I tried simulating a massless satellite in a roughtly 5::3 resonance
with a moon orbiting a large planet
(http://burtleburtle.net/bob/physics/rings.html). It's strobe,
showing the planet and moon exactly once per orbit, so the moon
appears to stay still. Since the satellite moves around, you get the
same pattern you'd get if you filled the whole of the satellite's
orbit with tiny particles. If you watch it for awhile, you'll see it
forms braided waves. However, these waves go out to the edge and in
again. It's symmetric if you flip the image along the line connecting
the planet to the moon. The images we're getting back from Saturn
don't show that symmetry. That lack of symmetry rules out all the
purely gravitational things I can think of.