Chasma Boreale (2)

Tapering from a width of 120 Km (75 miles) at its mouth, Chasma Boreale is only about 35 Km (22 miles) wide here. The cliffs on the Northern (top) and Eastern (right) sides of the image rise about 1400 meters (4600 feet) above the base. On the inside walls of this gigantic amphitheater are stacked layers of ice, while on its floor lie a dark sheet of what is likely frozen sand and a horde of sand dunes marching down-canyon under the winds' direction.
Chasma Boreale is so dramatic a feature that it forms part of a proposed martian "Polar Park." Yet setting aside future tourist revenues, the canyon is rewarding scientists today with glimpses into the history of the martian climate.