Degradation of Victoria crater, Mars

The similar to 750 m diameter and similar to 75 m deep Victoria crater in Meridiani Planum, Mars, is a degraded primary impact structure retaining a similar to 5 m raised rim consisting of 1-2 m of uplifted rocks overlain by similar to 3 m of ejecta at the rim crest. The rim is 120-220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine craters 500-750 m across indicates that the original, pristine crater was close to 600 m in diameter. Hence, the crater has been erosionally widened by similar to 150 m and infilled by similar to 50 m of sediments. Eolian processes are responsible for most crater modification, but lesser mass wasting or gully activity contributions cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for similar to 50 m widening across a WNW-ESE diameter. The volume of material eroded from the crater walls and rim is similar to 20% less than the volume of sediments partially filling the crater, indicating eolian infilling from sources outside the crater over time. The annulus formed when similar to 1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped < 10-20 cm of darker, regional basaltic sands. Greater relief along the rim enabled meters of erosion. Comparison between Victoria and regional craters leads to definition of a crater degradation sequence dominated by eolian erosion and infilling over time.