NASA's Dawn mission to study two of the largest objects in the asteroid belt, Vesta and Ceres, has begun. Lying between Mars and Jupiter, the two very different bodies offer clues to planetary formation.
The craft will arrive at Vesta in 2011 and the dwarf planet Ceres in 2015.
In addition to being the first to orbit two solar bodies, Dawn is also powered by unique ion propulsion system briefly described by Scientific American in its story on the mission.
Top artist's rendering: William K. Hartmann Courtesy of UCLA. Side image: NASA/ Kim Shiflett