Cassini Eyes Possible New Moon Forming In Saturn's Orbit
April 15, 2014

Cassini Eyes Possible New Moon Forming In Saturn’s Orbit

Brett Smith for - Your Universe Online

Newly released images from NASA’s Cassini probe have revealed the “birthing” of a tiny moon in orbit around Saturn.

The images, taken exactly one year ago on Tuesday, showed evidence of the formation of a tiny icy moon, named “Peggy” – according to a new report on the find in the journal Icarus. The study authors said the discovery could provide information about the formation of Saturn’s other moons as well as the process behind planet formation.

"We have not seen anything like this before," said study author Carl Murray of Queen Mary University of London. "We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right."

Cassini's images show disruptions on the very fringe of Saturn's A ring – the outermost from the planet's sizeable, bright rings. One disruption is an arc approximately 20 percent more brilliant than its surroundings, 750 miles long and 6 miles wide. Researchers also discovered unusual lumps in the generally smooth profile at the ring's edge. The study authors said the arc and lumps are attributable to the gravitational effects of an object in close proximity.

The researchers said they do not expect the object to grow any bigger, in fact – it may even be deteriorating. However, the process of its formation and outward motion supports our knowledge of how Saturn's icy moons, like the cloud-wrapped Titan and watery Enceladus, could have developed in more substantial rings long ago.

"Witnessing the possible birth of a tiny moon is an exciting, unexpected event," said Linda Spilker, a Cassini Project Scientist who was not among the study’s authors.

According to Spilker, the NASA probe’s orbit will shift closer to the exterior edge of the A ring in late 2016 – offering a chance to study Peggy in more detail and perhaps even capture pictures of it. Attempts to take pictures of the moon have been unsuccessful so far, as the new satellite is thought to be no more than about a half mile across.

Two primary factors are thought to have played a role in the analysis of Saturn's icy moons: size of the moons tends to increase as their proximity to the planet increases and the moons are mostly made of ice. Researchers currently suspect that the moons formed from icy ring particles and then shifted away from the planet – possibly combining with other moons on the way.

"The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons," Murray said. "As the moons formed near the edge, they depleted the rings and evolved, so the ones that formed earliest are the largest and the farthest out."

The study authors said it’s possible moon formation around Saturn has ended – with the rings mostly depleted of moon-forming materials. Because they may be seeing a completely unique event, the study team said they are trying to get every bit of information they can from the Cassini images.