This is an illustration of the interior of Jupiter's largest moon, Ganymede. It is based on theoretical models, in-situ observations by NASA's Galileo orbiter, and Hubble Space Telescope observations of the moon's aurorae, which allows for a probe of the moon's interior. The cake-layering of the moon shows that ices and a saline ocean dominate the outer layers. A denser rock mantle lies deeper in the moon, and finally an iron core beneath that.
