. Mean pedestal heights are 48.0 m in the northern mid latitudes and 40.4 m in the southern mid latitudes, with the tallest pedestals located in Utopia Planitia, Acidalia Planitia and Malea Planum. We use these data in conjunction with prior climate model results to identify both regional and global trends regarding ice accumulation during obliquity excursions. Our data provide evidence for multiple episodes of emplacement and removal of the mid-latitude ice-rich deposit based on stratigraphic relationships between pedestal craters and the close proximity of pedestals with significantly different heights. 2010 Elsevier Inc. All rights reserved.