The morphologic and morphometric characteristics of craters on Ceres and implications for the crust

Abstract

The Dawn spacecraft revealed a heavily cratered surface of the dwarf planet Ceres. These impact craters can be used to uncover the target properties of Ceres by analyzing the morphologic and morphometric characteristics. A near-global crater database containing 44,594 craters with diameters (D) ≥ 1.0 km in the latitude range 84.66°S–89.62°N over all longitudes has been developed to further understand the target properties of Ceres. For this purpose, various interior morphologies were classified such as central peaks, central pits, and lobate flows. Central floor pit craters were only observed in the northern hemisphere on Ceres indicating a weaker crustal strength. Investigations into the peak-to-crater diameter ratio (Dpk/Dc) implies the crust of Ceres has strength more similar to rocky Mercury than to Mars which exhibits localized areas of the crust containing large amounts of ice, or the volatile-rich crust of Ganymede. The Dpk/Dc, however, does display regional variations, with the northern hemisphere having a larger Dpk/Dc consistent with a more volatile-rich crust. Analysis of the depth-diameter ratio for fresh impact craters suggesting the simple-to-complex transition diameter (Dsc) of ~10.0 km and the onset diameters for central peaks indicate a Dsc of ~17.0 km. This is higher than expected if Ceres is a purely icy body and lower than expected if Ceres is a completely rocky body. These results indicate that Ceres has a mixed rock/ice composition, as proposed by other studies.