Saturn's mysterious black-and-white moon

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Carolyn Porco‘s Saturn imaging team has found “tell-tale clues” to a centuries-old mystery surrounding Saturn’s moon Iapetus — why is it stark white on one side, coal black on the other? It’s a striking oddity in a sky full of gray rocks. As the CICLOPS site reports, the white side of this moon is covered with brightly reflective ice, while sunlight has melted the ice on the dark-colored side, revealing the moon’s surface. Watch Carolyn Porco’s 2007 TEDTalk to learn more about this intriguing planet and its moons.