Simulation of a one-two punch that nearly destroyed the asteroid Vesta

Artist's impression of the huge impact that deformed the protoplanetary asteroid Vesta, leaving the large impact basin we see today.

Martin Jutzi

The large asteroid Vesta is a true relic of our Solar System's early history. Thanks to the recent detailed study by the Dawn spacecraft, we know it's an intact protoplanet, the type of object that collided and aggregated into the planets early in our Solar System's history. Vesta's southern regions are scarred by a huge impact basin consisting of overlapping craters that cover a significant fraction of the asteroid's surface. Now, a new simulation may show how Vesta survived its violent past, and how the giant impact scar and some other significant surface features came to be.

The simulation—created by M. Jutzi, E. Asphaug, P. Gillet, J.-A. Barrat, and W. Benz—began with a fully three-dimensional model of Vesta's interior and surface. The researchers then modeled two successive impacts at nearly the same location. The impacts in this model reworked the entire asteroid, and accurately reproduce many of its existing features. Differences in the geological content of the surface didn't match observations, however, so some of the initial assumptions of the model may need modification.

Many asteroids are rubble, debris held together by mutual gravitation. Vesta, on the other hand, has a differentiated interior, much like Earth: it has a solid core surrounded by some sort of mantle. That means Vesta is a protoplanet, one of many small objects that populated the early Solar System. According to the widely accepted models of planet formation, most of the protoplanets either shattered during collisions or merged to make planets.