HELLAS BASIN

Mosaic of the Martian surface. Hellas basin is the light region in the lower right. Its brightness 1/4 Hellas region of Mars, showing the planet's varied terrain. The eastern portion of the Hellas basin 1/4 largest recognizable impact feature on the planet Mars, measuring about 2,000 km (1,250 miles) in diameter. Photographs taken by the U.S. Viking spacecraft (landed 1976) revealed that the basin's floor, which was once erroneously thought to be featureless, is the lowest topographic region on Mars, lying some 4 km (2.5 miles) below the planet's mean surface level.