Ganymede (Enhanced Natural Colors and HR; credits: NASA/JPL)

Caption NASA originale:"This color reconstruction of part of the Northern Hemisphere of Ganymede was made from pictures taken from a range of about 313.000 Km (approx. 194.000 miles).
The scene is approx. 1.300 Km (about 806 miles) across and it shows part of dark, densely cratered block which is bound on the south by lighter and less cratered, grooved terrain.
The dark blocks are believed to be the oldest parts of Ganymede's surface. Numerous craters are visible, many with central peaks. The large bright circular features have little relief and are probably the remnants of old, large craters that have been annealed by flow of the icy near-surface material.
The closely-spaced arcuate, linear features are probably analogous to similar features on Ganymede which surround a large impact basin.
The linear features here may indicate the former presence of a large impact basin to the South-West".