Resurfacing of the Jupiter-facing hemisphere of Io

Four views of the hemisphere of Io which faces Jupiter showing changes seen on June 27th, 1996 by the Galileo spacecraft as compared to views seen by the Voyager spacecraft during the 1979 flybys. Clockwise from upper left is a Voyager 1 high resolution image, a Voyager 1 color image, a Galileo color image, and a Voyager 2 color image. North is to the top of the picture. Voyager and Galileo images have been adjusted to provide comparable color balances similar to Voyager color. The most dramatic changes between Voyagers 1 and 2, just 4 months apart, were the effects of the eruptions of Surt (latitude +45 degrees) and Aten Patera (latitude -48 degrees) which darkened the caldera floors and left diffuse pyroclastic deposits covering areas about 1400 km in diameter (about the size of Alaska). In the Galileo image the Surt and Aten regions appear much more similar to the Voyager 1 pre-eruption images than to the Voyager 2 images. The plume deposits appear to have largely 'faded away' and the calderas have brightened. The Surt and Aten plume deposits had spectral properties similar to the plume deposits of Pele. Pele's deposits have not faded, suggesting that Pele had remained intermittently active whereas Surt and Aten are only rarely active. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at http://www.jpl.nasa.gov/galileo/sepo.