Swiss-Cheese Saturn Moon

Cassini image of Saturn’s small moon, Epimetheus. Click image for large view.
Image Credit: Cassini Imaging Team/Boulder/

An image of Saturn’s small moon, Epimetheus (epp-ee-MEE-thee-uss), was captured by the Cassini spacecraft in the closest view ever taken of the pockmarked body.

Epimetheus is irregularly shaped and dotted with soft-edged craters. The many large, softened craters on Epimetheus indicate a surface that is several billion years old.

The moon shares an orbit with another of Saturn’s small moons, Janus. The two dance in a planetary tango as they move in almost identical orbits, exchanging orbits every four years, instead of colliding.

Both play a role in creating intricate waves in Saturn’s rings; both have densities significantly lower than that of solid ice, suggesting they may be "rubble piles" held together by gravity.

At 116 kilometers (72 miles) across, Epimetheus is slightly smaller than Janus at 181 kilometers (113 miles) across.

Spectra of Epimetheus from the Cassini visual infrared mapping spectrometer indicate that the moon is mostly water ice.

The seven year voyage will end when Cassini’s main engine is fired, the spacecraft is slowed, and the probe enters Saturn orbit on July 1, 2004.

The Cassini-Huygens mission is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington, D.C.

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