Changes in the volcanoes on Jupiter's moon Io can be seen in these three views, taken by NASA's Galileo spacecraft during its three flybys of Io in October 1999, November 1999 and February 2000.
All the images show the active volcanoes as bright yellow, corresponding to hot lava flows that appear glowing in infrared wavelengths. The three views were taken by the spacecraft's near-infrared mapping spectrometer instrument and show the comparison of a typical low-resolution observation to the high-resolution views. The regional observations taken during the recent Io flybys are superimposed on an image taken during Galileo in 1996.
The Prometheus volcano is seen near the middle of all three images. Before the recent flybys, only Prometheus and three other volcanoes were known to be active in this region. After these and other high-resolution observations, scientists were able to detect 14 volcanoes in the same area. The fainter volcanoes (hot spots) show some significant changes over intervals of 1 to 3 months. The area shown by all three observations put together is about 2 million square kilometers (about 770,000 square miles) and covers about 5 percent of Io's surface.
The Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.
This image and other images and data received from Galileo are posted on the World Wide Web, 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://solarsystem.nasa.gov/galileo/gallery/index.cfm.