Pioneering spacecraft Dawn blasts off on a mission to explore two giant asteroids between Mars and Jupiter. Dawn's targets are two of the largest objects in the asteroid belt, the rocky body Vesta, which is similar to Earth's moon, and the icy dwarf planet Ceres. Although the objects are relatively close to each other, they formed under vastly different conditions. Scientists are eager to compare the two worlds to learn more about the original materials and processes of the solar system's creation. Dawn is expected to reach Vesta in four years and spend about six months in orbit before continuing on to Ceres.