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Ice filled craters in Mars' north polar region — implications for sub-surface volatiles

There is much evidence to support the presence of surface water-ice in the North Polar Region, but the subsurface distribution is still unknown. To confirm or reject the past northern basin ocean hypothesis support is needed from the properties of the underlying sediments. As impact craters are a natural probe of the subsurface, we present a systematic study of impact craters above 65°N, to investigate the substrate in this region. We place particular emphasis on 17 craters that show convex-up positive relief in their centres distinct from a central peak, hereafter termed “lumps”.