I also put the image in front of high school students via a DLP in a darkened classroom. They might not have been as jazzed about the shot as I was, but that’s more a matter of me being completely awestruck and transfixed.

Thanks BA!

You mean this is a temporary phenomenon? Oh, okay. No need for an Earth-shattering kaboom, then.

Saturn isn’t a perfect sphere. It’s spin makes it bulge at the equator. In fact, it bulges enough that you can even see it in the pictures above: Saturn has a bad case of middle-age spread.

But this has a neat affect on the orbits of anything going around Saturn. A circular orbit along the equator doesn’t change much over time. But if you give that orbit a little tilt, it starts doing things that Kepler never imagined: it precesses. In other words, the plane of the orbit twists slowly over time.

The reason this is a problem is that the rate of twisting changes depending on how far you are from the center of the planet. So imagine a ring tilted in comparison to the equator. A little while later, the inner part of the ring has twisted 80 degrees in comparison to where it started, while the outer part has only twisted 60 degress. The whole thing is shearing apart, and soon different parts of the ring are crashing into each other.

Now we’re back to the problem that Jon described, with all of the pieces colliding until it’s all down in one plane: the plane of the equator.

So that’s why Saturn (and all of the other giant planets) have rings that are directly over their equators.

Isn’t planetary dynamics fun?

Why isn’t it possible though for two rings at different radii to orbit in different planes (at an angle to each-other)?

I also want to make one small correction to Jon Niehof’s otherwise fine explanation of the flattening of the rings: it really is collisions that damp down the motions, not just gravitational interactions. Those ring particles really are hitting each other. The timescale of collisions for a particle that isn’t in the ringplane is on the order of the optical depth (how easily can you see through it) times the orbital period.

If it was really just gravitational, then you would get a kind of equipartition with the larger particles forming a really thin layer while the smaller ones get scattered farther out of the plane.

This has been another good week in space exploration. First the MRO shots of Victora crater, the inside of the crater from Opportunity, and now this!
DANG! Awesome, awesome….

Tom