ABSTRACT
Jupiter, the Giant Planet, has an impressive retinue of satellites. Most of them are small, but four - the so-called Galileans - are of planetary size and three of them are larger than our Moon, while one (Ganymede) is actually larger than the planet Mercury. All four have been imaged by the various space probes and each has provided its guora of surprises. But to set the scene, here are their main characteristics.
