Question

28) What process(es) cause the gaps in the rings of Saturn?

Answer 1

Gian Domenico Cassini discovered a large gap in Saturn's rings in 1675. Later, an astronomer named Encke discovered a smaller gap near the edge of the rings.

It was found long ago that an orbit in the Cassini Division, as the large gap is named, has a period almost exactly one-half that of one of Saturn's moons named Mimas. This means that every other time a chunk of ice orbits Saturn in the Cassini Division, it would see Mimas in the same position in the sky. Mimas has a pretty good mass, which means it has substantial gravity. Over millions of years, this periodic tug has yanked all the particles out of that region in Saturn's rings.

You notice a large gap between the A and B rings. This is called the "Cassini division". (See attached picture, where I've labeled the A, B, and C rings, along with the Cassini division.) There are other gaps in the rings at other places, but this one is the largest.

The Cassini division is caused by the pull of one of Saturn's moons called Mimas. A ring particle in the Cassini division would go around Saturn twice for every time Mimas goes around once; this is called a "2:1 resonance orbit". What happens is that if a ring particle were in the Cassini division, it would be pulled on by Mimas's gravity at the same place in its orbit every time Mimas passes by; the little gravitional "tugs" add up, just as pushing someone on a swing over and over makes the swing go higher. The gravitational tugs by Mimas eventually would pull the ring particle out of the Cassini division -- and that's why there's a gap there, with no ring particles inside.

below is image taken by NASA and Huble heritage team