Martian fluidized crater morphology: Variations with crater size, latitude, altitude, and target material

On the basis of morphology of the exterior deposits of 1558 fresh Martian impact craters, 6 crater types are defined, and the incidence of each crater type on 10 different geological units is documented. It is shown that several crater types are preferentially associated with specific target materials: radial textured craters are found primarily on Tharsis and Elysium lavas, a type of crater here called ‘pancake craters’ on fractured terrain, old lavas, and channel materials. The occurrence of secondary craters is also strongly terrain dependent. Three times as many craters on young lavas have secondary craters as compared to those craters on ridged and cratered plains materials, and 10 times as many have secondary craters when compared to primary craters on ancient terrain materials. The maximum radial extent of fluidized ejecta blankets is demonstrated to be a function of both crater altitude and latitude. The most extensive ejecta units are found at low altitudes and high latitudes, while the least mobile ejecta is located at high elevations and close to the equator. Only pancake craters exhibit any pronounced latitudinal variation in their distribution. These craters are almost exclusively located poleward of latitudes 40°N and 40°S. For the majority of the sample craters (N = 1333), there is no such systematic latitudinal variation in crater occurrence.