[Illustration: As Voyager 1 approached Ganymede on March 5, many strange new surface features became visible. In this frame, taken from a distance of 250 000 kilometers and showing features as small as 5 kilometers across, three distinct types of terrain are seen: polygons of old dark surface, extensive areas of lighter, younger material, and brilliant white ejecta patterns (probably water-ice) around fresh craters. The bright rays in the upper part of the picture are 300-500 kilometers long; at the bottom are several craters with only faint, muted ejecta patterns. [P-21262C]] [Illustration: Voyager 1 found that the surface of Ganymede was geologically very complex. This frame, taken March 5 from a range of 250 000 kilometers, shows a region about 1000 kilometers across centered near longitude 0° and latitude 20°S. The surface displays many craters, some (probably the younger ones) with bright ray systems. Bright grooved bands traverse the surface in various directions. One of these bands, running in a north-south direction in the lower left of the picture, is offset along a white line that may represent a fault. Ganymede is the only Galilean satellite to show indications of such lateral offsets in the crust. [P-21266]] The first picture of Amalthea was shown, revealing an elongated, dark, reddish object about 265 kilometers long. Smith reported: “There is actually some structure that one can see—a crater—a couple of bright features for which we have no interpretation and some other evidence of cratering. It doesn’t look like much, but after all, Amalthea has never been seen as anything more than a point of light from the Earth, and, in fact, there are very few people that have even seen it as a point of light. I doubt that more than one astronomer out of a hundred has actually seen Amalthea.” Larry Soderblom introduced new photographs of the satellites. Io still showed no craters, even at high resolution. The craters that “should” have been on Io were on Ganymede and Callisto. Ganymede not only had craters, it had fault lines as well. “There is transverse motion along these faults. Things get offset, apparently, for hundreds of kilometers. So it’s the first time we’ve seen major kinds of transverse motion on the surface of another planet.” Ganymede, in effect, had shown evidence of having its own icy version of the San Andreas Fault. [Illustration: Amalthea was thought to be the innermost satellite of Jupiter until Voyager 2 discovered tiny Adrastea (1979J1). The Voyager 1 camera revealed Amalthea as an irregular dark reddish object with dimensions of 270 × 160 kilometers. These three images have resolutions of (b) 25 kilometers; (c) 13 kilometers; (d) 8 kilometers. [260-503]] [Illustration: Observation geometry for Amalthea] [Illustration: (b)] [Illustration: (c)] [Illustration: (d)]