Ganymede,is the largest moon in Solar system. Ganymede is by far the largest moon and orbits around planet Jupiter with a diameter of 5,262 kilometers. It is bigger in size than some of the planets like Mercury and Pluto and would have easily been classified as a planet if it was orbiting the sun. It has its own magnetic field. Its discovery was made by Galileo Galilei the Italian astronomer on January 7, 1610. The satellite orbits around Jupiter at a distance of 1,0700,400 km and takes 7.1 days to complete one orbit. The surface of Ganymede has two types of terrains. It consists of lighter, younger areas and a darker cratered region. The planet’s atmosphere is thin and has oxygen contained in dispersed molecules. Water ice and rocky material make up the planet, and it thought to have underground oceans. The name is derived from a prince in Greek mythology.