Wednesday, October 7, 2009

Newsflash! Saturn Has a Massive Ring Around It!

No, really. Check out the photo.

The mass of the ring begins 3.7 million miles outside that of the inner ring system we're all familiar with, and the density of the ice crystals and dust is so low that no one's ever noticed it before. But "the cool dust -- about 80 Kelvin (minus 316 degrees Fahrenheit) -- glows with thermal radiation. NASA's Spitzer Space Telescope, used to spot the ring, picked up on the heat."

The ring is also tilted at an angle with respect to Saturn and the inner ring. The CNN article says:

One of Saturn's moons, Phoebe, orbits within the ring. As Phoebe collides with comets, it kicks up planetary dust. Scientists believe the ice and dust particles that make up the ring stems [sic] from those collisions.

This suggests that the newly discovered outer ring follows Phoebe's orbit -- that they're of similar size and tilt. I tried to find confirmation of this, but the Google-fu failed me. I found a couple of graphics showing Phoebe's orbit, but can't tell whether the tilt matches that of the outer ring. I suppose it makes sense that something discovered this recently wouldn't have generated all sorts of comparative diagrams yet.

It makes me wonder how this works, though. If Phoebe actually did create the outer ring, by smacking into comets over a long period of time, then why doesn't every moon have an associated ice-and-dust ring? There are cometary paths all over the solar system, and over however many millions of years, one would think there'd have been time for other moons to smack into their own comets and form ring systems.

Maybe other moons do have other rings in their orbits and we just haven't pointed the right types of cameras at the right angles to find them yet.

If they don't, then why not? What's special about the Saturn-ring-moons-Phoebe-bigger-ring system that it happened there and not elsewhere? For that matter, why does Saturn have the inner, more visible ring system at all, while none of the other planets do? Other planets do have rings, but only tiny, dull fractions of Saturn's. Saturn is less than 30% Jupiter's mass, so it's not that its mass draws in lots of space junk and none of the other planets are massive enough to do so.

Stuff like this always renews my interest in solar-system based SF, though; new discoveries always add to the "What if?" lists. :)


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