The space probe Dawn has been launched on September 27, 2007 toward the main asteroids belt. In July 2011, the probe came in orbit around Vesta and went to Ceres, arriving in 2015. This space probe is using an ionic engine as Deep Space One, putting it on a spiral path and using the gravitational help of the planet Mars.
During orbiting Vesta, the probe sent us images showing a large impact crater. This asteroid is differentiated; it has a 530km-diameter and an iron-nickel 220km-core with a basaltic crust. However, Vesta is half made of water ice.