Scientists from NASA’s Cassini mission are intrigued by the likely presence of a previously undetected small icy body within the rings of Saturn, the sixth planet from the Sun.
This image, taken with the Cassini’s narrow angle camera on April 15, 2013, shows an extended object 10 km beyond the edge of the Saturn’s A ring. Image credit: Carl D. Murray et al.
On images of the Saturn’s A ring, taken with Cassini spacecraft in April 2013, the researchers found few disturbances at ring’s very edge. One of these disturbances is an arc about 1,200 km long and 10 km wide.
The scientists also found unusual protuberances in the usually smooth profile at the ring A’s edge. They believe the features are caused by the gravitational effects of a nearby object.
“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,” said Dr Carl Murray of Queen Mary University of London, who is the lead author of the paper appearing in the journal Icarus.
The newly discovered object, dubbed Peggy, is probably no more than 1 km in diameter.
“Witnessing the possible birth of a tiny moon is an exciting, unexpected event,” said Dr Linda Spilker, a Cassini team member from NASA’s Jet Propulsion Laboratory in Pasadena.
“Cassini’s orbit will move closer to the outer edge of the A ring in late 2016 and provide an opportunity to study Peggy in more detail and perhaps even image it.”
It is possible the process of moon formation in Saturn’s rings has ended with Peggy, as Saturn’s rings now are, in all likelihood, too depleted to make more moons.
“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,” Dr Murray said.
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Carl D. Murray et al. The discovery and dynamical evolution of an object at the outer edge of Saturn’s A ring. Icarus, published online March 28, 2014; doi: 10.1016/j.icarus.2014.03.024
