English: Ganymede, larger than the planet Mercury, is the largest Jovian satellite. Its distinctive surface is characterized by patches of dark and light terrain. Bright frost is visible at the north and south poles. The very bright icy impact crater, Tros, is near the center of the image in a region known as Phrygia Sulcus. The dark area to the northwest of Tros is Perrine Regio; the dark terrain to the south and southeast is Nicholson Regio. Ganymede's surface is characterized by a high degree of crustal deformation. Much of the surface is covered by water ice, with a higher amount of rocky material in the darker areas. This global view was taken in September 1997 when Galileo was 1.68 million kilometers from Ganymede; the finest details that can be discerned are about 67 kilometers across.