IoJPL navigation engineer Linda Morabito, double-checking raw Voyager 1 images to ensure that the unmanned space probe is properly aligned for its encounter with Saturn in 1980, discovers the first evidence of active volcanoes on another body in Earth’s solar system: a plume of sulfur erupting over 150 feet above the surface of Jupiter’s moon Io. Scientists rush to check Voyager 1’s other Io images, and find that Voyager’s cameras caught more than half a dozen eruptions in the act.