Pedestal craters on Ganymede

The high-resolution Voyager images of Ganymede show a class of fresh craters 6-89 km in diameter which is distinguished by an ejecta blanket similar to those seen for some types of Martian craters. One hundred and eighty-five were identified and studied for trends with respect to latitude, longitude, and terrain type. No correlation of the ratio of ejecta diameter to crater diameter was found as a function of latitude or longitude, and there is only a suggestion of a trend in this ratio with respect to major terrain types. Central peak frequency is greatest for the smaller crater diameters. Central pit occurrence dominates central peak occurrence at crater diameters of about 35 km. It is concluded that the ejecta morphology probably results from impact into an icy target. The question of whether atmospheric ejecta-particle drag contributes to ejecta blanket morphologies on planets with an atmosphere cannot be resolved entirely from the Voyager images.