July 20, 2007 — Saturn's brood just keeps on growing, with moon No. 60 officially joining the eclectic collection.
Scientists using the Cassini spacecraft first spotted the new moon in pictures taken May 30. They then backtracked and looked at archived images for more clues. It turns out the moon had been photographed several times between June 2004, when Cassini first arrived at Saturn, and last month, when the probe marked its third year as the planet's first and so far only artificial satellite.
The new moon, officially designated as S/2007 S 4, but which has been unofficially nicknamed "Frank," orbits Saturn between the paths of Methone and Pallene, two small sister moons also discovered in Cassini images in 2004. All three moons orbit between the larger satellites Mimas and Enceladus.
Like so many of Saturn's moons, Frank, which is about one mile wide, is believed to be mostly ice and rock. It circles its mother world at a distance of about 122,800 miles.
Scientists think Frank and its small sister moons may be the remains of a larger body or a collection of bodies.
"This trio of objects could be remnants of a collision or perhaps they are the lucky survivors of a larger population of material that failed to form a moon," said Cassini imaging team scientist Carl Murray, a professor at Queen Mary, University of London.
"Either way there does seem to be a family connection," he said.
Cassini, which is now credited with discovering five new Saturn moons, may have more answers in a few years. The probe is scheduled to fly relatively close to Frank in December 2009.
Since Cassini's launch in 1997, the number of known moons orbiting Saturn has more than tripled. In addition to Cassini images, ground-based telescopes have booted the number of Saturn satellites from 18 to 60.
"Every discovery every adds another piece to the puzzle and becomes another new world to explore," Murray said.
