The cratering record, chronology and surface ages of (4) Vesta in comparison to smaller asteroids and the ages of HED meteorites

Abstract

We derived model functions for the crater production size-frequency distribution and chronology of the asteroids 951 Gaspra, 243 Ida, 21 Lutetia and 4 Vesta, based on a lunar-like crater production function and a lunar-like chronology with a smooth exponential decay in impact rate for the first ~1Ga of Solar System history. For Gaspra, Ida and Lutetia we find surface ages roughly in agreement with published data. Using the same approach for Vesta leads to results with high correlation to Ar–Ar reset ages of HED meteorites, for which a strong dynamical and spectroscopic connection to Vesta has been found. In contrast to recently published young formation ages of the Rheasilvia and Veneneia basins of about 1 and 2Ga, respectively, we find for Rheasilvia a formation age of 3.5±0.1Ga and for the Veneneia formation a lower limit of 3.7±0.1Ga. For comparison we also give surface model ages for a preliminary version of a chronology (pers. comm. D.P. O׳Brien) based on the Late Heavy Bombardment theory. Error bars presented in our work stem only from statistical analysis of measured crater distributions and do not include the uncertainty of the used chronology model.