Chandra X-ray Image of Jupiter
In preparation for New Horizon's approach, Chandra took exposures of Jupiter on February 8, 10, and 24th, 2007. The purpose of the Chandra observations is to study the powerful X-ray auroras observed near the poles of Jupiter. These are caused by interaction of sulfur and oxygen ions in the outer regions of the Jovian magnetic field with particles flowing away from the Sun in the so-called solar wind. Scientists would like to better understand the details of this process, which produces auroras up to a thousand times more powerful than similar auroras seen on Earth.
(Credit: NASA/CXC/SwRI/R.Gladstone et al.)

Hubble Optical Image of Jupiter
NASA's Hubble Space Telescope took this view of Jupiter in support of the New Horizons Mission. The image was taken with Hubble's Wide Field Planetary Camera 2 on February 17, 2007, using the planetary camera detector. Jupiter's trademark belts and zones of high- and low-pressure regions appear in crisp detail. Circular convection cells can be seen at high northern and southern latitudes. Atmospheric features as small as 250 miles (400 km) across can be discerned.
More information at Hubble
(Credit: Optical: NASA/ESA/Hubble Heritage (AURA/STScI))

Schematic of Jupiter's Auroral Activity Production
This schematic illustrates how Jupiter's unusually frequent and spectacular auroral activity is produced. Jupiter's strong, rapidly rotating magnetic field (light blue lines) generates strong electric fields in the space around the planet. Particles (white dots) from Jupiter's volcanically active moon, Io, drift outward to create a huge reservoir of electrons and ions. These charged particles, trapped in Jupiter's magnetic field, are continually being accelerated (gold particles) down into the atmosphere above the polar regions, so auroras are almost always active on Jupiter.
(Illustration: NASA/CXC/M.Weiss)