Jupiter has Sixteen moons that can be divided into four groups.

I. Four inner small moons:

- Amalthea and Thebe rotate synchronously around Jupiter.

II. The Galelian Moons.

Io, Europa, Ganymede, and Callisto:
Io, Europa and Ganymede are locked together by tidal forces into a 1:2:4 orbital resonance.

III. Jupiter's Outer Moons

A. Leda, Himalia, Lysithea and Elara
B. Ananke, Carme, Pasiphae and Sinope

1. Retrograde orbits

Saturn's Satellites


1. Saturn has 18 named satellites
2. All moons but Phoebe and Hyperion rotate synchronously.
3. Moons with orbital resonence:

- Mimas-Tethys is in a 1:2 resonance;
- Enceladus-Dione is in 1:2
- Titan-Hyperion is in 3:4

4. Complex tidal resonances between some moons and the ring system:

- "shepherding satellites"
- Mimas seems to be responsible for the paucity or emptiness of material in the Cassini division.
- Basically the whole system is very complex and as yet poorly understood.

5. Janus and Epimetheus are "co-orbital".

6. Telesto and Calypso orbit in Tethys's Lagrange points (60 degrees ahead and behind Tethys in the same orbit).


- Helene is in Dione's leading Lagrange point.

7. All of Saturn's moons except for Phoebe and Iapetus orbit very nearly in the plane of Saturn's equator.

8. Phoebe's eccentric, retrograde orbit and unusual albedo indicates that it may be a captured asteroid or Kuiper Belt object.

9. The possability of 12 new moons was made posssble from views of the Hubble Space Telescope and Voyager 2. But it's believed that there are actually only 4 new moons and not 12. All doubt should be laid to rest with the arrival at Saturn of the Cassini spacecraft in 2004.

Uranus's Satellites
1. 15 known moons.

2. They all have nearly circular orbits in the plane of Uranus's equator (and hence at a large angle to the plane of the ecliptic).

3. They form two distinct classes:


A. 10 small very dark inner ones discovered by Voyager 2
B. and the 5 large outer ones.

Neptune's Satellites

1. 8 known moons

- 7 small ones and Triton.

2. Naiad, Thalassa, Despina and Galatea are all irregularly shaped.
3. Like Proteus, Larissa is irregular (non-spherical) in shape and appears to be heavily cratered.
4. Nereid's orbit is the most highly eccentric of any planet or satellite in the solar system