Callisto

Jupiter IV

Callisto Facts

• Callisto is the eighth of Jupiter's known satellites and the second largest:
  • distance from Jupiter: 1,883,000 km
  • diameter: 4800 km
  • mass: 1.08e23 kg
  Callisto is the outermost of the Galilean moons.

• Pronounced "ka LIS toh".

• Callisto was a nymph, beloved of Zeus and hated by Hera. Hera changed her into a bear and Zeus then placed her in the sky as the constellation Ursa Major.

• Discovered by Galileo and Marius in 1610.

• Callisto is only slightly smaller than Mercury but only a third of its mass.

• Callisto and Ganymede seem to be composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface. Titan and Triton are similar.

• Callisto's surface is covered entirely with craters. Some large ones are surrounded by a series of concentric rings which look like huge cracks but which have been smoothed out by eons of slow movement of the ice. The largest of these has been named Valhalla (picture 3). The surface is very old, like the highlands of the Moon and Mars.

• Valhalla is the most dramatic example of a multi-ring basin. These are thought to be the results of massive impacts. Other examples are Mare Orientale on the Moon and Caloris Basin on Mercury.

• Like Ganymede, Callisto's ancient craters have collapsed. They lack the high ring mountains, radial rays and central depressions common to craters on the Moon and Mercury.

• Another interesting feature is Gipul Catena, a long series of impact craters lined up in a straight line (picture 9). This was probably caused by an object that was tidally disrupted as it passed close to Jupiter (much like comet SL 9) and then impacted on Callisto.

• Unlike Ganymede, with its complex terrains, there is no evidence of tectonic activity on Callisto (picture 5). Callisto is a good reference for comparison with other more complex worlds.

Pictures

1. (above) Callisto in color 240k gif
2. Jupiter's moon Callisto 78k gif

3. Callisto Impact Scar Valhalla 61k gif; 60k jpg

4. High res view of Valhalla 794k gif

5. Callisto Impact Craters 105k gif; 148k jpg

6. another view of Valhalla 191k gif
7. Callisto with Narrow Angle Camera (No filter) 468k gif
8. Callisto with Narrow Angle Camera (No filter) 300k gif

9. Gipul Catena 117k gif
10. hires image of Callisto 2000k gif

More about Callisto

• from LANL
• from JPL

Open Issues

• Why are Callisto and Ganymede so different?
• Is Callisto's interior still liquid?