Saturn’s G Ring: Made by a Moon


Saturn G Ring

The bright arc within Saturn's G ring taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 9, 2009.

Credit: NASA/JPL/Space Science Institute

In the early 17th century, Galileo Galilei peered through his telescope and reported the planet Saturn as having ears. He was the first to peer at the planet’s dazzling ring system, now known to be composed of tiny orbiting particles of ice and dust. Observations of the rings are still yielding surprises.

Recent images from NASA’s Cassini spacecraft show a luminous dot speeding within the G ring, one of the planet’s faintest, least-understood rings. The orbiting body is a moon about 0.5 kilometers (0.3 miles) wide. Particles shed by this moonlet—and perhaps others like it yet to be discovered—make up the G ring. Prior to this discovery, the G ring was the only one of Saturn’s dusty rings that was not known to host a moon.