Question

Saturn's rings have what looks like extremely dark bands. What are they?

(a) Regions of dark (low reflectivity) material.
(b) Gaps between the rings caused by collisions with other moons in orbit around Saturn.
(c) Shadows cast by other moons in orbit around Saturn.
(d) Gaps between rings caused by the gravitational pull of other moons in orbit around Saturn.
(e) Slightly warmer regions of the ring, where the ices have evaporated to form gas.

Answer 1

The dark bands in Saturn's rings are gaps caused by gravitational resonances with moons, where the moons' gravity perturbs and shifts particles, creating clear spaces. The most pronounced gaps are maintained by shepherd moons.

Step-by-step explanation:

The dark bands that you observe in Saturn's rings are actually gaps in the rings. These gaps are the result of gravitational resonances with moons that orbit Saturn. The resonances occur when the orbital periods of ring particles and those of the moons have simple ratios, like 1:2 or 2:3.

For example, within the Cassini Division, particles that would orbit with a period one-half that of Saturn's moon Mimas get perturbed by Mimas's gravitational pull, leading them to be pushed into new orbits outside the gap. This constant gravitational tugging over time has cleared the Cassini Division of most of its ring material. The major gaps in the rings are caused by shepherd moons like Pandora and Prometheus for Saturn's F Ring, which help to maintain the shape and sharp edges of the rings.