NASA ready to launch Dawn probe to asteroid belt

"From that we try to work back to how the whole thing was put together and what happened to it," said lead scientist Chris Russell, with the University of California at Los Angeles.

After six months of observations, Dawn will leave orbit and begin a three-year trek to the dwarf planet Ceres, the king of the asteroid belt. Though relatively close to Vesta, icy Ceres formed under vastly different circumstances. It contains water-bearing minerals and possibly a weak atmosphere.

By comparing the two worlds, scientists hope to learn more about how the solar system formed.