ARC-1979-A79-7022

Range : 7 million kilometers (4.3 million miles) Io is Jupiter's innermost of the four Galilean satellites. Photo taken at 2:00 AM through an ultraviolet filter. The photo's background is part of Jupiter's disk. North is at the top and the central longitude of Io is 180 degrees. Io shows a contrasting surface with dark polar areas and many light and dark regions around the equator. This resolution of about 100 miles/160 kilometers, no topographic features, like craters, can be seen. The brighter regions may be areas containing sulfur and various salts, making Io very reflective(six times brighter thanb Earth's Moon). Io is about the same size and density as our Moon, but has followed a different evolutionary path, influenced by its closeness to Jupiter and the intense bombardment it receives from the Jovian radiation belts of energetic charged particles.