Probing the history of Solar System through the cratering records on Vesta and Ceres

Abstract

Through its connection with HED meteorites, Vesta is known as one of the first bodies to have accreted and differentiated in the Solar Nebula, predating the formation of Jupiter and surviving the violent evolution of the early Solar System. The formation time of Ceres instead is unknown, but it should not postdate that of Jupiter by far. In this work we modelled the collisional histories of Vesta and Ceres at the time of the formation of Jupiter, assumed to be the first giant planet to form. In this first investigation of the evolution of the early Solar System, we did not include the presence of planetary embryos in the disk of planetesimals but we concentrated on the role of the forming Jupiter and the effects of its possible inward migration due to disk-planet interactions. Our results clearly indicate that the formation of the giant planet caused an intense early bombardment in the orbital region of the Main Asteroid Belt. According to our results, Vesta and Ceres would not have survived the Jovian early bombardment if the disk was populated mainly by large planetesimals like those predicted to form in turbulent circumstellar disks. Disks dominated by small bodies, like those predicted to form in quiescent circumstellar disks, or with a varying fraction of the mass in the form of larger (D \geq 100 km) planetesimals represent more favourable environments for the survival of the two asteroids. In those scenarios where they survive, both asteroids had their surfaces saturated by craters as big as 150 km and a few as big as 200 - 300 km. In the case of Vesta, the Jovian early bombardment would have significantly eroded (locally or globally) the crust and possibly caused effusive phenomena similar to the lunar maria, whose crystallisation time would then be directly linked to the time of the formation of Jupiter.