Abstract

The orbital architecture of planets in the Solar System is thought to have been set shortly after its birth. However, ancient asteroid families are highly dispersed, suggesting that perhaps the Solar System remained chaotic until later in its history. Testing this possibility requires precise dating of the collisions that should have generated such families, but planetary surfaces record little to no information from this time. The meteorite record of asteroid collisions represents a separate and more complete archive of Solar System evolution. In this project, we leveraged recent methodological advances to build an extensive record of in-situ meteorite apatite U-Pb ages, sensitive to collisions that induce parent body break-up events. Most asteroid collisions in our record occurred 4480 +/- 20 million years ago. Only highly dispersed asteroid families are potentially co-eval with our U-Pb ages, demonstrating that strong perturbations modifying the orbital eccentricities and inclinations of asteroids were still operating at 4480 Ma. This is unexpected in scenarios where the planets completed their growth and acquired their current orbits in a few Myr within the dispersal of the protoplanetary disk. Our work provides unique evidence that the asteroid belt was still in a state of dynamical chaos 80 Myr after its formation.