In pictures like the one above, it might look like Saturn’s moon, Mimas, is crashing its way through the rings. It’s actually orbiting about 28,000 miles (45,000 kilometers) above the rings. However, this doesn’t mean that Mimas isn’t affecting the rings through its gravitational pull, which is actually high enough to make waves in Saturn’s rings that can be seen in some images taken by Cassini.
Mimas is about 246 miles (396 kilometers) across, which may not seem all that big in astronomical terms. However, you may remember from science class that anything that has mass also has a gravitational pull, albeit not that large of one in a lot of cases. This means that the chair you are sitting in is exerting a force on you (and you on it), but its gravitational force is not large enough to be an excuse for not standing up and stretching every once in a while. Because Mimas is many times larger than the chair, it has a proportionately higher gravitational pull that is enough to affect Saturn’s rings.
Besides the waves, Mimas’ gravity had an influence in creating the Cassini Division between Saturn’s two outermost primary rings, the A and B rings. The Cassini Division is the widest of several gaps between Saturn’s rings at an average of 4,800 kilometers across. Although the Voyager probes had previously photographed the rings during their flyby of Saturn, the Cassini probe has sent back higher-resolution photographs that revealed more detail. The Cassini Division is not even completely void of features such as smaller ringlets that range from 6 to 50 kilometers wide.
Cassini has revealed a surprisingly complex structure in Saturn’s rings that wasn’t possible for the Voyager probes to expose with their less sophisticated cameras. It’s even been theorized that some of the features of Saturn’s rings are the result of undiscovered moonlets or asteroids passing through the rings or close enough to the rings that their gravity has an effect.Mimas is just one of several moons that are having a direct effect the rings of Saturn, including making waves.