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Summary
Vesta is the second most massive asteroid in our solar system and provides the opportunity to study the early Earth as a developing planet while it was still barely one-sixth the size of the Moon. Add to that what appear to be samples from this once molten protoplanet and you have the decades of case building and motivation for the spacecraft exploration of Vesta—the Dawn mission (1). Results of this mission, reported by Prettyman et al. (2) on page 242 and Denevi et al. (3) on page 246 in this issue, not only tell us about the birth and evolution of terrestrial planets, but also offer new insights into the distribution of water in our solar system.