It also found that Ganymede, the largest moon in the solar system, has a magnetic field.

ECONOMIST: Galileo and Jupiter

It will be able to orbit Europa, Callisto and Ganymede individually, hopping from one to another.

ECONOMIST: Galileo and Jupiter

The existence of a magnetic field on Ganymede, the biggest moon of Jupiter.

CNN: Galileo moves on to Europa

Metallic cores in Europa, Io and Ganymede, but no such core in Callisto.

CNN: Galileo moves on to Europa

Now the technique used earlier this year to demonstrate the existence of the Europan ocean has been employed to detect an ocean on another Jovian satellite, Ganymede, according to work announced at the recent American Geophysical Union meeting in San Francisco.

ECONOMIST: Blue moon

And water would be all the more exciting on Ganymede because it is the largest moon in the solar system (larger even than the planets Mercury and Pluto) and, like earth, it has a permanent magnetic field that protects part of its surface from bombardment by certain sorts of life-destroying radiation.

ECONOMIST: Blue moon