Changes on the Surface of Io

This Hubble Space Telescope pair of images of Jupiter's volcanic moon Io shows the surprising emergence of a 200-mile diameter large yellowish-white feature near the center of the moon's disk (photo on the right). This is a more dramatic change in 16 months than any seen over the previous 15 years, say researchers.

For comparison the photo on the left was taken in March 1994 -- before the spot emerged -- and shows that Io's surface had undergone only subtle changes since it was last seen close-up by the Voyager 2 probe in 1979.