Figure 6-58 Martian Terrain This high-altitude photograph shows a variety of the features on Mars, including enormous volcanoes (left) on the highland, called Tharsis Bulge; impact craters (upper right); and vast, windswept plains. The enormous Valles Marineris canyon system crosses horizontally just below the center of the image. Inset: Details of the Valles Marineris, which is about 200 km (120 mi) wide in this image. The canyon floor has two major levels. The northern (upper) canyon floor is 8 km (5 mi) beneath the surrounding plateau, whereas the southern canyon floor is only 5 km (3 mi) below the plateau.