This image shows one of many intriguing mountains on Jupiter's moon Io. The image was made by combining a recent, high-resolution, black and white image with earlier low resolution color data to provide a high resolution, color view. Both images were taken by NASA's Galileo spacecraft.
The 240 kilometer (150 mile) long mountain in the image is south of the volcanic hot spot named Zal. The black and white version of this image was useful for showing the shape of the mountain and the small fans of debris piled against the base of its tall, steep, cliffs. However, when colorized, the relationship between different types of materials becomes apparent. For example, the bright, red material is believed to contain a compound of sulfur that forms when sulfur is boiled at a high temperature. Active eruptions of lten rock (lava) are the most likely source for the heat. Thus we see red sulfur where lava reaches the surface. The yellow areas are covered by other sulfur compounds and the black areas are fresh silicate lava that has not yet been coated by the yellow sulfurous materials. The green patches are still somewhat mysterious; they appear to form when red sulfur lands on warm lava and the two react in a manner that is still unknown.
In this image, it is clear that the red material has blown out of a long crack along the western side of the mountain. Lava has flowed from this crack and filled a caldera (volcanic depression). Some of the red sulfur close to the dark caldera appears to have been converted into green material. The fact that lava comes up along the faults that define the sides of the mountains provides important clues to how the mountains form and the state of the interior of Io. Scientists at the University of Arizona speculate that the formation of the mountains on Io may be related to plumes of hot material rising inside the fiery body of Io.
North is to the top and the setting sun is shining from the west. The image is centered at 33.4 north, 72.4 west. The high resolution image was taken on February 22, 2000 by NASA's Galileo spacecraft during its 27th orbit around Jupiter. The image was taken by the Galileo's onboard camera from a range of 33,500 kilometers (20,800 miles) and has a resolution of 335 meters (1100 feet) per picture element. The color images were taken on July 3, 1999. They have resolutions of 1.3 kilometers (0.81 miles) per picture element and are illuminated from almost directly behind the spacecraft. They were taken at a distance of about 130,000 kilometers (81,000 miles) from Io.
Image produced by: Moses Milazzo, Planetary Image Research Lab. (PIRL), Lunar and Planetary Lab. (LPL), University of Arizona
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo 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 World Wide Web, on the Galileo mission home page at http://galileo.jpl.nasa.gov/. Background information and educational context for the images can be found at http://galileo.jpl.nasa.gov/images/io/ioimages.html.
NASA's Planetary Photojournal PIA-02554
May 31, 2000