Saturn's saucer moons

The highest resolution images of Pan and Atlas reveal distinctive “flying saucer” shapes created by prominent equatorial ridges not seen on the other small moons of Saturn.

From left to right: a view of Atlas' trailing hemisphere, with north up, at a spatial scale of about 1 km/ pixel; Atlas seen at about 250 m/per pixel from mid-southern latitudes, with the sub-Saturn hemisphere at the top and leading hemisphere to the left; Pan's trailing hemisphere seen at about 3 km per pixel from low southern latitudes; an equatorial view, with Saturn in the background, of Pan's anti-Saturn hemisphere at about 1 km per pixel.

On Atlas, the ridge extends 20 to 30° in latitude on either side of the equator; on Pan, its latitudinal extent is 15 to 20°. Atlas shows more asymmetry than Pan in having a more rounded ridge in the leading and sub-Saturn quadrants.

The heights of the ridges can be crudely estimated by assuming (ellipsoidal) shapes that lack ridges and vary smoothly cross the equator. Heights of Atlas' ridge range from about 3 km at 270° west to 5 km at 180° and 0°. Pan's ridge reaches about 4 km at 0° west, and is about 1.5 km high over most of the rest of the equator.

The ridges represent about 27% of Atlas' volume and 10% of Pan's volume.

The images were acquired with the Cassini spacecraft narrow-angle camera between 2005 and 2007. Pan is 33 km across at its equator and 21 km across at its poles; Atlas is 39 km across at its equator and 18 km across at its poles.