Saturn’s rings have circular orbits, but they revolve at various speeds.
Parts of a single ring even orbit Saturn at different rates.
For instance, the outer edge of ring E, furthest from the planet, has an orbital period of 4 hours, but the inner edge, some 180,000 miles (288,000 km closer) takes 22 hours to orbit.
The E ring has both the slowest and fastest orbits of all the rings around Saturn.
The E ring is a diffuse disk consisting mostly of ice, with silicates, carbon dioxide and ammonia, and unlike the other rings, it is composed of microscopic rather than macroscopic particles.