Ganymede, Jupiter's largest moon, has long been suspected of harboring a subsurface ocean. Now, using the Hubble telescope to spy on its aurorae, scientists say they can confirm a salty ocean beneath its frozen crust.
Ganymede is the rare moon that generates its own magnetic field, creating observable aurorae that scientists used to infer the presence of a subsurface ocean.
Ganymede's Aurora, as spied by Hubble. Because the moon is also embedded in Jupiter's magnetic field, the friction causes the lights to "rock back and forth."
Scientists found that the aurorae on Ganymede did not "rock" as much as expected, leading to the conclusion that a subsurface ocean was present and inhibiting the effect.
Ganymede as observed from the Galileo spacecraft. The confirmed presence of a salty ocean on the moon will make it an instant source of increased interest for space geeks.
