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Possible occurrence and origin of massive ice in Utopia PlanitiaF. M. Costard recently discovered a large field of possible thermokarst depressions near latitude 45 deg N, longitude 270 deg, in western Utopia Planitia. Oval to circular pits are typically 300-1000 m across and approximately 25 m deep; larger depressions, 3-5 km across, are compound and seem to have formed by coalescence of smaller pits. Small domical hills occur on the floors of two pits. These depressions characteristically have steep, scalloped edges and one or more inner benches. Truncation relations of the benches suggest a discontinuous, lenslike stratification of the material in which the pits are developed. Based on a close analogy in form and scale with coalesced thawlake basins (alases) on Earth, the Martian pits may have formed by thermophysical interactions of pooled water with ice-rich permafrost. This interpretation is not unique; sublimation of ice-rich permafrost or possibly even eolian processes acting on ice-free material might have formed the pits. However, the regional setting contains many other indications of massive ice. Some of these features are examined.
Document ID
19940015917
Document Type
Conference Paper
Authors
Kargel, J. S. (Geological Survey Flagstaff, AZ, United States)
Costard, F. M. (Centre National de la Recherche Scientifique Caen, France)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Lunar and Planetary Inst., Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution
Subject Category
LUNAR AND PLANETARY EXPLORATION
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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