Mathematics – Logic
Scientific paper
Apr 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011p%26ss...59..412s&link_type=abstract
Planetary and Space Science, Volume 59, Issue 5-6, p. 412-422.
Mathematics
Logic
5
Scientific paper
Flat-floored depressions with scalloped-shapes and spatially associated small-sized polygons (diameter <˜100 m) dot the landscape of western Utopia Planitia (centered at 45°N-95°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°-110°E, 35°-50°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.
Costard Francois
Fedorov Arkady
Gargani Julien
Marmo Chiara
Séjourné Arnauld
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