Jupiter and Three Galilean Satellites

Jupiter, its Great Red Spot and three of its four largest satellites are visible in this photo taken Feb. 5, 1979, by Voyager 1. The spacecraft was 17.5 million miles (about 28 million kilometers) from the planet at the time. The innermost large satellite, Io, can be seen against Jupiter's disk. Io is distinguished by its bright, brown-yellow surface. To the right of Jupiter is the satellite Europa, also very bright but with fainter surface markings. The darkest satellite, Callisto (still nearly twice as bright as Earth's Moon), is barely visible at the bottom left of the picture. Callisto shows a bright patch in its northern hemisphere. Jupiter's largest moon, Ganymede, is not visible in this image.