| Risultati della ricerca nelle immagini - "Amphitrites" |
PSP_004867_1220_RED_abrowse-00.jpgIce Processes in Amphitrites Patera (CTX Frame - Natural Colors; elab. Lunexit)84 visiteThis image captures an impact crater on the surface of Amphitrites Patera, an ancient volcano on the southern margin of the giant Hellas Basin. The Hellas Basin was formed by a very large impact into the Southern Highlands early in the geologic history of Mars. The basin has a number of volcanoes along its margin, perhaps because magma could take advantage of the deep cracks in the crust that resulted from the impact.
Amphitrites Patera is far enough South to approach the Martian Antarctic and there is evidence for large amounts of ice in the ground. As in the Polar Regions of Earth, the icy ground (permafrost) is able to move and be modified by a variety of processes. In this case, the rim of the small impact crater is filled with a honeycomb of cracks. These are likely to have formed where dust- and soil-covered ice or ice cemented soil was cracked by thermal contraction in the winter. Subsequently, the underlying ice was able to escape into the atmosphere (sublimate) allowing the ground along the cracks to collapse. The only place where large boulders are visible is along the rim of the crater; this is probably where the boulders were not so deeply buried by the icy layer. MareKromium
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PSP_004867_1220_RED_abrowse-01.jpgIce Processes in Amphitrites Patera (EDM - Natural Colors; elab. Lunexit)55 visiteThe Martian Atmosphere was dusty at the time this image was acquired, so small imperfections in the processing are very visible in the standard image products.
MareKromium
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PSP_005632_1225_RED_abrowse~0.jpgPartially Exhumed Crater in Amphitrites Patera (MULTISPECTRUM; elab. Lunexit)54 visiteThe terrain in this image is located in Amphitrites Patera, South-West of Hellas Basin. This area constitutes the interior of an ancient impact crater that was filled by a layer of smooth material, possibly composed of ash and dust, mixed with interstitial ice (ice filling spaces between dust and ash grains).
The curved ridge toward the lower left of the image is a remnant of the crater rim that was exhumed by erosion of the filling material. The morphology (appearance and shape) of the small, scalloped depressions, which we observe within the smooth material, suggests that the erosion process was sublimation (the process of a material going directly from a solid state to a gaseous state).
Scalloped depressions are a typical feature of the Mid-Latitudes of Mars between 40 and 60°. They usually have a steep pole-facing scarp (cliff), displaying series of small pits and fractures and a gentler, smoother, equator-facing slope. This asymmetry is most likely due to differences in solar heating.
The large scalloped depressions appear to have formed from the coalescing of multiple, smaller scalloped depressions. Their formation may be an ongoing process, although no definitive evidence has been uncovered so far.MareKromium
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