Compositional Variations in Callisto's Asgard Impact Structure

These frames combine data from two of the instruments aboard NASA's Galileo spacecraft. The left image is from the Solid State Imaging (SSI) system and the right frame shows data from the Near Infrared Mapping Spectrometer (NIMS) overlaid on the SSI data. North is to the top of the images. The area to the northeast (upper right corner) of the NIMS observation shows the southwest part of the ancient impact structure Asgard on Jupiter's moon Callisto. The Asgard multi-ring system has a central bright zone approximately 230 km (140 miles) across, surrounded by concentric rings out to 800 km (480 miles). The rings are fractured parts of the surface with scarps near the central zone and troughs at the outer margin. Impact craters ranging in size down to the limit of resolution are visible throughout the image.

The NIMS observation of a small section of the Asgard terrain reveals compositional variations over the surface of Callisto. Red indicates a high concentration of clean ice at the floor of an impact crater while blue shows large amounts of non-ice material on the surrounding surface.

The data in these images were taken on November 4, 1996, at a distance of 111,891 kilometers (69,900 miles) by the Solid State Imaging (CCD) system and 17,920 kilometers (11,200 miles) by the Near Infrared Mapping Spectrometer aboard NASA's Galileo spacecraft during its third orbit around Jupiter. The area seen in the SSI image is 440 kilometers by 440 kilometers across at 1.1 kilometers per picture element (pixel) resolution, centered near 17 North, 153 West, while the resolution for the NIMS observation is 8 kilometers per pixel.

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/sepo.