Saturn's Small Moons

Saturn's innermost three moons are:

• Pan,
• Atlas and
• Prometheus.

Pan

• Pan (Saturn XVIII) is the innermost of Saturn's known satellites:
  • distance from Saturn: 133,583 km
  • diameter: 20 km
  a.k.a. 1981 S 13

• Pan was the god of woods, fields, and flocks, having a human torso and head with a goat's legs, horns, and ears.

• Discovered by Mark R. Showalter in 1990 from Voyager photos.

• Pan is within the Encke Gap in Saturn's A ring.

• Small moons near the rings produce wave patterns in the rings. Prior to the discovery of Pan, an analysis of the patterns in the edge of Saturn's A ring predicted the size and location of a small moon. Pan was discovered by reexamining the 10 year old Voyager photos at the predicted spot.

• It is likely that there are more moons within Saturn's rings yet to be discovered.

Pictures

1. (above) Pan 5k gif
2. Pan within the Encke Gap 54k gif

More about Pan

• from LANL
• 1990 NASA press release about the discovery of Pan

Atlas

• Atlas (Saturn XV) is the second of Saturn's known satellites:
  • distance from Saturn: 137,670 km
  • diameter: 30 km (40 x 20)
  a.k.a. 1980 S 28

• Atlas was a Titan condemned by Zeus to support the heavens upon his shoulders; son of Iapetus and the nymph Clymene; brother of Prometheus and Epimetheus.

• Discovered by R. Terrile in 1980 from Voyager photos.

• Atlas seems to be a shepherd satellite of the A ring.

Pictures

1. (above) Atlas 9k gif

More about Atlas

• from LANL

Prometheus

• Prometheus (Saturn XVI) is the third of Saturn's known satellites:
  • distance from Saturn: 139,350 km
  • diameter: 91 km (145 x 85 x 62)
  • mass: 2.7e17 kg
  a.k.a. 1980 S 27

• Pronounced "pra MEE thee us"

• Prometheus was a Titan who stole fire from Olympus and gave it to humankind, for which Zeus punished him horribly; son of Iapetus; brother of Atlas and Epimetheus. "Prometheus" is Greek for "foresight".

• Discovered by S. Collins and others in 1980 from Voyager photos.

• Prometheus is the inner shepherd satellite of the F ring.

• Prometheus has a number of ridges and valleys and several craters about 20 km in diameter but appears to be less cratered than the neighboring moons Pandora, Janus and Epimetheus.

• From their very low densities and relatively high albedos, it seems likely that Prometheus, Pandora, Janus and Epimetheus are very porous icy bodies. (Note, however, that there is a lot of uncertainty in these values.)

Pictures

1. (above) Prometheus 16k gif
2. Prometheus, moon of Saturn, little oblong moon 135k gif
3. Map of Prometheus 58k gif
4. Prometheus and the F ring 78k gif
5. Prometheus and Pandora and the F ring 79k gif

More about Prometheus

• from LANL

Open Issues

• What role do these moons play with respect to the rings?
• We know next to nothing about these moons. Even the basic mass and size data are not very accurate.
• Are Pan and Atlas similar to Prometheus in bulk properties?