Surprise! Saturn has small moon hidden in ring

Scientists have found a new moon hidden in one of Saturn's dazzling outer rings.

The international Cassini orbiter spotted the moon, which measures about a third of a mile wide.

The discovery was announced Tuesday in a notice by the International Astronomical Union.

Researchers have long puzzled over the formation of Saturn's G ring, one of the planet's more mysterious arcs.

"Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd," Cornell University astronomer Matthew Hedman, a member of the Cassini imaging team, said in a written statement. "The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring."

The leading theory is that the G ring was formed from icy debris that scattered when meteorites crash into the newfound moon.

Scientists first identified the moon in Cassini imagery from last summer. Since then, they confirmed its presence by looking for it in earlier images and spotting it in pictures taken as late as last month. The moon is so small that its size cannot be measured directly; instead, its size was estimated by comparing it with another small Saturnian moon called Pallene.

The Cassini imaging team's leader, Carolyn Porco of the Space Science Institute, said in an e-mail that the new moon makes "number 61 for Saturn ... but who's counting!"

This report includes information from The Associated Press and msnbc.com.