An infrared thermal map and a visible-light image from NASA's Galileo spacecraft show the likelihood of an active lava lake at a volcanic feature called Gish Bar on Jupiter's moon Io.
Galileo observed the Gish Bar region with the spacecraft's near-infrared mapping spectrometer instrument in August 2001 (right) and with its solid-state imaging camera in October 2001 (left). Comparison of the camera image with the infrared thermal map and with earlier images, (see PIA03884) suggests that a new eruption took place shortly before the October 2001 flyby. The darkest areas in the visible-light image are interpreted as the youngest lava flows, but they do not correspond with the hottest areas in the infrared thermal map from two months earlier. Outlines of the areas that were identified as hotter than 350 degrees Kelvin (170 degrees Fahrenheit) in the thermal map are superimposed on the visible-light image. North is toward the top. The dark flow on the western side of the crater in October corresponds to a cool area in the earlier thermal map, indicating that the flow took place between the time Galileo flew by in August and the time it flew by in October.
The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. Additional information about Galileo and its discoveries is available 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.