Saturn's 'UFO' Moons

Strange flying-saucer-shaped moons embedded in Saturn's rings have baffled scientists studying images transmitted by the ESA's Cassini Spacecraft. New research suggests that the oddly shaped moons, Pan and Atlas, are born largely from clumps of icy particles in the rings themselves, a discovery that could shed light on how Earth and other planets formerd from the disk of matter that once surrounded our newborn sun.

Observations by NASA's Cassini spacecraft revealed the moons Atlas and Pan, each roughly 12 miles (20 kilometers) from pole to pole, have massive ridges bulging from their equators some 3.7 to 6.5 miles (6 to 10.5 kilometers) high, giving them the classic Earthly UFO appearance.

At first glance, one could assume that fast rates of spin might have stretched Atlas and Pan out into such unusual shapes, just as tossing a disk of pizza dough flattens it out. But astronomers discovered that each takes about 14 hours to complete a rotation -not nearly fast enough to cause the flattened, disk-like shape.

Carolyn Porco, a planetary scientist at the Space Science Institute in Boulder, Colo., and her colleagues suspected these peculiar moons could be formed mostly from Saturn's rings, rather than just from fragments produced in collisions of larger moons. The location of the ridges lined up precisely with the rings of icy particles in which they were embedded, findings which are detailed in the Dec. 6 issue of the journal Science.

After analyzing the shapes and densities of the moons from data captured by Cassini, Porco's team now finds Pan and Atlas appear to be mostly light, porous, icy bodies, just like the particles making up the rings. Computer simulations suggest one-half to two-thirds of these bizarre moons are made of ring material, piled up on massive, dense fragments of bigger moons that disintegrated billions of years ago after catastrophic collisions with one another.

Astrophysicist Sebastien Charnoz at University of Paris Diderot, the lead author of a related new study—also described in the Dec. 6 issue of Science, suggests that the Saturnian ice-clump moons elongated and bulged out into the flying-saucer shapes in the manner of  accretion disks, which "are found everywhere in the universe—around black holes, around stars, around Jupiter."

Charnoz added that understanding how the icy particles piled up to make these shapes could shed light on how matter in the protoplanetary disks of our Solar System that formed around our newborn sun could have clumped together to make planets.

Posted by Casey Kazan.

Story links:

http://space.newscientist.com/article/dn13014-saturns-flying-saucer-moons-built-of-ring-material.html
http://www.nasa.gov/mission_pages/cassini/media/cassini-051005.html
http://www.space.com/scienceastronomy/071206-saturn-moons.html

Comments

[dylan]

do you think that this shows a form of accelerated planetary growth being as ice is more "stickier" than other harder materials which would tend to defect similar material if it hasn't enough g to hold on to it?

[amanda challis]

hi this looks great