June 19, 1997: The Hubble telescope has snapped a picture of a 400-kilometer-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large, innermost moon.
Io was passing in front of Jupiter when Hubble took this image. The plume appears as an orange patch just off the edge of Io [at eight o'clock], against the blue background of Jupiter's clouds. Io's volcanic eruptions blast material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.
Credit: John Spencer (Lowell Observatory) and NASA