The prediction was made by Stanton J. Peale who wrote a scientific paper claiming that Io must be volcanically active that was published one week before Voyager 1 encountered Jupiter. When Voyager 1 photographed Io in 1979, his theory was confirmed.[1] Later photographs of Io by the Hubble Space Telescope and from the ground also showed volcanoes on Io's surface, and they were extensively studied and photographed by the Galileo orbiter of Jupiter from 1995-2003.