The Mystery of Ceres' Activity

In recent years, the dwarf planet Ceres has been found to release water vapor. Detailed investigation of the surface and subsurface by NASA's Dawn mission reveal localized patches of surface ice and an ice abundance of around 10% in the shallow subsurface, within a meter below the surface. Landis et al. (2019, https://doi.org/10.1029/2018JE005780) quantify the expected sublimation from the surface and subsurface ice reservoirs at Ceres, and the expected evaporation rates are factors of several lower than the observed ones. Although consideration of additional processes may possibly reduce the discrepancy, the origin of Ceres' exosphere is not yet clear.