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USGS1991

Geologic map of the Valles Marineris region, Mars

The Valles Marineris region lies east of Thar sis Montes (which extend from lat 12 ˚ to 16˚., long 101 ˚ to 125˚). 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 Margar itifer Terra. Channel trends, stereophotogrammetry , and radar altimetery indicate that the surface north and east of the canyons sl o pes toward Chryse Planitia ( centered at about lat 25˚ N., long 45˚). Within the broad Valles Marineris region, three distinct physiographic provinces are recognized (fig. 1): (1) the Noctis Labyrithus province, consisting of a high plateau cut by a network of structurally controlled troughs; (2) the Valles Marineris province, characterized by broad, linear valleys hundreds of thousands of kilometer s long; (3) the eastern canyon province , containing irregular depressions as much as 900 km across. Topography has been determined from a preliminary stereophotogrammetric map having a contour interval and a precision of about 1 km (Wu and others, 1986) and from latitudinal tracks of radar altimetry have a pre cision of 200 m (Roth and others, 1980).

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