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Article Dans Une Revue Planetary and Space Science Année : 2011

Scalloped depressions and small-sized polygons in western Utopia Planitia, Mars : a new formation hypothesis

Résumé

Flat-floored depressions with scalloped-shapes and spatially associated small-sized polygons (diameter < similar to 100 m) dot the landscape of western Utopia Planitia (centered at 45 degrees N-95 degrees E). The scalloped depressions are thought to be the result of ice-rich regolith undergoing degradation by sublimation or thaw. Current models suggest that the formation and development of the depressions occur in a poleward direction due to the enhanced sublimation of their equator-facing slopes. By contrast, we propose a conceptual model that shows the equatorward growth of depressions due to preferential degradation by sublimation of their pole-facing slopes. Our model is based on a geomorphological study of the depressions and small-sized polygons in western Utopia Planitia (80 degrees-110 degrees E, 35 degrees-50 degrees N), using images from the High Resolution Imaging Science Experiment (HiRISE) and topographical data from the Mars Orbiter Laser Altimeter (MOLA) and a HiRISE stereo Digital Elevation Model (DEM). Here we describe (i) a morphological evolution of small-sized polygons within the depressions, from low-centered to high-centered, that facilitates one's understanding of depression growth and development: and (ii) occurrence of v-shaped alcoves, failure cracks and semicircular hollows that point to a retrogressive degradation of the pole-facing slopes of depressions. We propose that the development of the depressions is due to heightened insolation of their pole-facing slopes, leading to enhanced sublimation of ground-ice. Based upon the inferred asymmetric insolation, we suggest that the equatorward expansion of depressions occurred during recent high-obliquity periods of Mars. (C) 2011 Elsevier Ltd. All rights reserved.

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Planétologie
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Dates et versions

hal-00572378 , version 1 (01-03-2011)

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  • HAL Id : hal-00572378 , version 1

Citer

A. Séjourné, F. Costard, J. Gargani, R.J. Soare, A. Fedorov, et al.. Scalloped depressions and small-sized polygons in western Utopia Planitia, Mars : a new formation hypothesis. Planetary and Space Science, 2011, 59 ((5-6):), pp.412-422 (IF 2,067). ⟨hal-00572378⟩
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