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Saturn's Spongy Moon, Hyperion, Gets Final Close-Up from Cassini Probe

by Alan Boyle /  / Updated 

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The SpongeBob Roundpants of the solar system, Saturn's moon Hyperion, shows off its weirdly cratered surface in pictures from what's likely to be its final photo op for the foreseeable future.

The images were captured by NASA's Cassini orbiter during a May 31 flyby.

Cassini has been circling Saturn for almost 11 years, and Hyperion has gotten multiple close-ups over all that time. Last month's flyby, which came within 24,000 miles (38,000 kilometers) of the moon, was Cassini's last scheduled close encounter with Hyperion. The spacecraft is making its final rounds, leading up to the mission's end and a final, fatal plunge into Saturn's cloud layers.

Hyperion looks like a bath sponge in space, and Cassini's earlier observations helped scientists figure out why: The moon is composed mostly of water ice that's spongy and porous — so porous that 40 percent of Hyperion's volume consists of empty space. As a result, any object that hits the surface sinks right in — and the crater that's created becomes just another hole in the sponge.

It could be a long time before another probe comes as close to the 225-mile-long moon: NASA and the European Space Agency have been talking about a follow-up mission to the Saturn system, but nothing concrete is in the works yet. Any such mission wouldn't focus on Hyperion, but instead on a couple of other Saturnian moons, Titan and Enceladus.

For more views of Cassini's last hurrah at Hyperion, check out NASA's Cassini mission Web portal and the Cassini imaging team's CICLOPS website.

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