Slurry extrusion on Ceres from a convective mud-bearing mantle

Abstract

Ceres is a 940-km-diameter dwarf planet that is predominantly composed of silicates and water ice. In Ceres’ partially differentiated interior, extrusive processes have led to the emplacement on its surface of domes with heights of kilometres. Here we report the analysis of a gravity anomaly detected by the Dawn spacecraft, which is associated with the geologically recent dome Ahuna Mons. By modelling the anomaly with a mass concentration method, we determine that the subsurface structure includes a regional mantle uplift, which we interpret as a plume. This structure is the probable source of fluids forming Ahuna Mons and, together with constraints from the dome’s morphology, indicates a rheological regime corresponding to a slurry of brine and solid particles. We propose that the properties of such a solid–liquid mixture can explain the viscous relaxation and the mineralogy of the dome. The presence of a plume and of slurry material indicate recent convection in a mud-bearing mantle. The inferred slurry extrusion on Ceres differs from the water-dominated cryovolcanism of icy satellites, and so reveals compositional and rheological diversity in extrusive phenomena on planetary surfaces.