Ganymede's Nippur Sulcus region: A Growing Understanding

NOTE: This JPEG image is made available in order to share with the public the excitement of new discoveries being made via the NASA/JPL Galileo spacecraft. Galileo scientists are in the process of calibrating and validating this data. The full digital image necessary for scientific analysis will be released within one year of receipt of this orbit's last data.

This image is available only on the WWW; it is not available in hardcopy or other forms.

This view of the Nippur Sulcus region on Jupiter's moon Ganymede illustrates how our understanding of this boundary between bright and dark terrain is improving as NASA's current Galileo mission builds on the work done by NASA's Voyager missions in 1979. This boundary between bright and dark terrain on Ganymede was observed at a resolution of 1.7 kilometers (1.1 miles) per pixel (picture element) by the Voyager 2 spacecraft in 1979 (left). On September 6, 1996, NASA's Galileo spacecraft flew by at a closer distance, 9728 kilometers (6031 miles) from the surface of Ganymede. The image taken by the Solid State Imaging (CCD) system aboard the Galileo spacecraft has revealed the nature of this boundary at a resolution of 99 meters (325 feet) per pixel (right), a 17-fold increase in resolution. These images measure 27 by 47 kilometers (17 by 29 miles). North is to the top, and the sun illuminates the scene from the southeast. The bright region to the northwest (Philus Sulcus) is composed of parallel sets of fractures, while the dark region to the southeast (Northern Marius Regio) is an ancient terrain dominated by craters and deformed by several episodes of faulting. A bright area crossing the boundary line onto the dark terrain on the right side of the Voyager image was thought to be an area where a flow of bright, volcanically erupted ice had covered the dark surface. In the new Galileo images, the brightening of the surface of this area is seen to be not the result of flows of bright ice, but instead it is the result of intense fracturing of the dark terrain. Two bright spots to the north of this area, interpreted as fresh craters in the Voyager image, are now seen to be chains of fresh secondary craters, formed from debris ejected from a nearby crater.

Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo.

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