This mosaic of images shows a portion of a long lava flow that appeared during the 17 years between flybys of Io by NASA's Voyager and Galileo spacecraft. The images are high resolution (35-40 meters, or 38-44 yards per picture element), and were acquired by Galileo on October 11, 1999during its 24th orbit. The lava flow is 100 kilometers (60 miles) long.
The dark flows have intricate margins that are characteristic of a type of lava flow seen on Earth called pahoehoe. The source of the lava flows is a 25-kilometer (16-mile) long fissure that extends to the east of the central vent off the mosaic to the upper left. Some of the lava flows at the western end of the mosaic have channels with bright floors. These channels may have been carved by sulfur lava flows, or they may have been carved by silicate lava flows which were later covered by bright material.
North is to the top of the mosaic. The images were taken at a distance of 3,500 to 4,000 kilometers (2,200 to 2,500 miles) from Io. The large doses of radiation to which the spacecraft is subjected each time it passes close to Jupiter caused a problem with Galileo's camera, which resulted in scrambling of these images. Engineers at NASA's Jet Propulsion Laboratory, Pasadena, CA, were able to reconstruct the images, but black stripes remain where some data could not be recovered. The streaks from lower left to upper right are artifacts from the reconstruction.
JPL manages the mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, CA.
This image and other images and data received from Galileo are posted on the Galileo mission home page at http://solarsystem.nasa.gov/galileo/. Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/gallery/io.cfm.