Cassini Images Density Waves in Saturn's Rings

Explanation: What causes the patterns in Saturn's rings? The Cassini spacecraft just entering orbit around Saturn has started sending back spectacular images of Saturn's immense ring system in unprecedented detail . The physical cause for many of newly resolved ring structures is not always understood. The cause for the beautifully geometric type of ring structure shown above in Saturn's A ring , however, is hypothesized to be a spiral density wave . A small moon systematically perturbing the orbits of ring particles orbiting at slightly different distances causes such a density wave bunching. Also visible on the image right is a bending wave , a vertical wave in ring particles also caused by the gravity of a nearby moon. This close-up spans about 220 kilometers. Cassini is scheduled to take and send back images of the distant ringed Saturn and its unusual moons for the next four years.