Saturn has 60 named satellite bodies, or moons. Two of them, Pan and Atlas, are found within the boundary of Saturn’s famous rings— a place where it is almost impossible for moons to form. Not only that, but Pan and Atlas both have the same unusual shape, with a prominent ring at the equator that makes them look like flying saucers. How did these strange small moons come to be?

Two teams of scientists, led by Carolyn Porco of the Space Science Institute in Boulder, Colorado, and Sebastien Charnoz of the University of Paris, may have clues to an answer. The teams’ findings have been published in the December 6 issue of Science magazine. Porco and her colleagues have discovered that the equatorial ridges on Pan and Atlas are made up of an icy material that is very similar to the material of the rings themselves— leading them to the conclusion that the originally spherical moonlets gathered particles from the rings, which built up into ridges along the equator.
Charnoz and his associates elaborate in their paper on the precise process by which the accretion, or build-up, along the equator happens. Understanding this process may help scientists to better understand how the Earth and other planets in our solar system were formed from an early disk surrounding the equator of our sun.