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ScienceShot: Pac-Man Gobbles the Death Star

The Cassini spacecraft must have known April Fool's Day was coming up. It returned this temperature map—released yesterday—after its closest flyby ever of Saturn's icy moon Mimas last month. Shaped into the likes of the Death Star of Star Wars fame by the giant crater Herschel, 396-kilometer-diameter Mimas was expected to have its warmest surface temperatures on the equator, where it was early afternoon. Instead, it was warmest in the morning (all of 92 K), giving rise in the science team's temperature-calibrated color scheme to a very large Pac-Man. The warmer Herschel in Pac-Man's mouth makes sense, Cassini scientists say, because the crater could retain heat longer, but the gaping Pac-Man is a mystery. Perhaps it arises from a variation in the heat retention properties of surface ice. Now, on to Cassini's 67th flyby of Saturn's big haze-shrouded moon Titan on 5 April.