NASA's Galileo spacecraft observed this volcano, Emakong Patera, a large, dark caldera from which numerous bright flows extend out in all directions, on November 25, 1999. Unlike many of the other volcanoes on Io, high-temperature material has never been observed at Emakong. These high-resolution (150 meters, or 164 yards, per picture element) images revealing the intricate nature of the lava flows were taken during Galileo's 25th orbit.

A bright flow emanates to the southeast of the caldera and spreads eastward. A dark channel runs through the flow and may have fed it as it grew. The margins of this bright flow are convoluted, indicating that the lava was able to move through narrow topographic constrictions, or that inexperienced numerous small breakouts. These observations are consistent with a low-viscosity liquid. A contender for the composition of this bright, low-viscosity lava is sulfur. While Galileo has frequently detected high-temperature silicate lava flows, sulfur flows may also be a major component of the surface. Fresh bright flows cover about two-percent of the surface, similar to the coverage by dark flows.

The images were taken at a distance of 15,000 kilometers (9,400 miles) from Io. North is 13 degrees to the left of up. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC. 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.