Ganymede (moon) Ganymede. By definition, Anat is at 128° longitude. The 0° longitude directly faces Jupiter, and unless stated otherwise longitude increases toward the west. Ganymede appears to be fully differentiated, with an internal structure consisting of an iron-sulfide–iron core, a silicate mantle and outer layers of water ice and liquid water. The precise thicknesses of the different layers in the interior of Ganymede depend on the assumed composition of silicates (fraction of olivine and pyroxene) and amount of sulfur in the core. Ganymede has the lowest moment of inertia factor, 0.31, among the solid Solar System bodies. This is a consequence
Moon to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61 years, which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws. The Moon is exceptionally large relative to Earth: Its diameter is more than a quarter and its mass is 1/81 of Earth's. It is the largest moon in the Solar System relative to the size of its planet, though Charon is larger relative to the dwarf planet