This sequence of three images, obtained by NASA's Cassini spacecraft over the course of about 10 minutes, shows the path of a newly found moonlet in a bright arc of Saturn's faint G ring, announced ny NASA on March 3, 2009. In each image, a small streak of light within the ring is visible. Unlike the streaks in the background, which are distant stars smeared by the camera's long exposure time of 46 seconds, this streak is aligned with the G ring and moves along the ring as expected for an object embedded in the ring. Cassini scientists interpret the moving streak to be reflected light from a tiny moon half a kilometer (a third of mile) wide that is likely a major source of material in the arc and the rest of the G ring. (UPI Photo/NASA) | License Photo

The Cassini spacecraft wide-angle camera captured this view of Saturn at a distance of approximately 1.23 million kilometers (764,000 miles) on January 19, 2007. Taking in the rings in their entirety was the focus of this particular imaging sequence. Therefore, the camera exposure times were just right to capture the dark-side of its rings, but longer than that required to properly expose the globe of sunlit Saturn. Consequently, the sunlit half of the planet is overexposed. This view is a mosaic of 36 images, 12 separate sets of red, green and blue images taken over the course of about 2.5 hours, as Cassini scanned across the entire main ring system. (UPI Photo/NASA/JPL/Space Science Institute) | License Photo

PASADENA, Calif., March 3 (UPI) -- The U.S. space agency says its Cassini spacecraft has found a moonlet within Saturn's G ring that may be a main source of the G-ring and its single ring arc.

National Aeronautics and Space Administration scientists analyzed images acquired by Cassini during the course of about 600 days and found the tiny moonlet, about one-third of a mile in diameter, embedded within a partial ring, or ring arc, previously found by Cassini in Saturn's G ring.


"Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd," said Matthew Hedman, a Cassini associate at Cornell University. "The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring."

Saturn's rings were named in the order they were discovered, scientists said. The G ring is one of the outer rings and within it there is a relatively bright 150-mile-wide arc of ring material that extends 90,000 miles, or one-sixth of the way around the ring's circumference.

The discovery brings the number of Saturnian ring arcs with embedded moonlets found by Cassini to three.

The finding was announced Tuesday in an International Astronomical Union circular.