Simplified view of the magnetic environment around Jupiter and its four largest moons: Io, Europa, Ganymede and Callisto. In reality the interactions are extremely variable and complex. ESA’s Jupiter Icy Moons Explorer, Juice, will investigate the magnetic environment in great detail, exploring the invisible connections between the moons and the giant planet to understand more about the interplay of this intensively dynamic system.

The animation begins with a short focus on Jupiter. The giant planet’s aurorae are displayed as a blue ring around the north and south polar regions, and its magnetic field lines are shown in dark purple throughout. The animation then moves through the key elements of the magnetic field situation at each of the moons.

Callisto, the outermost of the four large moons, is the first to be seen, showing the geometry of the magnetic field created within the moon’s putative subsurface ocean as the moon moves through Jupiter’s magnetic field.

The next sequence shows the Ganymede’s magnetic environment, which is a combination of an induced and internal magnetic field. Ganymede is unique in the Solar System in that it is the only moon known to generate its own magnetic field, which has complex interactions with Jupiter’s own vast magnetic field. Ganymede’s auroral ovals are illustrated in blue rings in the mid northern and southern latitudes; they are influenced by Jupiter’s magnetic field as well as the moon’s buried ocean.

Europa is represented next, with its magnetic field created within its subsurface ocean.

Io, the innermost of the four large moons, is illustrated with vertical magnetic field lines connecting to Jupiter. Io is a volcanic moon, and its thin sulphur dioxide atmosphere generates an ionized plasma torus around Jupiter, seen as the hazy yellow ring.

Zooming out, the final sequence shows Jupiter and its large moons, as well as the Io torus, created by the ionization of the volcanic moons’ atmosphere.

Jupiter and its four large moons are often considered as an archetype for a solar system in their own right. Thus Juice’s investigations of the moons and their interactions with Jupiter will provide unique insight into the numerous exoplanet systems that have been discovered elsewhere in the Universe.