Facts on Saturn's Rings

1. They are are really, really thin. They are about 5 m thick and 300,000,000 m across.
2. There is a whole lot of stuff in the ring. The particles (a technical term) they are made of vary in size from 10 m to 1 cm. Or maybe smaller; that might just be the limit of the measurement. Lets assume the typical particle is 1 m across, giving it a mass of about 1000 kg. The total mass of Saturn's rings is about 3x10^19 kg. That would mean there were about 3x10^16 (30 quadrillion) particles. That is perhaps 100,000 times as many stars as there are in our galaxy.
3. Saturn's rings have their own atmosphere. That is different from Saturn's atmosphere. Its mostly oxygen, although its a little thin for humans Numbers are hard to find, but I think it is comparable to the best vacuum we can make on Earth.
4. The particles are spaced out pretty closely. On average, the space between them is about 3 times there diameter. That doesn't sound too close, but most of space is so empty we can see things in other galaxies. And its obviously thick enough to make the rings look solid.
5. There are a whole bunch of "moonlets" (i.e. very small moons) in Saturn's rings. They orbit with all the ring particles, so they stay in about the same place. In fact, it appear that the only difference between these moonlets and the normal ring particles is size. The moonlets are the ones big enough to stick out of the top and bottom of the ring at the same time.
6. Saturn has an extra ring (the Pheobe Ring) that much bigger and is tilted differently than the others. It also has a moon named Iapetus that is half black and half white. It turns out the Iaptus is half black because it keeps hitting the Pheobe Ring (which is black) and bits stick. Then the sun heats up the black bits and all the ice nearby melts and reforms on the white side, which is colder.
7. Saturn has a pair of what are called co-orbital moons named Epimetheus and Janus. That normally means that they are in the same orbit, which sometimes happens. But Epimetheus and Janus are weird. They are actually in slightly different orbits, but they periodically swap places!