Jupiter's Moon Gannymede
More details below:
Size & Distance
* the largest moon in our solar system and the only moon with its own magnetic field.
* the only moon in our solar system bigger than the planet Mercury.
* Ganymede is 2.4x smaller than Earth. Circumference 10,272 miles. (Earth's Data)
* Ganymede has three main layers. A sphere of metallic iron at the center (the core, which generates a magnetic field), a spherical shell of rock (mantle) surrounding the core, and a spherical shell of mostly ice surrounding the rock shell and the core.
* The ice shell on the outside is very thick, and about 500 miles (800 kilometers) thick.
* The surface is the very top of the ice shell. Though it is mostly ice, the ice shell might contain some rock mixed in.
* Ganymede's magnetic field is embedded inside Jupiter's massive magnetosphere.
* The subterranean ocean is thought to have more water than all the water on Earth's surface.
Atmosphere / Weather
* magnetic field causes auroras, which are ribbons of glowing, electrified gas, in regions circling the moon’s north and south poles. (see illustration below)