Cassini sees disturbances rippling through the ring's icy expanses

Apr 15, 2014 15:01 GMT  ·  By
Cassini sees the potential formation of a new moon on the outer edge of Saturn's A Ring
   Cassini sees the potential formation of a new moon on the outer edge of Saturn's A Ring

Mission controllers at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, California, say that the Cassini spacecraft is currently observing a series of disturbances in the outermost of the large, bright rings around Saturn, the A Ring. According to planetary scientists, we could be witnessing the formation of a new Saturnine moon from the debris that makes up this ring. 

According to previous measurements made by Cassini, the A Ring is between 10 and 30 meters (34 to 100 feet) thick and has a mass roughly similar to that of the small moon Hyperion. The shape and boundaries of the ring are maintained by a 7:6 orbital resonance interference pattern between the moons Janus and Epimetheus.

A series of other resonance patterns produces spiral density waves within the structure of the A Ring, which are far more pronounced here than in other rings. Astronomers say that these waves are similar in behavior to the spiral arms of galaxies. These patterns of interaction may be one of the potential sources triggering the formation of a new moon at the ring's outer boundary.

Cassini is keeping a close eye on the small icy object that appears to be developing at this location. Experts say that studying this process up close could reveal a host of new data on how other moons formed around the gas giant.

“We have not seen anything like this before. 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,” explains Queen Mary University of London investigator Carl Murray. He is the lead author of a new paper detailing the findings, published in the April 14 online issue of the astronomical journal Icarus.

Cassini first started observing the creation of the new moon on April 15, 2013. An unusual protuberance was observed at the time, spanning a length of 1,200 kilometers (750 miles) and a width of around 10 kilometers (6 miles). This structure is now believed to be caused by gravitational interactions with a nearby object, researchers say in the new paper.

The object, informally known as Peggy, is too small for Cassini to see, but it is not expected to grow any larger. In fact, the team estimates, it may already be falling apart. However, keeping an eye on this situation is important because it may reveal more insight into how moons such as Titan and Enceladus formed. Similar processes may have occurred when the inner rocky planets formed.

“The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons. 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,” Murray explains.

“Witnessing the possible birth of a tiny moon is an exciting, unexpected event,” comments JPL investigator and Cassini project scientist Linda Spilker. She adds that Cassini will move in an orbit closer to the outer edge of the A ring in late 2016. At that time, scientists will get the opportunity to see Peggy and study it, if the object endures.