Tuesday, January 08, 2008
Saturn's extra-weird moons
Meet the craziest of the wacky, the weird moons of Saturn's panoply: Atlas and Pan.
In the December 7th 2007 issue of Science Sébastien Charnoz, André Brahic, Peter C. Thomas, and Carolyn C. Porco argue the equatorial ridges on these moons are a result of post-formation dumping. Pan sits in the Encke Gap in the A ring. Atlas is just outside the A ring. And it makes sense, too. They are in the outer regions of the ring system, the ridges are aligned with the Saturn ring plane, and that the kinematics would allow particles to preferentially land on the equators of these moons, plus the fact that they don't rapidly rotate (to dismiss a "frozen" rapid rotator), you can easily see this is an easy case.
Indeed, if you look at the Atlas image you can see how the central sphere is a rocky body, and the equatorial ridge is smooth, as if made of dusty particles.
One question not addressed in the paper is if Iapetus' equatorial ridge is similar in origin--others have attempted to use rapid rotation to explain that one, and it doesn't sit well when other satellites in the same system have ring-based ridges.
All of these images break my brain from the multiple viewing geometries.