The Real Shepherd Moons
The American space craft Voyager passed the gas planet Saturn in 1981. During the passage, Voyager discovered two small moons Prometheus [the Greek giant who gave the fire to the humans] and Pandora [the virgin who opened the secret box, which contained all the horrors of the world ]. The moons stabilise the so-called F-ring of Saturn. The moons circle around the ring in different locations. Pandora is 1,000 km farther away from the ring than Prometheus, attracting the dust particles of the F-ring. The dust particles are braked and draw closer to the surface of Saturn. If the particles were not braked they would be diffused and the F-ring would disappear. Prometheus, on the other side of the ring, prevents the F-ring falling down on the surface of Saturn.
Since a 1995 picture of the F-ring from the Hubble telescope, there have been speculations about the positions of the moons. A theory claims that the exact position of the moons is impossible to measure, as the moons are part of a chaotic system. Another interesting question is: Which other shepherd moons control the other rings?