Saturn has rings. How did it get them?

 

If you've read the novelization of 2001: A Space Odyssey by Arthur C. Clarke, you already know that the Saturnian rings are the leftover construction material from building the Stargate.  I'm sorry if that's a spoiler, but the movie (and the novel) came out in 1968.  

Now there's a different explanation, though I sure like the 2001 story.

How Saturn got its rings: Simulations suggest they evolved from the debris of two moons which collided a few hundred million years ago

"By simulating almost 200 different versions of the impact, the research team discovered that a wide range of collision scenarios could scatter the right amount of ice into Saturn's Roche limit, where it could settle into rings as icy as those of Saturn today.

Since other elements of the system have a mixed ice-and-rock composition, alternative explanations haven't been able to explain why there would be almost no rock in Saturn's rings.

The findings were published in The Astrophysical Journal."

And here's that paper.

A Recent Impact Origin of Saturn's Rings and Mid-sized Moons

A related article:

Saturn's Shiny Rings May Be Pretty Young