File:Voyager 1 Image of Ganymede - GPN-2003-000007.jpg

English: Voyager 1 took this picture of Ganymede from a distance of 1.6million miles. Ganymede is Jupiter's largest satellite with aradius of approximately 2600 kilometers, about 1.5 times thatof Earth's Moon. Ganymede is the seventh and largest ofJupiter's known satellites and is the third of the Galileanmoons. Discovered in 1610 by Galileo and Marius, Ganymede is the largest satellite in the Solar System. It was named after theGreek mythical character, Ganymede, a handsome Trojan boy that Zeus took to Olympus to be a cupbearer for the gods(one of the only humans in Greek mythology who became immortal). Ganymede is larger than Mercury but has only halfMercury's mass. It has a bulk density of only two gramsper cubic centimeter, almost half that of Earth's Moon. Ganymede is most likely composed of a mixture of rock and ice. The long white filaments resemble rays associated with impactson the lunar surface. The various colors of different regionsprobably represent differing surface materials. Several dots of a single color (blue, green, and orange) on the picture arethe result of markings on the camera used for pointing determinations and are not physical markings. Voyager scientists discovered that Ganymede has its own magnetosphereembedded inside Jupiter's large one. JPL manages and controlsthe Voyager Project for NASA's Office of Space Science.