Cold and dry processes in the Martian Arctic: Geomorphic observations at the Phoenix landing site and comparisons withterrestrial cold desert landforms

摘要

We analyze Surface Stereo Imager observations of rocks, sediments, and permafrost-related landforms in the vicinity of the Phoenix lander, comparing the imaged features to analogous examples of physical weathering and periglacial processes observed in the Antarctic Dry Valleys. Observations at the Phoenix landing site of pitted rocks, "puzzle rocks" undergoing in-situ breakdown, perched clasts, and thermal contraction crack polygon morphologies strikingly similar to terrestrial sublimation polygons, all strongly suggest that stable (non-churning) permafrost processes dominate the Phoenix landing-site. Morphological evidence suggests that cold-desertt processes, in the absence of wet active-layer cryoturbation, and largely driven by sublimation of buried ice (either pore ice, excess ice, or both) are shaping the landscape.