Ganymede Moon Facts
jupiter moon ganymede
Natural color view of Ganymede.
  • Ganymede is the 7th moon in distance from Jupiter.
  • It is the largest moon in the solar system.
  • It has a diameter of 3,270 miles (5,262 km) which is larger than the planet Mercury.
  • Ganymede orbits Jupiter at a distance of 665,116 miles (1,070,400 km) and takes 7 days 3 hours to make one orbit of the planet.
  • It is the only moon in the solar system known to have its own magnetic field.
  • The moon has polar caps, possibly caused by ice interacting with plasma being funnelled down its magnetic field and creating a layer of frost.
  • Ganymede has a low density meaning that even though it is bigger than Mercury it only has half its mass.
  • Ganymede's low mass is as a result of water ice making around half its composition.
  • Jupiter's gravity pushes and pulls at the moon causing underground friction, possibly producing one or maybe even two layers of salty liquid oceans under its surface.
  • The moon was discovered in January 1610 by the Italian astronomer Galileo Galilei.

surface of ganymede
An image of impact craters on Ganymede's surface revealing the moon's icy crust.
Ganymede's Surface
Ganymede has two types of ancient surface, both of which have been unchanged for billions of years. Forty percent is made up of darker areas which are highly cratered. The remaining sixty percent consists of lighter areas marked by grooved terrains. Some of these grooves are over 700 meters (2,000 feet) in height and run for thousands of miles across its surface.
Ganymede's Atmosphere
Ganymede has an extremely thin atmosphere consisiting of dispersed oxygen molecules.
Ganymede's Temperature
Daytime temperatures on the surface average around -113C to -183C (-171F to -297F). At night temperatures plunge even further to around -193C (-315F).

Life on Ganymede
Where water exists on Earth we find life and the same could be said of Ganymede if the moon does indeed possess underground oceans. Proving this would be a very difficult task though as the layers of liquid would be very deep below the surface and covered with thick ice.
Origin of Name
Ganymede is named after a handsome mortal prince from Greek mythology who was abducted by Zeus to become cup-bearer to the gods.