The Dawn spacecraft, after a voyage of nearly four years driven by ion engines, has finally entered into orbit around the asteroid Vesta. The second-largest body in the main asteroid belt, Vesta is believed to be the source of many of the meteors that impact Earth in geologically recent times (i.e. post-dinosaurs).
http://dawn.jpl.nasa.gov/feature_stories/close-up_asteroid_vesta.asp
