Message #234912

[Erika Zimney]

Spongy Tumbler

Image courtesy Caltech/SSI/NASA

Cassini snapped this close-up of Hyperion's limb during the spacecraft's August 25 flyby. The sponge-like moon has been known to scientists since 1848 and was named after one of the Titans of Greek mythology.

However, Hyperion is one of Saturn's most distant moons and is relatively small, at about 168 miles (270 kilometers) wide. What's more, the moon's potatolike shape causes Hyperion to "tumble" along on its irregular orbit-the only known moon to have such a chaotic rotation.

The moon's wild movements make it nearly impossible for scientists to predict which areas will be visible at any given time, making it hard to target specific areas for imaging. The newly released pictures from Cassini's flyby therefore revealed some regions of Hyperion for the first time.

(Related: "Saturn's 'Walnut' Moon Mystery Cracked?")

Published August 31, 2011