Data

The map area, in the Coprates 1:2,000,000-scale quadrangle MC-18 NW lies in the heart of the Valles Marineris trough system. The western part of Ophir Planum (36,660 km2) occupies 40 percent of the map areas; parts of Candor, Melas, and Coprates Chasmata make up the remainder. The troughs contain distinctive landslide deposits, normal faults, possible young volcanic rocks, and layered materials.

The application of stratigraphic and structural principles to geologic mapping of the Moon from telescopic photographs has been discussed by Shoemaker (1962) and Shoemaker and Hackman (1962). Major geologic units are recognized by regional topographic and albedo differences. Pictures returned by Ranger, Surveyor, and Lunar Orbiter spacecraft show that a fragmental regolith, presumably produced by

Material exposed on the surface of the moon is heterogeneous. The albedo and other physical characteristics that have been determined with the use of optical and radio telescopes vary from one part of the moon to another, and the variations are patially correlated with differences in topography . Discontinuities in the areal variation permit the surfaces material to be divided into map units, each

Material exposed on the surface of the moon is heterogeneous. The albedo and other physical characteristics that have been determined with the use of optical and radio telescopes vary from one part of the moon to another, and the variations are partially correlated with differences in topography . Discontinuities in the areal variation permit the surfaces material to be divided into map units, eac

The Tharsis quadrangle lies within the sparsely cratered hemisphere (Carr and others, 1973) of Mars. Its geology is dominated by young volcanic features, including both circular constructs and lava plains; little evidence of primitive densely cratered terrain remains. Included are three of the four largest shield volcanoes in the Tharsis province, Olympus Mons, Ascraeus Mons, and Pavonis Mons, t

Mars presents two different terrains, a highly cratered surface that lies mostly in the southern hemisphere and sparsely cratered plains that lie mostly in the northern hemisphere. The cause of the dichotomy is a still unsolved fundamental problem of Martian geology, analogous to the problem of continents and ocean basins in terrestrial geology. The present features of the plains in particular r

The Oxia Palus quadrangle contains three distinct geologic provinces: (1) an elevated cratered plateau that occupies three-fourths of the quadrangle and is similar to much of the southern hemisphere of Mars; (2) the low, relatively featureless Chryse Planitia in the northwest corner; and (3) a complex province of chaotic terrain and immense channels or valleys that divides the plateau an determina

The Coprates quadrangle lies to the east of the Tharsis volcanic complex and the Noctis Labyrinthus tectonic complex. To the north are the plains of Lunae Planum, to the east the vast patches of chaotic terrain and the large sinuous channels that trend northward into Chryse Planitia. On the southwest is the Thaumasia Fossae region of tectonically deformed cratered terrain, to the southeast, the A

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 Grimaldi quadrangle lies at the southwest margin of Oceanus Procellarum about 1,000 km east of Orientale, the youngest of the lunar multi-ringed basins. The distal ends of the ejecta blanket surrounding the Orientale basin partly covers the western third of the quadrangle. The relatively small, two-ring Grimaldi basin is in the northwest corner of the quadrangle, and the Humorum basin lies abo

The Valles Marineris region lies east of Tharsis Montes (which extend from lat 12 degrees to 16 degrees., long 101 degrees to 125 degrees). Part of the region is in the midst of a vast plateau bounded on the west and east by Claritas and Nectaris Fossae, respectively; the remainder extends farther east into southern Xanthe Terr and western Margaritifer Terra. Channel trends, stereophotogrammetry,

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the venusian atmosphere on October 12, 1994. Magellan had the objectives of (1) improving knowledge of the geologic processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving knowledge of the geophysics of Venus by analysis o