3/4/79 2.6 million km (1.6 million mi)
Ganymede, Jupiter’s largest satellite, is about one and one-half times the size of our Moon but only about half as dense and is composed of about 50 percent water or ice and the rest rock. The bright surface of Ganymede is a complex montage of ancient, relatively dark and cratered terrain, grooved terrain that resulted from a dramatic history of tectonic movement in the icy crust, and bright young ray craters that expose fresh ice. This photograph was taken by Voyager 1.
7/7/79 1.2 million km (750,000 mi)
The dark, cratered, circular feature in this Voyager 2 photograph is about 3200 kilometers (2000 miles) in diameter and is on the side of Ganymede opposite to that shown in the previous picture. This region is apparently the largest piece of ancient, heavily cratered crust left on Ganymede. The light branching bands are ridged and grooved terrain which are younger than the more heavily cratered dark regions. Despite the dramatic surface appearance, Ganymede is relatively devoid of topographic relief due to the consequences of glacier-like “creep” in the icy crust.
7/8/79 312,000 km (194,000 mi)
Several different types of terrain common to Ganymede’s surface are visible in this Voyager 2 picture. The boundary of the largest region of dark ancient terrain (also shown in the previous photo) can be seen to the right, revealing the light linear features that may be the remains of shock rings from an ancient impact. The broad light regions are the typical grooved structures contained within the light regions on Ganymede. On the lower left is another example of what might be evidence of large-scale lateral faulting in the crust; the band appears to be offset by a linear feature perpendicular to it. These are the first clear examples of lateral faulting seen on any planet other than Earth.
7/8/79 313,000 km (194,500 mi)