Ceres Crater Degradation Inferred From Concentric Fracturing

Abstract

AbstractThe dwarf planet Ceres exhibits a collection of craters that possess concentric fractures beyond the crater rim. These fractures typically range from a few hundred meters to a few kilometers in length and are less than 300 m wide. They occur preferentially on elevated regions around the crater and are located less than a crater radius beyond the rim. In total there are 17 craters exhibiting concentric fracturing beyond the rim. They are located in the midlatitudes. The craters' diameters range between 20 and 270 km. We investigate the concentric fractures of three craters (Azacca, Ikapati, and Occator) in detail and suggest that the formation of such concentric fractures can be explained by a shallow (<10‐km) low‐viscosity (~1020‐Pa·s) subsurface layer extending underneath the crater and its surroundings. Finite element modeling of such a scenario applied to a typical concentrically fractured crater of 50‐km diameter implies that the depth of the low‐viscosity layer is comparable to the crater depth and the layer does not extend to the surface. Given that not every crater of comparable size on Ceres exhibits concentric fractures, it is also suggested that these conditions are only met locally and may be related to the surface temperature. Correlations of concentrically fractured craters with other volatile related features, such as pitted terrains and floor fracturing, suggest that the low‐viscosity subsurface layer may be enriched in ice.