Care must be taken, though. Some very large asteroids are differentiated, which means that when they formed and were still molten, heavy metals and other dense materials sank toward the center, while lighter, rocky material floated nearer to the surface. A large enough impact could excavate an asteroid’s depths and shallows alike, creating a family with a mix of compositions. The Vesta family is an example of this. (Vesta is the second-largest object in the main asteroid belt after Ceres, and both Vesta and Ceres are actually considered to be protoplanets by planetary astronomers.)