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

   
 Changes on Io between Voyager 1 and Galileo's second orbit around an unnamed
                           vent North of Prometheus
                                       
   
   
   NOTE: This JPEG 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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Changes on Io between Voyager 1 and Galileo's second orbit around an unnamed
vent North of Prometheus

   
   
   Detail of changes around a probable vent about 650 kilometers north of
   Prometheus on Jupiter's moon Io as seen in images obtained by the
   Voyager 1 spacecraft in April 1979 (left) and the imaging system
   aboard NASA's Galileo spacecraft on September 7th, 1996 (right). The
   re-arranging of dark and light radial surface patterns may be a result
   of plume fallout. North is to the top of both images which are
   approximately 400 kilometers square.
   
   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.