The Asteroid Vesta Is Rounded and Shows Signs of Differentiation

Multiple Choice

The asteroid Vesta is rounded and shows signs of differentiation, even though it is only 525 km in diameter. What is believed to be the reason for this?

A) Vesta is unusually dense, so that, despite its small size, it has pulled itself gravitationally into a sphere.
B) Vesta was heated by a massive collision.
C) Vesta was heated by radioactivity soon after its formation.
D) Vesta was initially formed hot in the solar nebula and has managed to avoid large collisions ever since.