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Saturn's moons and rings mix it up

NASA / JPL-Caltech / SSI

Saturn's rings stretch in front of the moons Titan and Tethys in a Dec. 7 image captured by NASA's Cassini orbiter.



What do you get when you cross the rings and moons of Saturn? That sounds like the set-up for a joke, but for the team that processes the pictures from NASA's Cassini orbiter, the answer is totally serious: You get stunning images of the moons' interplay with the giant planet's rings.


The picture above, released today, shows Saturn's rings nearly edge-on, in front of the moons Titan (left) and Tethys (right). Cassini's narrow-angle camera captured the view on Dec. 7, 2011, as it was flying by a distance of about 1.4 million miles from icy Tethys (TEETH-iss) and 1.9 million miles from smog-covered Titan.

Last week the Cassini imaging team released another stunner snapped on the same day, showing tiny Tethys (660 miles wide) near the center of Saturn's disk, just below the ring plane.

Cassini was so close to Saturn's equator that the rings look like little more than a straight line, but you can see the delicate shadows of the rings stretching across the planet's sunlit disk into darkness. When Cassini's wide-angle camera took this picture, Tethys was about 1.1 million miles away.

Saturn, with a diameter of 74,900 miles, overwhelms Tethys in size. But the gas giant's density is such that it could float in water — that is, if there were a body of water big enough for it to float in. Does that mean Saturn could take a bath? Yes ... but it might leave a ring.

NASA / JPL-Caltech / SSI

The Saturnian moon Tethys is dwarfed by the ringed planet's disk in this Dec. 7 picture from the Cassini orbiter.

More imagery from Cassini and other space probes:


Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding the Cosmic Log Google+ page to your circles. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.