This is NASA's Voyager 1 picture of Callisto, the outermost Galilean satellite, taken Feb. 28, 1980. Callisto is the darkest of the Galilean satellites but is still nearly twice as bright as the Earth's Moon.

This Voyager 1 picture of Callisto, the outermost Galilean satellite, was taken February 28 from a distance of about 5 million miles (7 million kilometers). Callisto is the darkest of the Galilean satellites but is still nearly twice as bright as the Earth's Moon. The surface shows a mottled appearance consisting of bright and dark patches. The bright spots remind scientists of rayed or bright haloed craters, similar to those seen on the Earth's Moon. The Galilean satellites all show the same face to Jupiter -- just as the Earth's Moon always shows us the same face. In this photo we see the face of Callisto that always faces Jupiter. JPL manages and controls the Voyager Project for NASA's Office of Space Science.

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