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Published July 10, 1973 | Published
Journal Article Open

Mars: South polar pits and etched terrain


Sharply delineated closed depressions, one-half to tens of kilometers across, with 400 meters estimated maximum depth, are locally abundant in the south polar region. They indent the surface of a massive homogeneous blanket that mantles the cratered bedrock surface. Some pits extend through the blanket exposing the underlying rock floor, and, where the blanket is thin (50–100 meters), its extensive removal exposes large ares of exhumed rock floor producing a terrain described as etched. The blanketing material is speculatively interpreted to be an eolian sedimentary deposit containing a mixture of fine particulate matter, possibly including volcanic ash, and particles of frozen volatiles, principally CO_2and H_2O. Fields of dunes, groups of linear grooves and flutes, and an unusual scoured topography on the surface of layered blanketing material suggest strong wind action. For this reason, deflation by wind, aided by ablation (evaporation) of included frozen volatiles, is regarded as the most likely mechanism for producing the south polar pits and etched terrain. Pitted and etched terrains and the deposits into which they are cut suggest that the south polar region, and presumably the north polar area as well, have experienced alternating episodes of eolian deposition and erosion.

Additional Information

Copyright 1973 by the American Geophysical Union. (Received January 24, 1973; revised March 14, 1973.) So many people have played a part in contributing to the success of the Mariner 9 photographic mission that to enumerate any by name does disservice to others unmentioned. Those people who have had a role in this great scientific adventure will know it and hopefully will take satisfaction from the publication of the results. Contribution 2266, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.

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