About the image: This view of the Nicholson Regio/Arbela Sulcus region, taken by NASA's Galileo spacecraft, shows the stark contrast between the smooth bright terrain and the surrounding highly fractured dark terrain. Credit: NASA/JPL/Brown University/Doug Ellison
On the Back
Ganymede is the largest moon in our solar system and the only moon with its own magnetic field. The magnetic field causes auroras, which are ribbons of glowing, electrified gas, in regions circling the moon’s north and south poles.
Ganymede has large, bright regions of ridges and grooves that slice across older, darker terrains. These grooved regions are a clue that the moon experienced dramatic upheavals in the distant past. Scientists have also found strong evidence of an underground ocean on Ganymede.
Ganymede is named for a boy who was made cupbearer for the ancient Greek gods by Zeus – Jupiter to the Romans.