March 3, 2009--A faint pinprick of light embedded in one of Saturn's outermost rings is now the 61st moon known to be circling the giant planet, astronomers announced today.
Images taken by NASA's Cassini spacecraft over a 600-day stretch revealed the tiny moonlet moving in a partial ring known as a ring arc that extends about a sixth of the way around Saturn's faint G ring.
(Related: "Hubble Reveals New Moons, Rings Around Uranus.")
Based on its brightness, astronomers estimate that the as-yet-unnamed moon is a third of a mile (half a kilometer) wide. This is tiny as far as moons go, but the object is likely the largest in its neighborhood.
Researchers think meteoroid impacts as well as collisions among larger particles within the arc create clouds of dust that spread out to form the G ring.
"Being one of the bigger objects, the moonlet is likely to be hit more often," said Matthew Hedman, a member of the Cassini imaging team, based at Cornell University in Ithaca, New York. This means the moonlet is probably a significant source of ring material, the scientists say.
In the long term, "as this and other objects grind themselves down, it's conceivable they would disappear, and then the G ring would disappear," Hedman noted.
But it's also possible that other, slightly larger moons could be broken into chunks by bombardments, he added. Then, as with the moonlet, collisions with those chunks would generate dust that could cause existing rings to brighten or even new rings to form.