Io: The Prometheus Plume . ... Credit Copyright: Galileo Project , JPL , NASA Explanation: Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite Galileo image . ... In the middle of the image, near the night/day shadow line, the ring shaped Prometheus plume is seen rising 45 miles above Io while casting a shadow to the right of the volcanic vent. ... This image was recorded on June 28 at a distance of 372,000 miles. ... NASA Official: Jay Norris. ...