From http://www.jpl.nasa.gov/galileo/

   
                           Galileo Color Image of Io
                                       
   
   
   NOTE: This image is made available in order to share with the public
   the excitement of new discoveries being made via the NASA/JPL Galileo
   spacecraft. Galileo scientists are in the process of calibrating and
   validating this data. The full digital image necessary for scientific
   analysis will be released within one year of receipt of this orbit's
   last data.
   
   This image is available only on the WWW; it is not available in
   hardcopy or other forms.
   
   
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   Shown here is a comparison of a Galileo color image (right) of
   Jupiter's moon Io, with a Voyager mosaic (left) reprojected to the
   same geometry as the Galileo image. The image on the right was
   obtained by the Galileo spacecraft's imaging camera on September 7th,
   1996; the mosaic on the left was obtained by the Voyager spacecraft in
   1979. Color is synthesized from green and violet filters only in both
   cases, as these are the only two filters that are reasonably similar
   between Voyager and Galileo. Many surface changes can be seen due to
   volcanic activity from 1979 to 1996. North is to the top of both
   frames. Galileo was about 487,000 kilometers (302,000 miles) from Io
   on September 7, 1996.
   
   Launched in October 1989, Galileo entered orbit around Jupiter on
   December 7, 1995. The spacecraft's mission is to conduct detailed
   studies of the giant planet, its largest moons and the Jovian magnetic
   environment. 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://www.jpl.nasa.gov/galileo. Background information and
   educational context for the images can be found at URL
   http://www.jpl.nasa.gov/galileo/sepo.