Io transit of Jupiter
Io transit of Jupiter The conspicuous black spot on Jupiter is Io's shadow and is about the size of the moon itself (3,640 kilometers or 2,262 miles across). This shadow sails across the face of Jupiter at 17 kilometers per second (38,000 mph). The smallest details visible on Io and Jupiter measure 150 kilometers (93 miles) across. J. Spencer/Lowell Observatory/NASA/ESA

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