File:Auroras on Jupiter, Saturn, and Io (3239009082).jpg

This is a composite of three images showing auroras on astronomical bodies other than Earth.

The famous top image is the “spectacular NASA Hubble Space Telescope close-up view of an electric-blue aurora that is eerily glowing one half billion miles away on the giant planet Jupiter…Though the aurora resembles the same phenomenon that crowns Earth's polar regions, the Hubble image shows unique emissions from the magnetic "footprints" of three of Jupiter's largest moons. (These points are reached by following Jupiter's magnetic field from each satellite down to the planet).

“Auroral footprints can be seen in this image from Io (along the lefthand limb), Ganymede (near the center), and Europa (just below and to the right of Ganymede's auroral footprint). These emissions, produced by electric currents generated by the satellites, flow along Jupiter's magnetic field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.

“This ultraviolet image of Jupiter was taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on November 26, 1998.”

The bottom left image is “the first image of Saturn's ultraviolet aurora taken by the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST) in October 1998, when Saturn was a distance of 810 million miles (1.3 billion kilometers) from Earth…Saturn's auroral displays are caused by an energetic wind from the Sun that sweeps over the planet, much like the Earth's aurora that is occasionally seen in the nighttime sky. Unlike the Earth, Saturn's aurora is only seen in ultraviolet light that is invisible from the Earth's surface, hence can only be observed from space.”

The bottom right image contains an “eerie view of Jupiter's moon Io in eclipse (left) was acquired by NASA's Galileo spacecraft while the moon was in Jupiter's shadow. Gases above the satellite's surface produced a ghostly glow that could be seen at visible wavelengths (red, green, and violet). The vivid colors, caused by collisions between Io's atmospheric gases and energetic charged particles trapped in Jupiter's magnetic field, had not previously been observed. The green and red emissions are probably produced by mechanisms similar to those in Earth's polar regions that produce the aurora, or northern and southern lights. Bright blue glows mark the sites of dense plumes of volcanic vapor, and may be places where Io is electrically connected to Jupiter…The images were taken on May 31, 1998 at a range of 1.3 million kilometers (800,000 miles) by Galileo's onboard solid state imaging camera system during the spacecraft's 15th orbit of Jupiter.”

Image credits: Jupiter and Io: NASA-JPL Saturn: NASA-MSFC Composite Image: Image Editor