Cassini observations reveal dynamic Saturn

We often talk about the solid bodies of the solar system as being dynamic - dust storms on Mars, jets on Enceladus, volcanoes on Io; it's less often that we say the same about our giant neighbors.  Recent images returned by the Cassini spacecraft remind us that the out planets are also constantly in flux.

Saturn's nearly-perfect hexagon is one of the most beautiful sights in the solar system.  (Image credit: NASA)

Saturn's nearly-perfect hexagon is one of the most beautiful sights in the solar system.  (Image credit: NASA)

First up is one of the most puzzling atmospheric features in the entire solar system - Saturn's North Polar Hexagon.  Jupiter may have its Great Red Spot, but on no other planet can one find such a remarkably geometric feature.  And most astonishing of all is that this formation is at least thirty years old!  It was first observed by the Voyager mission in the early 1980s and continues to this day.

How does such a wacky feature form?  It's not a settled debate but similar features have been created in the laboratory.  In those experiments hexagonal shapes (as well as octagons and other geometric designs) were created by rotating fluids at different rates.  Where these fluids came in contact, the hexagon was formed.  At Saturn, this likely means that winds of different speed in the upper atmosphere are coming together.  And the scale is huge: you could comfortably fit an Earth on each side of the hexagon!

Saturn's moon Prometheus stirs up the volatile F ring.  (Image credit: NASA.  Animation credit: Jason Major)

Saturn's moon Prometheus stirs up the volatile F ring.  (Image credit: NASA.  Animation credit: Jason Major)

Not dynamic enough for you?  How about this animation revealing the interaction between Saturn's tenuous F ring and nearby moon Prometheus.  Not quite on a circular orbit, Prometheus on skirts right into the edge of the F ring, where it causes gravitational disruption.  In the above animation, you can see the moon's approach yank material out of the ring and launch would looks reminiscent of a boat wake behind it.

Saturn's F ring sits right on the edge of what scientists call the Roche Zone.  Inside of this region, the gravitational pull of Saturn is too strong to allow new moons to form.  Outside the zone, moons can form and Saturn has formed more than 60.  The area within the Roche Zone, however, is extremely turbulent, as clumps of material form and dissolve in an unending dance.  It's believed that interactions with Prometheus play an important role in this process.

While none of these recent observations revealed previously-unknown phenomena, they serve as reminders of the solar system's constant state of flux, and the beauty that can result.