Degradational Morphologies of Mid-latitude Martian Craters

Details Degradational Morphologies of Mid-latitude Martian Craters Degradational Morphologies of Mid-latitude Martian Craters

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p31b0145b&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #P31B-0145

Mathematics

Logic

5419 Hydrology And Fluvial Processes, 5420 Impact Phenomena, Cratering (6022, 8136), 5422 Ices, 6225 Mars

Scientific paper

The degradation of Martian craters in ice-rich environments provides clues to regional geologic history, as well as to the source of the ice (i.e., whether it was present as ground ice at the time of impact or if it has since been emplaced from the atmosphere). Features such as arcuate ridges, gullies, and flow lobes can be used to understand degradational history and constrain the distribution and abundance of ground ice. Two study areas have been selected to identify and examine these features; one in the northern mid-latitudes in Arabia Terra along the dichotomy boundary (30-50 deg. N, 0-40 deg. E) and one in the southern mid-latitudes in the highlands east of Hellas basin (30-60 deg. S, 110-150 deg. E). Previous studies in the Newton Basin region have shown that arcuate ridges and gullies are mainly found in craters 2-30 km in diameter; the orientation of these features on crater walls has also been found to be dependent on latitude, with a shift from pole-facing to equator-facing walls at about 45 deg. S, suggesting that their formation is related to climatic changes driven by obliquity cycles and deposition of ice-rich mantles. Potential ice-rich flow lobes are typically found in larger craters, which also commonly contain other features consistent with the flow of water or ice, including trough- like valley networks (sometimes filled with potentially ice-rich material), gullies, narrow runoff channels in and around the crater, mantled floor deposits, and lobate ejecta. Crater diameter, latitude, and crater wall orientation seem to control these features and their interrelationships. A thorough survey of THEMIS VIS images of the southern region has revealed the presence of a multitude of lobate flow features on the walls of craters throughout the region, typically on the pole-facing side, with a dependence on latitude and crater diameter. We have identified 24 craters with lobate flows on their walls, primarily between 35 and 50 deg. S, and distributed throughout the region longitudinally. Nearly all of the lobes are on pole-facing walls; however, these are found only as far south as -45 deg. South of -50 deg. two craters are observed with lobes on equator-facing walls. This orientation dependence on latitude is consistent with previously determined orientation results for gullies and arcuate ridges.

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