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.

Last modified September 4, 2001 by Jennifer Bergman.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more


The Galileo spacecraft was launched on October 19, 1989. Galileo had two parts: an orbiter and a descent probe that parachuted into Jupiter's atmosphere. Galileo's main mission was to explore Jupiter and...more


Callisto was first discovered by Galileo in 1610, making it one of the Galilean Satellites. Of the 60 moons it is the 8th closest to Jupiter, with a standoff distance of 1,070,000 km. It is the 2nd largest...more

Galilean Satellites

The Galilean satellites are the 4 major moons of Jupiter, Io, Europa, Ganymede, and Callisto. In this picture, Io, and Ios surface, are shown on the left-most end, then Europa, and its surface, then Ganymede,...more

1999--A Year in Review...

It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more

STS-95 Launch: "Let the wings of Discovery lift us on to the future."

The Space Shuttle Discovery lifted off from Kennedy Space Center on October 29th at 2:19 p.m. EST. The weather was great as Discovery took 8 1/2 minutes to reach orbit. This was the United States' 123rd...more

Moon Found Orbiting Asteroid

A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more

U.S. is Fed Up with Russia

Will Russia ever put the service module for the International Space Station in space? NASA officials want an answer from the Russian government. The necessary service module is currently waiting to be...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA