This picture of Callisto was taken by Voyager 2 from a distance of 2,318,000 kilometers (1,438,000 miles).

This close-up picture of Callisto was taken by Voyager 1 Tuesday, March 6, during its approach to Jupiter's outer large satellite

This picture of ganymede was taken on March 4, 1979 at 2:30 A.M. PST by Voyager 1 from a distance of 2.6 million kilometers (1.6 million miles).

This picture of Europa, the smallest Galilean satellite, was taken on March 4, 1979, from a distance of about 2 million kilometers (1.2 million miles) by Voyager 1.

This color image of the Jovian moon Europa was acquired by Voyager 2 during its close encounter on Monday morning, July 9

This view of Io was taken on March 4 at 7:00 PM from a range of 862,200 kilometers (500,000 miles) by Voyager 1.

This picture of Io, the innermost Galilean satellite, was taken by Voyager 1 on the morning of March 5, 1979 at a range of 377,000 kilometers (226,200 miles).

This NASA Hubble Space Telescope pair of images of  Io shows the surprising emergence of a 200-mile diameter largey ellowish-white feature near the center of the moon's disk (photo on the right).

Jupiter's innermost satellite, Amalthea orbits around the planet every 12 hours, only 1.55 Jupiter radii from the cloudtops.