Ganymede

Jupiter III

Ganymede Facts

• Ganymede is the seventh and largest of Jupiter's known satellites:
  • distance from Jupiter: 1,070,000 km
  • diameter: 5262 km
  • mass: 1.48e23 kg
  Ganymede is the third of the Galilean moons.

• Pronounced "GAN uh meed".

• Ganymede was a Trojan boy of great beauty whom Zeus carried away to be cupbearer to the gods.

• Discovered by Galileo and Marius in 1610.

• Ganymede is the largest satellite in the solar system. It is larger in diameter than Mercury but only about half its mass. Ganymede is much larger than Pluto.

• Ganymede and Callisto seem to be composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface (picture 8). Titan and Triton are similar.

• Ganymede's surface is a roughly equal mix of two types of terrain: very old, highly cratered dark regions (picture 5), and somewhat younger (but still ancient) lighter regions marked with an extensive array of grooves and ridges (picture 4). Their origin is clearly of a tectonic nature, but the details are unknown. In this respect, Ganymede may more similar to the Earth than either Venus or Mars.

• Similar ridge and groove terrain is seen on Enceladus, Miranda and Ariel. The dark regions are similar to the surface of Callisto.

• Extensive cratering is seen on both types of terrain. The density of cratering indicates an age of 3 to 3.5 billion years, similar to the Moon. Craters both overlay and are cross cut by the groove systems indicating the the grooves are quite ancient, too.

• Unlike the Moon, however, the craters are quite flat, lacking the ring mountains and central depressions common to craters on the Moon and Mercury. This is probably due to the relatively weak nature of Ganymede's icy crust which can flow over geologic time and thereby soften the relief (picture 6).

• Galileo's first flyby of Ganymede discovered that Ganymede has its own magnetic field embedded inside Jupiter's huge one.

Pictures

1. (above) Ganymede color 192k gif

2. Limb of Ganymede 78k gif; 84k jpg

3. Impact crater (mosaic of hi res images) 434k gif; 2014k gif

4. Close up Tectonic Patterns 74k gif; 106k jpg

5. Halo Crater 137k gif; 97k jpg

6. Ancient Terrain 174k gif; 77k jpg

7. Southern Galileo regio 400k gif

8. Color composite of Ganymede 42k jpg
9. diagram of Ganymede's interior 109k gif

10. first Ganymede images from Galileo html; (alt site html)

11. Ganymede with Narrow Angle Camera (Orange filter) 403k gif
12. Ganymede with Wide Angle Camera (Blue filter) 248k gif
13. Ganymede with Narrow Angle Camera (No filter) 385k gif
14. Ganymede with Wide Angle Camera (Green filter) 292k gif
15. Ganymede with Narrow Angle Camera (No filter) 487k gif
16. Ganymede with Narrow Angle Camera (No filter) 554k gif
17. Ganymede with Narrow Angle Camera (No filter) 560k gif
18. Ganymede with Wide Angle Camera (Orange filter) 331k gif
19. global view from Galileo 47k jpg (caption)
20. hi-res Galileo image 45k jpg (caption)

Movies

1. Flight over Ganymede 3300k AVI

More about Ganymede

• from LANL
• from JPL
• HST detection of ozone on Ganymede
• Fact sheet from the Galileo mission pages

Open Issues

• What processes created the light ridge and groove terrain?
• Why are Ganymede and Callisto so different?