Spectral Evidence for Irradiated Sodium Chloride on the Surface of 1 Ceres

Bright spots on the surface of Ceres exhibit a mineralogy resulting from aqueous processes that hint at past elements of an aqueous world. Reports of hydrated sodium chloride (hydrohalite) at Occator crater suggested that the salts may result from deep brines that reached the surface recently or currently, but the spectral characteristics of alkali halides make their identification difficult. However, anhydrous sodium chloride (halite) develops readily identifiable absorption features when exposed to a radiation environment of high energy particles. We report on spectroscopic evidence, in the form of irradiation-formed color centers, that suggests halite is a component of the bright surface features at Ceres. The spatial extent and inferred abundance are found to be greater than previously reported for hydrohalite. These findings imply that the emplacement of endogenic sodium chloride on the surface occurred via a suite of processes and that subsurface liquid water environments may have persisted through time.