The moon Pan lies in a gap in Saturn's A ring and Atlas lies just outside the A ring Image Credit: NASA/JPL/University of Colorado
Gaps In Saturn’s Rings Formed By Flying Saucer Moons
When one looks at Saturn, one is struck at how incredibly different it is to our Oblate Spheroid. It is truly spherical and it has a plate of material circling around it at it's equator. The plate, called rings, contains two very unique moons that are shaped like flying saucers.
The exploring satellite, Cassini, recently has given us clues as to how these moons were formed through its cameras.
The fact that the moons, Pan and Atlas are found in the gaps of the rings may give a clue to their unusual “flying saucer” shape.
This excerpted from the New Scientist -
Saturn's 'flying saucer' moons built of ring material
19:00 06 December 2007 - NewScientist.com news service, Maggie McKee
Saturn's moons Pan and Atlas may have formed in two stages - their cores may be remnants of the breakup of a large icy body early in the solar system's history and their ridges may have formed later, as the cores swept up material from Saturn's rings. The scenario might explain why the ridges appear smooth and the polar regions rough.
Two of Saturn's small moons look eerily like flying saucers, new observations by the Cassini spacecraft reveal. The moons, which lie within the giant planet's rings, may have come by their strange shape by gradually accumulating ring particles in a ridge around their equators.
Both moons have a flattened shape, being wider than they are tall. But their uncanny resemblance to UFOs only became clear recently, when Cassini viewed them with its powerful cameras.
The images revealed that the smooth ridges girdling the moons' equators lie in the same plane as Saturn's rings and are also as thick as the vertical distance that the moons appear to travel as they move through the rings.
An animation shows how Saturn's moons Pan and Atlas grew by sweeping up particles from Saturn's rings. Animation Video Credit: Courtesy of CEA/ANIMEA
Now, scientists led by Sébastien Charnoz of the University of Paris in France have run computer simulations suggesting that these ridges are made of material swept up from Saturn's rings.
The origin of the planet's famous rings is still a mystery. But one theory suggests that early in the solar system, one or more large, icy bodies broke up near the planet, creating detritus that then settled into flat rings.
If that is so, Pan and Atlas's cores may have been fragments of this breakup. After the rings flattened into a plane, ring particles may have fallen onto the moons, building up equatorial ridges. The ridges "could be considered as 'fossilised' accretion discs that once may have surrounded Pan and Atlas", the researchers write in the journal Science.
The process probably stopped long ago, since the moons' current orbits are thought to prevent the tenuous material still remaining around them to settle onto their surfaces.