Topography of the polar layered deposits of Mars

Abstract

Synthesis of polar topographic data derived from the Mariner 9 radio occultation, ultraviolet spectrometer, and television imaging experiments provides new information on the behavior of polar volatiles and the topographic configuration of the martian polar layered deposits. Gentle slopes in the vicinity of the south pole may serve to shift the point of minimum annual solar insolation from the pole to a site within the perimeter of the offset residual frost cap. Localized defrosting which gives rise to the dark-banded appearance of both residual caps correlates with a series of outward-facing slopes descending from central topographic highs. Stability of the volatile involved apparently is largely insolation controlled. The south polar residual cap lies entirely higher (at lower pressure) than the northern cap, implying that the south residual cap is an unlikely site for any permanent surface deposit of solid carbon dioxide. Photogrammetric models of both residual caps reveal a series of regularly spaced topographic undulations descending from central topographic highs within the underlying layered deposits. Scarplike to troughlike in cross section, these features slope 1°–5° and are 100–1000 m in local relief. The south polar layered deposits lie almost entirely at higher elevations than those in the north. Total thickness of the deposits is inferred to be 1–2 km in the south and 4–6 km in the north.

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