PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
 
PHOTO CAPTION                                     P-47058
                                                  July 10, 1996
 
These images demonstrate the dramatic improvement in the
resolution of pictures that NASA's Galileo spacecraft is
returning compared to previous images of the Jupiter system.  The
frame at left was taken by the Voyager 2 spacecraft when it flew
by in 1979, with a resolution of about 1.3 kilometers (0.8 mile)
per pixel.  The frame at right showing the same area was captured
by Galileo during its first flyby of Ganymede on June 27, 1996;
it has a resolution of about 74 meters (243 feet) per pixel, more
than 17 times better than that of the Voyager image.  In the
Voyager frame, line-like bright and dark bands can be seen but
their detailed structure and origin are not clear.  In the
Galileo image, each band is now seen to be composed of many
smaller ridges.  The structure and shape of the ridges permit
scientists to determine their origin and their relation to other
terrains, helping to unravel the complex history of the
planet-sized moon.  In each of these frames, north is to the top,
and the sun illuminates the surface from the lower left nearly
overhead (about 77 degrees above the horizon).  The area shown,
at latitude 10 degrees north, 167 degrees west, is about 35 by 55
kilometers (25 by 34 miles).  The image was taken June 27 when
Galileo was 7,448 kilometers (4.628 miles) away from Ganymede.
The Jet Propulsion Laboratory manages the Galileo mission for
NASA's Office of Space Science.