The rings are nothing more than a dense swarm of tiny, interacting moons. In principle, you could find an orbit for every ring particle around Saturn if the particles did not interact with one another and change orbits slightly. Different kinds of forces act on ring particles of all sizes and modify their orbits. If you cannot track an object and predict its orbital path, you might call it a ring particle rather than a moon. The orbits of the largest particles in the rings probably change the least. However, we do not have much data on this question since the largest “ring particle” Voyager imaged was Pan, and we don’t know how Pan’s orbit may be changing with time. Cassini will provide a wealth of new data on Pan and will probably discover new moons embedded in the rings. You might ask: At what size something is no longer a moon but is just a “ring particle”? There’s no clear distinction. Suppose the ring particles sometimes stick together in larger collections of many particles, and sometimes break apart via collisions. In this case, do some “moons” come and go? There really is no sharp cutoff between a moon and a ring particle (or “ringberg”). The smaller the moon, the harder it is for it to maintain an empty gap around Saturn. We think that smaller “moons” might clear small areas that are then filled in with ring particles after the “moon” has passed by. However, maintaining a gap depends in part on the density of ring particles in the region in which the moon orbits. Denser regions like the A or B rings would require a larger moon to maintain a gap than a much more diffuse region such as the C ring. Hence, defining a moon as an object that maintains a gap in the rings would produce differing cutoffs in moon sizes for each ring region. It will be interesting to see just what definitions evolve once Cassini begins making its closer examination of Saturn’s rings!