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Space Topics: Saturn

Hyperion

Chaotic Moon

Click to enlarge > Color mosaic of Hyperion Color mosaic of Hyperion from Cassini's flyby on September 26, 2005 at about 00:40 UTC. Credit: © 2005 Mattias Malmer; raw data courtesy of NASA / JPL / SSI

Size: Irregular, 410 x 260 x 220 kilometers - 8th largest moon of Saturn
Orbital radius: 1,464,100 kilometers - 24.3 Saturn radii
Orbital period: 21.3 days - 4/3 of Titan’s
Discovery: 1848 by George Phillips Bond and William Lassell

Hyperion is the largest highly irregularly shaped body in the solar system. Hyperion's self-gravity is not enough to crush its materials together and eliminate gaps in its interior. Its strange, spongy texture, its dark-floored craters, and its landslide morphology are very difficult to explain.

The Voyager 2 flyby of Hyperion revealed that Hyperion has no fixed spin axis. It may spin around one axis for a while, but disturbances from Titan's gravity can shift that spin axis. Hyperion and Titan are in a 4:3 orbital resonance, which means that Titan orbits Saturn 3 times for every 4 times Hyperion orbits. As a result, Hyperion gets periodic "shoves" from Titan's gravity as their orbits match up.

Flybys of Hyperion

NASA / JPL

Voyager 2
Closest view was on August 25, 1980 at approximately 00:40 UTC

Click to enlarge > NASA / JPL / SSI

Cassini
September 26, 2005 at 02:25:51 UTC
“15HY” flyby
Closest approach altitude 505.0 kilometers (313.8 miles)