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At least 739 records · Page 41Linked to original sources
USGS1986

Geologic map of the western equatorial region of Mars

The r egional topographic swell centered in the Tharsis Montes and Syria Planum extends over one-third of the map area (U.S. Geological Survey, 1976). Within this high region are the four largest and youngest volcanoes on Mars: Olympus Mons, Arsia Mons, Pavonis Mons, and Ascrae us Mons. The latter three collectively form the large northeast-trending, volcanic mountain chain of the Tharsis Montes. This volcanic chain lies athwart the global highland - lowland boundary that transects the western equatorial region. The boundary, where not covered b young lava flow s, is marked by a gentle, irregular scarp bordered by clusters of low knobby hills. It separates the relatively smooth, flat, spar sely cratered northern plains from the higher, rougher, more densely cratered plateau terrain of the southern highlands . A vast system of canyons, the Valles Marineris , originates in Noctis Labyrinthus , just east of the Tharsis -Sy ria swell, and extends eastward for several thousand kilo meters. Ancient rivers channels appear to have sources in canyons and chaotic terrain north of Valles Ma rineris and in a large fissure at the head of the Mangala V alles. Visible remnants of large circular basins are not as common on Mars as on the Moon, probably because of more active erosion and deeper burial on Mars by eolian and fluvial activity and by widespread volcanism on both the highlands and plains. The youngest and b est preserved impact basin on Mars, lying in the western hemisphere , is more than 1,00 0 km across. It has a broad flat floor ( Argyre Planitia) covered by eolian materials and volcanic flows ; the floor is several kilometers below its encompassing rough mountainous rim.

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USGS1987

Geologic map of the eastern equatorial region of Mars

The M ariner 9 mission in the early 1970’s provided the first comprehensive view of the geology of Mars (McCauley and others, 1972, Masursky , 1973) and led to the derivation of the first global geologic map ( Carr and others, 19 73). These preliminary studies were followed by more comprehensive mapping coordinated with the U.S. Geological Survey. Thirty quadrangles at a scale of 1:5 , 0 00,000 were produced in this map series, from which Scott and Carr (1978) compiled a single geologic map at a scale of 1:25,000,000. The reliability of these maps, however, is varied because of the uneven quality of the Mariner 9 data.

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USGS1987

Geologic map of the polar regions of Mars

These geologic maps of the north and south polar regions of Mars, extend ing to 55 ˚ north and south latitudes, overlap by 2 ˚ the geologic maps of the western and eastern regions, which extend to lat ± 57 ˚ . The maps were compiled from Viking medium-resolution photomosaics at scales of 1:2,000,000 and from higher resolution Viking images. The quality and resolution of the Viking pictures are superior to those of Mariner 9 used to prepare the previous maps (Scott and Carr , 1978) that includes these two regions. Because of the Viking orbital configuration, a vast number of high-resolution images of the area within 10 ˚ of the north pole was obtained, whereas many areas in lower northern latitudes were covered only by low-resolution images. In contrast, the south polar region is nearly completely covered by images at medium resolution but is not image d at high resolution.

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