Icy Enigma Between Mars and Jupiter | Protoplanet Ceres | Ceres, 590 miles (950 kilometers) in diameter, is thought to be a surviving protoplanet, or planetary embryo, formed 4.57 billion years ago in the earliest days of our solar system. A year on Ceres is 4.6 Earth years long. Ceres rotates every 9 hours and 4 minutes. At the start of its encounter in early 2015, the Dawn spacecraft took photos of Ceres with greater clarity than any before...
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