Geology topics

Research about Mars

Source-linked reports with geographic coverage including Mars.

At least 325 records · Page 18Linked to original sources

USGS1994

Geologic map of science study area 4, Chasma Boreale Region of Mars

This map is one is a series of 1:500,000 scale maps initiated by the National Aeronautics and Space Administration to investigate Science Study Areas (selected area of scientific interest) on Mars (fig. 1). The Chasma Boreale region merits detailed geologic study because it contains parts of (1) the north polar ice cap, which is composed of water ice with lesser amounts of carbon dioxide; (2) the layered terrain that recorded climatic and atmospheric changes on Mars during the Amazonian Period; and (3) the enigmatic low-lying polygonal patterned terrain. The map was compiled on a composite of three 1:500,000-scale photomosaic bases (U.S. Geological Survey, 1986a, b, c), each of which is the summer scene of a two-sheet set that includes a spring scene. (Summer scenes, acquired when the north polar ice cap is smallest, show the greatest extent of underlying materials. However, spring scenes that show more detail in specific areas were also used.) Map units (including crater materials) and contacts are generally consistent with those of Howard and others (1982), Dial (1984), and Tanaka and Scott (1987) except where revised on the basis of higher resolution Viking images. Several Viking images were computer enhanced for our mapping.

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USGS1994

Geologic map of the MTM -85080 quadrangle (revised), Planum Australe region of Mars

Published geologic maps of south polar region of Mars have been based on either Mariner 9 (Condit Soderblom, 1978; Scott and Carr, 1978) or Viking Orbiter (Tanaka and Scott, 1987) images. The mapped extent of the southern layered deposits differs in many places on these maps and on our maps. These differences reflect the difficulty in accurately determining the location of the contact between the layered deposits and subjacent units. The polar layered deposit gradually thin toward their margin in many places, and the smooth surface features that characterize the layered deposits are also found on other sedimentary blankets in the south polar region (Murray and others, 1972; Sharp, 1973). Previous workers have also reached different conclusions regarding the origin of the lower member of the Dorsa Argentea Formation, which was named by Tanaka and Scott (1987) and interpreted by them as volcanic in origin (based on observation of flow fronts in areas far outside this quadrangle). The lower member, previously called pitted material, and other sedimentary, and other sedimentary units were recognized in Mariner 9 images and described by Murray and others (1972), Sharp (1973), and Cutts (1973b). Sharp (1973) argued for exhumation of pits by wind, perhaps aided by sublimation of volatiles. He concluded that the massive pitted sediments of the lower member unconformably overlie older massive units. We have mapped one of these older units ridged and knobby material. Condit and Soderblom (1978) found some layered deposits within pits, which indicates that erosion of the pits was completed before accumulation of the layered deposits commenced. Howard’s (1981) suggestion that the pits may be formed by basal melting of ground ice is consistent with either a volcanic or sedimentary origin for the lower (pitted) member. Plaut and others (1988) mapped the extent of the pitted material and found that it overlies volcanic plains wherever the contact is visible. They concluded that the pitted material is no more than 1 km thick and is about 3.3 billion years old (Late Hesperian).

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USGS1993