This picture of Io, the innermost Galilean satellite, was taken by Voyager 1 1979 at a range of 377,000 kilometers (226,200 miles). The smallest features visible are about 10 kilometers (6 miles) across. The reddish, white and black areas are surface deposits, consisting of mixtures of salts, sulfur and sublimate deposits of volcanic origin. Many of the black spots in these pictures are associated with craters of possible volcanic origin.
The heart shaped feature in the center of this image was caused by volcanic ejecta thrown out of the eruptive Pele.