English: Chasma Boreale (box 1) is about 2 km deep, 580 km long and about 100 km wide. Its walls allow a perfect view into the strata within the deposits. On the canyon floor impact craters are visible, some heavily covered by sand and some partly exhumed. Dark and light-toned deposits (box 2) deposits can be seen in a fine and regular covering. The darker sediments have been dropped by the winds during spring dust storms. The patterns are created when the deposits change in quantity according to the seasons. The northern polar ice cap is surrounded by a large dune field (box 3), parts of which extend 600 km to the south.