Moons of Jupiter around Ganymede. In 2016, the "Juno" spacecraft imaged the Galilean moons from above their orbital plane as it approached Jupiter orbit insertion, creating a time-lapse movie of their motion. Moons of Jupiter There are 79 known moons of Jupiter. This gives Jupiter the largest number of moons with reasonably stable orbits of any planet in the Solar System. The most massive of the moons are the four Galilean moons, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. From the
Ganymede (moon) less metallic iron and more iron oxide than H chondrites. The weight ratio of iron to silicon ranges between 1.05 and 1.27 in Ganymede, whereas the solar ratio is around 1.8. Ganymede's surface has an albedo of about 43%. Water ice seems to be ubiquitous on its surface, with a mass fraction of 50–90 %, significantly more than in Ganymede as a whole. Near-infrared spectroscopy has revealed the presence of strong water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 μm. The grooved terrain is brighter and has a more icy composition than the dark terrain.