Hydration Features on Vesta's Surface Seen by the Dawn Visible and Infrared Spectrometer (VIR) Data

Abstract Understanding the sources of hydration on Vesta's surface provides insights into water origins in the inner solar system. We estimated the hydration content across Vesta's surface using new calibrated Dawn VIR data. High content of hydration (up to 1,000 ppm) was observed in previously identified carbonaceous chondrite (CC)‐rich regions. CC‐poor areas consistently showed around 100 ppm of solar wind‐induced hydration with no latitudinal dependence, likely due to Vesta's low surface temperatures and high axial tilt. Despite receiving less solar wind flux, Vesta's low‐latitude surfaces exhibit higher hydration content than the Moon's, attributed to better hydration retention at lower temperatures (e.g., ∼80°) where the maximum daytime temperatures are less than ∼280 K, the Moon can effectively retain around four to five times hydration as that on Vesta, which is in great accordance with the greater solar wind fluence received by the Moon at its heliocentric distance. Our study suggested that the formation of water by solar wind implantation is ubiquitous on airless bodies in the solar system and that the retention of solar wind water is dominantly controlled by surface temperatures of these bodies.