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.
An image of impact craters on Ganymede's surface revealing the moon's icy crust.
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 has an extremely thin atmosphere consisiting of dispersed oxygen molecules.
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.
Missions to Ganymede
JUICE (JUpiter ICy moon Explorer)
Launch: 2022 Arrival: 2030 Agency: ESA (European Space Agency) Summary: The JUICE probe will study the Jovian system, focusing on the icy moons of Europa, Callisto and Ganymede, investigating any potential habitable environments. The probe will enter into orbit around Ganymede in the latter part of the mission, studying its icy surface and subsurface ocean.
It will also observe how Ganymede's magnetic field interracts with Jupiter's magnetosphere.
Launch: January 2006 Arrival: January 2007 Agency: NASA Summary: As well as sending back images New Horizons made topography and composition maps of Ganymede.
Launch: October 1989 Arrival: December 1995 Agency: NASA Summary: Galileo made several flybys of Ganymede sending back a whole host of new data. As well as discovering a magnetic field, an ocean underneath its
surface was also detected. Galileo also sent back some stunning close up images of the moon.
Voyager 1 and 2
Launch: August-September 1977 Arrival: April-August 1979 Agency: NASA Summary: Voyager 1 and 2 made successful flybys of Ganymede taking far more detailed images than the previous Pioneer missions. The grooved terrain could be
seen and it was also revealed that Ganymede was in fact larger than first thought, replacing Saturn's moon Titan as the largest satellite in the solar system.
Pioneer 10 and 11
Launch: March 1972 - April 1973 Arrival: December 1973 - December 1974 Agency: NASA Summary: Pioneer 10 and 11 made successful flybys of Ganymede but only sent back limited data and blurry images such as the one on the left.