Data

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

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

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

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

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 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 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

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

The Galindo quadrangle (V-40; centered at lat 12.5 degrees S., long 255 degrees) was geologically mapped at 1:5,000,000 scale under the Venus Data Analysis and Venus Geologic Mapping Programs as part of a project focused on the study of venusian geologic terrains containing assemblages of coronae, arachnoids, and novae; these are enigmatic circular features perhaps related to hot-spot volcanism. M

The Sappho Patera quadrangle (V-20) of Venus is bounded by 0 degrees and 30 degrees East longitude, 0 degrees and 25 degrees North latitude. It is one of 62 quadrangles covering the entire planet at a scale of 1:5,000,000. The quadrangle derives its name from Sappho Patera, a large rimmed depression (diameter about 225 km) lying on top of a shield-shaped mountain named Irnini Mons. Sappho, a noted

The geology of the Argyre quadrangle of Mars is dominated by the conspicuous Argyre basin, defined by a rim of rugged mountain blocks that surrounds a nearly circular expanse of plains 800 km across. Of the large (greater than 500 km in diameter) basins identified on Mars, Argyre is the best preserved and probably the youngest. Basins appear to be traps for eolian debris and evidently are source a

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