Meteorites from the asteroid Vesta contain a record of an intense bombardment of the inner Solar System by asteroids about 4 billion years ago, reports a study published online this week in Nature Geoscience. The research suggests that unusually energetic impacts on Vesta were caused by the same gravitational disturbance that put unusually numerous large asteroids on a collision course with the Earth and Moon at that time.
Simone Marchi and colleagues examined evidence of ancient impact-reset meteorites from Vesta, and used simulations to determine the properties of the impacts required to generate sufficient heat to reset the rocks. They found that the impacts must have occurred at much higher velocities than usually seen in collisions between objects in the asteroid belt. They suggest that although bombardment of inner Solar System bodies left fewer objects in the asteroid belt to strike Vesta, the asteroid experienced more high-velocity impacts.