You asked:

Why does Saturn have rings? Why don’t the rocks in the ring attract each other and form a moon? — Simal, Sacramento, CA

Marshall Brain answers:

The fact that Saturn has rings has to do with something called the Roche limit or the Roche radius. If an object is orbiting a planet inside the Roche radius, it will tend to get pulverized into small bits by tidal forces, and it will never have the chance to coalesce. Eventually the bits fall out of orbit and hit the planet.

So Saturn’s rings could have come from a celestial object that was captured by Saturn’s gravity and started orbiting the planet like a moon would. But because the object was inside the Roche radius, it got pulverized and turned into the rings. Or perhaps two objects collided in orbit. Or the rings could be leftover material from the planet’s creation. These particles will never come back together because of the Roche limit.

See also:

See also: Surprising, Huge Peaks Discovered in Saturn’s Rings