Moons Meddle in Jupiter’s Aurora

Like Earth, Jupiter has auroras that gleam at its poles—a result of the planet’s magnetic field interacting with energetic particles streaming from the Sun. In recent years astronomers have noticed that Ganymede and Io, two of Jupiter’s moons, each add their own personal stamp to the planet’s auroras.

This ultraviolet image of Jupiter, taken with the Hubble Space Telescope Imaging Spectrograph (STIS), shows the main oval of the aurora, which is centered on the magnetic north pole, plus more diffuse emissions inside the polar cap. Auroral footprints can be seen in this image from Io (along the left hand limb), Ganymede (near the center), and Europa (just below and to the right of Ganymede's auroral footprint).
NASA/ESA, John Clarke (University of Michigan)

In this ultraviolet image from HST, Jupiter's aurora is visible. Jupiter's larger moons produce electric currents which interact with Jupiter's magnetic field, resulting in emissions that flow through the aurorae as the moons revolve around the planet.