Four views of the volcano Ra Patera on Jupiter's moon Io 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.
Observations obtained by J. Spencer and others with the Hubble Space Telescope had indicated a major change in recent years. The Galileo images reveal the detailed morphology of new deposits. Dark materials, previously confined to a summit caldera, appear to have overflowed the caldera walls to produce a small flow to the south and a larger flow to the southeast. New bright deposits covering an area of about 40,000 square kilometers (the size of New Jersey) surround the dark materials.
The morphology of the bright materials suggests emplacement as lava flows rather than pyroclastics. Notice the lobate margins and how the bright materials embay a plateau in the upper left. The Voyager 1 images also reveal relatively bright lava flows emanating from Ra Patera, especially to the northeast. The colors of the flows match those of sulfur plus SO2 frost. Images are 953 km wide.
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 URL http://www.jpl.nasa.gov/galileo/sepo. Image Credit: NASA/JPL