Geologic map of the Hellas Quadrangle of Mars

The area of MC-28 is centered at the east edge of the Hellas Planitia (Hellas basin and surrounding plains) within densely cratered terrain that covers more than half the surface of Mars (Carr, 1973). The deepest part of the basin lies 4-5 km below the surface of the cratered terrain (Hanel and others, 1972). An irregular band of mountain and knobby material about the eastern margin of the basin and broad bands of mantled rough material on the floor of the basin represent ejecta from this very old impact. The vast, gently sloping, featureless eastern and southern part of Hellas Planitia, shown on the Shaded Relief Map of Mars (U.S.G.S., Atlas of Mars, MM 25M IR, 1972), is probably the result of extensive volcanic flooding form shield volcanoes and from possible fissures in the north-east part of the quadrangle. Long, flat-floored sinuous channels originate in these volcanic terrains and course into the basin.