Images from NASA's Cassini spacecraft taken Apr. 15 hint at the formation of a new Saturnian moon. The icy object, believed to be only half a mile in diameter, recently formed in Saturn's outer rings and has been given the provisional name, Peggy.
Scientists discovered the creation of the new moon when they detected disturbances in Saturn's outer ring, also known as the A ring. Using Cassini's narrow angle camera, the NASA team was able to detect an arc measuring 750 miles (1,207 k) in length that was roughly 20 percent brighter than the surrounding ring matter. Unusual protrusions were also detected along the ordinarily smooth edge of A ring, leading scientists to conclude that these irregularities were caused by the gravity of a nearby body, too small to be observed directly via telescope, distorting the shape of the outer ring.
Saturn hosts 62 confirmed moons, however very few are of any significant size or interest. Peggy is neither large, nor particularly unusual in composition, instead her significance lies in the fact that she may well be the last of Saturn's moons. NASA scientists believe that due to Peggy's meager size, and the prediction that it will grow no larger, Saturn's rings may now be too depleted to create any more moons, postulating that the rings we observe today are a mere shadow of their former glory.
"The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons," states Carl Murray, Professor of Mathematics and Astronomy at Queen Mary University, London, and lead author of the report on the findings. "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."
Therefore further observations of Peggy may help to shed light on the formation of Saturn's existing moons. Researchers have recently proposed, via an analysis of the composition of the planet's moons and the ring matter itself, that moons were formed in the parent planet's rings before moving outward, merging with other moons until they achieved a stable orbit. By observing Peggy over the coming years, hypotheses such as this one may be proved or debunked, either way increasing our knowledge and understanding of the Saturnian moons.
NASA's findings regarding Saturn's new moon have been published in the Icarus journal.