Images obtained by NASA’s Cassini probe orbiting Saturn suggest the presence of a nascent moon in one of the planet’s rings.
According to a NASA statement, the new images show perturbations along the outer edge of Saturn’s A ring, the outermost of the planet’s rings. One such disturbance occurs in an arc 20 percent brighter than the surrounding ring material, 750 miles long, and six miles wide.
The outer edge of the A ring, usually a smooth, sharply defined border, exhibits several strange bumps.
The perturbations and bumps are likely due to the gravitational effects of a small, previously undocumented object nearby. The object, informally dubbed Peggy, probably will not grow larger than it already has, and might be disintegrating already.
It is also possible that the object might be in the act of exiting the ring system and becoming a new moon of Saturn, which currently boasts a population of 62 moons. At no more than a half-mile wide, Peggy is too small to be imaged directly.
If Peggy does become a new Saturnian moon, it could well be the last; Saturn’s rings are very likely too depleted of material to create additional moons.
Observations of Peggy could reveal exactly how Saturn’s icy moons, such as Titan and Enceladus, formed from material in the rings, then migrated out through the rings, merging with other incipient moons along the way, and finally assumed their familiar orbits around Saturn.
Studying moon formation around Saturn could also serve as a proxy for investigating how the newly-formed planets formed and moved farther away from the Sun in the early evolution of our solar system.
Cassini’s orbit will bring it closer to the A ring in late 2016, affording a chance to examine Peggy in greater depth and maybe even image it directly.