These views of Callisto were taken in May 2001 by the Galileo spacecraft. The top insert shows the sharp, knobby terrain experiencing erosion. As they stand now, the knobs are about 80 to 100 meters (260 to 330 feet) tall. As these knobs erode and disappear, the terrain will look more and more like the bottom insert. The smallest features discernable in these images are about 3 meters (10 feet) across.
Click on image for full size
Courtesy of NASA/JPL/Arizona State University
A Revealing Look at Callisto
News story originally written on September 5, 2001
The Galileo spacecraft
was only 86 miles (138 km) above the surface of Callisto when it took the pictures to the left. These are the highest resolution views ever seen of any of Jupiter's moons
. You can see features in these pictures that are just 10 feet (3 m) across!
Scientists were surprised when they saw the top insert picture. The knobby hills appear to have dark dust slumping off of the peaks of the hills, signifying erosion. But scientists thought Callisto was geologically dead! Scientists aren't exactly sure how these hills were originally formed or why they are experiencing erosion. They do know that if the erosion continues, the hills will eventually disappear. The lower insert picture shows a part of the surface where some of the hills have eroded away, leaving behind flat plains of dark material where knobby hills used to stand.
Callisto is one of the Jupiter's Galilean moons. Callisto is an icy moon about the same size as Mercury.
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