The birth of a new moon has astronomers everywhere cooing over momma Saturn. Saturn has produced a big family, with “Peggy” coming in at number 63.
Officially, Peggy is too premature to be considered a moon. She’s “in the womb” still growing from inside Saturn’s rings. Right now the baby moon clocks in at 750 miles long and six miles wide. While that sounds large, it’s miniscule compared to the usual size of moons. Around Saturn moons can grow as large or larger than planets. Moons themselves are just orbiting satellites around larger objects with stronger gravity fields. This is the first time an event like a moon being born has been observed, making Peggy very special indeed.
She got the attention of astronomers after the Cassini spacecraft sent back some black-and-white images of the outermost ring. Peggy showed up as a spec 20 percent brighter than her surroundings. The baby moon looks like a lump on the edge of Saturn’s ring. She’s expected to be a moon made entirely of ice. “Witnessing the birth of a tiny moon is an exciting, unexpected event,” said Linda Spilker of Nasa’s Jet Propulsion Laboratory (JPL). The observation brings new insight into Saturn’s moons, which are mostly formed of ice. Titan, Saturn’s largest moon, is even considered to have an ocean of ice beneath it’s mountains. The prevailing theory from Peggy’s observation is that Saturn’s rings act as a kind of nursery for moons. Is it possible that at one time even Titan was nestled in Saturn’s icy rings? Or that the giant ‘absorbed’ smaller ice moons?
Prof Murray, a Cassini imaging scientist, reported that, “the rings are icy, more than 90% pure water-ice, so with the particles colliding you have the ideal conditions for objects to accrete, for objects to form in this region, and images do show this kind of clumpiness”.
The moon birthing process is a brutal one, with constant threat of elimination. The debris in Saturn ‘s “womb” means constant bombardment for the new moon. And, if Peggy survives the rings she’ll be born into an equally dangerous space. Her relatively large size within the rings protects her, but she’s a spec against Saturn’s larger moons. Over time – a lot of time – it’s possible that she might grow into a recognizable moon. The baby moon is too small to be tracked by scientists after she leaves the ring, but in 2016 the Cassini spacecraft’s orbit will bring more details to Peggy’s progress.