Elevated Flat Floor Depressions in the Southern Highlands of Mars 500 views

Recent missions to Mars have produced a <18m/pixel image coverage over significant portions of the pla net's surface allowing systematic investigations of many meter - to - decimeter -scale features which were previously irresolvable. Utilizing images from MOC, HiR|SE, CTX, THEMIS VIS, and HRSC orbiting imaging systems I have identified a latitude - dependent type of depression found on the rims of many craters here in referred to as Elevated Flat Floor Depressions (EFFDs). A detailed survey of these features was conducted across the Southern Highlands of Mars. I have found that EFFDs are characterized by: 1) A distinctive morphology. EFFDs are approximately 1000m in diameter, orientated parallel to the crater rim, and have well defined steep bounding scarps with flat floors and lacking evidence of surfical fluvial or creep related inputs or outputs of sediment, resulting in conspicuous volume loss. 2) A restricted geographic range. EFFDs are located in a latitude band between 30° and 60° in both hemispheres and are situated near the apex of crater rims. EFFDs decrease in frequency and change their axial orientation relative to their distance from the crater rim. 3) EFFDs are recent formations, likely Amazonian in age (<l.8 Ga bp). EFFDs have a "fresh" appearance with steep scarps and evidence of recent backwasting. As these features are superimposed on highly eroded terrains they must be formed by relatively recent landform modification and post - date crater formation and the Noachian fluvial period. I conclude that EFFDs morphology, latitude dependence, and volume loss is most consistent with periglacial processes similar to terrestrial thermokarst depressions. I propose that crater rims, as high erosional environments with strong winds and steep slopes, create conditions in which a protective cover is removed preferentially and a subsurface layer composed ofan ice and dust mixture is exposed and sublimates into the atmosphere. Note: Abstract extracted from PDF file via OCR

MS (Master of Science)

English

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2009-12-01