Taylor

About

The average density of Ganymede, 1.936 g/cm3 (a bit greater than Callisto's), suggests a composition of about equal parts rocky material and mostly water ices. Some of the water is liquid, forming an underground ocean.

The mass fraction of ices is between 46 and 50 percent, which is slightly lower than that in Callisto. Some additional volatile ices such as ammonia may also be present. The exact composition of Ganymede's rock is not known, but is probably close to the composition of L/LL type ordinary chondrites, which are characterized by less total iron, 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.