Data

The Noachis quadrangle is in the ancient cratered highlands of Mars. Craters dominate the surface of the planet in this area; most are of impact origin, some are of volcanic origin, and some are of undetermined origin. Impact craters in the Noachis quadrangle are classified into four groups based on their morphologic characteristics, each group representing a relative age range. Where applicable,

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

The Syrtis Major quadrangle is located in the equatorial belt of Mars across the boundary between the cratered plateau region to the south and west and the northern lowland plains. The cratered plateau is part of the northern extension of cratered highlands, which generally stand at altitudes greater than 4 km. The southeastern part of the quadrangle is dominated by eastward-sloping plains on th

The Arabia quadrangle is located in the northern hemisphere of Mars; it extends 30 degrees N. from the equator and 45 degrees E. from the prime meridian. It is within the area of unmantled terrain defined by Soberblom and others (1973) and the planet-encircling band of old cratered deposits shown on the preliminary geologic map of Mars (Carr and others, 1973). Crater density in the Arabia quadrang

The Iapygia quadrangle, in the equatorial region of Mars just north of the Hellas basin, is mainly ancient, hilly, and cratered upland terrain. The southern one-third of the quadrangle is dominated by mountain and knobby materials representing mountains of pre-Hellas material and material related to the Hellas basin and mappable in a 500-km-wide zone circumjacent to it. The northeast quadrant of t

The Casius quadrangle (30 degrees N to 65 degrees N lat; 240 degrees W to 300 degrees W long) is one of the northern tier of Lambert conformal sheets of the Mars Atlas. It consists of four distinctive physiographic regions: 1) part of the northern cratered plain which forms an incomplete annulus around the north polar region, 2) smooth lowland plains of Utopia Planitia across the central and south

The Amazonis quadrangle lies within the northern sparsely cratered hemisphere of Mars (Carr and others, 1973). The dominant structural and physiographic features of the quadrangle are low featureless plains (Amazonis Planitia) in the center third of the quadrangle, the western flanks of the large volcanic construct, Olympus Mons, and its associated aureole deposits (Lycus Sulci), which lies on the

The Ismenius Lacus quadrangle includes the northernmost extension of the crated highlands that occupy a major part of the southern martian hemisphere. It includes three prominent physiographic provinces: cratered highlands in the south, relatively featureless plains in the middle, and mottled plains in the north. The highlands are separated from the plains by a belt of dissected terrain, containin

The Mare Tyrrhenum quadrangle is bounded by lat 0 degrees and 30 degrees S. and long 225 degrees W. and 270 degrees W. The central part of the quadrangle is dominated by Tyrrhena Patera, a large shield volcano, and associated low-albedo ridged plains that probably are basaltic lava flows similar to the lunar maria. The western, northern, and eastern margins of the quadrangle are located in crater

The Thaumasia quadrangle lies on the south flank of the Tharsis dome (Hord and others, 1974), a large bulge in the crust of Mars extending more than 5,000 km northward from the center of the quadrangle. This major structure imposes a generally southward slope across the entire quadrangle. Topography along the east-central border of the Thaumasia quadrangle exhibits curved scarps and lowlands con

This geologic map of Mars was compiled largely from Mariner-9-based 1:5,000,000-scale geologic maps prepared by several authors. However, many of the geologic units of the larger scale maps have been combined and revised to provide continuity of portrayal so that this map expresses our own concepts as well as those of the mappers at the larger scale.

Two principal physiographic province of Mars are represented in the Aeolis quadrangle: (1) Elysium Planitia in the north is part of a broad planet-encircling belt of relatively young lowland plains, and (2) cratered highlands in the south consist of rough primitive terrain that extends to polar deposits around the southern ice cap (Condit and Soderblom, 1978; Scott and Carr, 1978). These two terr