Erosion of Volatiles by Micrometeoroid Bombardment on Ceres and Comparison to the Moon and Mercury

Abstract

Abstract Ceres, the largest reservoir of water in the main belt, was recently visited by the Dawn spacecraft, which revealed several areas bearing H2O-ice features. Independent telescopic observations showed a water exosphere of currently unknown origin. We explore the effects of meteoroid impacts on Ceres by considering the topography obtained from the Dawn mission using a widely used micrometeoroid model and ray-tracing techniques. Meteoroid populations with 0.01–2 mm diameters are considered. We analyze the short-term effects Ceres experiences during its current orbit, as well as long-term effects over the entire precession cycle. We find that the entire surface is subject to meteoroid bombardment, leaving no areas in permanent shadow with respect to meteoroid influx. The equatorial parts of Ceres produce 80% more ejecta than the polar regions due to the large impact velocity of long-period comets. Mass flux, energy flux, and ejecta production vary seasonally by a factor of 3–7 due to the inclined eccentric orbit. Compared to Mercury and the Moon, Ceres experiences significantly smaller effects of micrometeoroid bombardment, with a total mass flux of 4.5 ± 1.2 × 10−17 kg m−2 s−1. On average, Mercury is subjected to a 50× larger mass flux and generates 700× more ejecta than Ceres, while the lunar mass flux is 10× larger and the ejecta generation is 30× larger than on Ceres. For these reasons, we find that meteoroid impacts are an unlikely candidate for the production of a water exosphere or significant excavation of surface features. The surface turnover rate from the micrometeoroid populations considered is estimated to be 1.25 Myr on Ceres.