This stereo image of Jupiter's moon Io shows the Zal Patera feature and a mountain or plateau that borders it to the west. It was created by combining two different views taken by NASA's Galileo spacecraft on November 25, 1999 (shown in red) and February 22, 2000 (shown in blue). It illustrates the topography of the region. A mountain 120 kilometers (75 miles) wide rises to the west of the patera, a dark volcanic depression. From shadow measurements the eastern margin of this mountain has been determined to be about 1.5 kilometers (5000 feet) high. To the west and northwest, the mountain's margins are scalloped which may indicate that they are being eroded by a process called sapping. Sapping occurs when fluid escapes from the base of a cliff, causing the material above it to collapse. Along the northwestern margin, the rough material at the base of the cliff may be debris left over from the sapping process. Dark lava flows can be seen coming from a fissure to the east of the mountain.

Galileo scientists are in the process of generating topographic maps from these images. Such maps will reveal the heights and slopes of different landforms in this region, which will help scientists to determine the strength and other properties of Io's surface materials. They will also be useful in understanding the processes of uplift and erosion on Io.

The picture is centered at 42.3 degrees north latitude and 76.9 degrees west longitude. North is to the top of the picture. The observations used to make the stereo image were made at ranges of 26,000 and 33,500 kilometers 6,200 and 20,900 miles) from Io. The resolution of the stereo image is about 335 meters (370 yards) per picture element.

Image produced by: Moses Milazzo,

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-02553

May 31, 2000