New data that’s just been released from NASA’s Mercury Messenger spacecraft could reveal how Mercury formed and changed over the 4.5-billion-year history of the Solar System. The planet appears to have shrunk as it has aged. Denton Ebel is the curator of Meteorites at the American Museum of Natural History and is involved in educational outreach programs for the Mercury Messenger mission at the museum. He explains why scientists are finding new reasons to study the planet.