Closing in on HED meteorite sources

Abstract

Members of the Vesta dynamical family have orbital elements consistent with ejecta from a single large excavating collision from a single hemisphere of Vesta. The portion of Vesta’s orbit at which such an event must have occurred is slightly constrained and depends on the hemisphere impacted. There is some evidence for subsequent disruptions of these ejected objects. Spectroscopy suggests that the dynamical family members are associated with material from Vesta’s interior that was excavated by the event giving rise to the crater covering much of Vesta’s southern hemisphere. The 505-nm pyroxene feature seen in HED meteorites is relatively absent in a sample of Vesta dynamical family members raising the question of whether this collisional event was the source of the HED meteorites. Asteroids spectroscopically associated with Vesta that possess this feature are dynamically distinct and could have arisen from a different collisional event on Vesta or originated from a body geochemically similar to Vesta that was disrupted early in the history of the solar system.