Saturn’s Aviators Up Close

Saturn has aviators?  What?

Well, not really, no, but it does have propellers.  These strange structures were first spotted in Cassini imagery in 2006, but not conclusively identified until 2010, when the lighting conditions were right again.  They are now mapped well enough to confirm that they are not transient structures but persist over long timescales, long enough to justify giving them names.  Appropriately enough, they’re named for famous aviators from the early, propeller-driven days of aviation: Bleriot, Earhart, and Santos-Dumont are three that have been closely monitored.

This monitoring has allowed planetary scientists to confirm that they clumped ring particles being pulled along by moonlets embedded in Saturn’s ring (mainly in the A ring, in a region now known as “the propeller belt” because there are so many of them there).  With Cassini now moving closer to the rings than ever before, the propellers are being closely watched, as they represent a natural lab of planetary formation.

Here’s Earhart, photographed on March 22:

That black area to the right is the Encke Gap, which is shepherded by the moon Pan.  I blogged about Pan not too long ago, as Cassini recently revealed that it is shaped like a ravioli.  It’s a tiny little world, but it dwarfs the tiny moonlet in the middle of Earhart.  Pan is big enough to sweep the gap open, although it tugs and pulls as it goes, creating waves through the rings.  Earhart’s moonlet is much too small and the A-ring too dense; the moonlet displaces material, but it quickly slumps back in after the moon’s small gravity well passes.

Here’s Bleriot, which looks a bit different, although scientists aren’t sure whether that’s a real difference or just a difference in viewing conditions.

And here’s Santos-Dumas, in two images taken Feb 21.  This took advantage of Cassini’s motion and grabbed shots before and after periapsis, so the shot on top is from the sunlight side of the rings, and the bottom shot is from the backlit side:

The propellers are fascinating structures, and hopefully we’ll get more looks at them over the next few months, before Cassini’s mission ends.  If not, well, they’ll definitely be a hot target for any future Saturn missions, to see how they’ve evolved over time.


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