A tiny moon, probably no more than six miles in diameter, has been found in the division between the two outermost main rings of Saturn.
It is the second Saturnian moonlet to be found in a gap in the ring system and supports the suspicion that the little moons created the spaces by sweeping up particles from a once-uninterrupted ring.
The discoveries were made when scientists analyzed data radioed to Earth in 1980 and 1981 by two Voyager spacecraft passing Saturn. The first moonlet, in what astronomers know as the Encke gap, was found several years ago by Jeff Cuzzy and Mike Showalter at NASA's Ames Research Center in Sunnyvale, Calif. The second, in the Cassini division, has just been discovered by Essam Marouf of Stanford University's Center for Radar Astronomy.
Neither moonlet was seen directly, probably because they are made of dark material, perhaps ice mixed with carbon. Instead, astronomers found their wakes in nearby regions of rings. The wakes, much like those of boats, consist of ripples or waves propagating through the bits of ice and stone that make up the rings.
Because the moonlets orbit Saturn more slowly than the ring particles, their wake is like that of a rock in a stream.