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C. A. Hodges

Publications and source records attributed to C. A. Hodges.

10 recordsLinked to original sources
USGS1980

Geologic map of the Argyre quadrangle of Mars

The geology of the Argyre quadrangle of Mars is dominated by the conspicuous Argyre basin, defined by a rim of rugged mountain blocks that surround 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 possibly youngest. Basins appear to be traps for eolian debris and evidently are source areas for some of the dust storms that periodically envelop the planet. The quadrangle lies within the densely cratered province that characterizes the southern hemisphere, contrasting with sparsely cratered plains generally confined to the northern hemisphere. Northwest of Argyre an outlier of sparsely cratered, ridged plains extends into the quadrangle from the Coprates region. Northeast of the basin are the cratered uplands, parts of which are presumed to represent remnants of the earliest martian crust (Wilhelms, 1974). South of the quadrangle the cratered plateau is replaced by the pitted, etched, layered, and mantled terrains that characterize the south polar region (Sharp, 1973a; Condit and Soderblom, 1978). Constructional volcanic landforms were not recognized within the map area.

IMAP↗
USGS1978

Formation of lunar basin rings

The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing “megaterrace” hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins—the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris—define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon—the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying, more coherent “heald” crust, and an innermost, 320-km ring at the crust-mantle interface. Depth-diameter ratios of 1 10 to 1 15 "> 110 to 115 are consistent with this interpretation and suggest that volumes of transient cavities and hence of basin ejecta may be considerably greater than commonly assumed.

Icarus↗
USGS1977

The Aristarchus-Harbinger region of the moon: Surface geology and history from recent remote-sensing observations

The region including the Aristarchus Plateau and Montes Harbinger is probably the most diverse, geologically, of any area of comparble size on the Moon. This part of the northwest quadrant of the lunar near side includes unique dark mantling material; both the densest concentration and the largest of the sinuous rilles; apparent volcanic vents, sinks, and domes; mare materials of various ages and colors; one of the freshest large craters (Aristarchus) with ejecta having unique colors and albedos; and three other large craters in different states of flooding and degradation (krieger, Herodotus, and Prinz). The three best-authenticated lunar transient phenomena were also observed here. This study is based principally on photographic and remote sensing observations made from Earth and Apollo orbiting space craft. Results include (1) delineation of geologic map units and their stratigraphic relationships; (2) discussion of the complex interrelationships between materials of volcanic and impact origin, including the effects of excavation, redistribution and mixing of previously deposited materials by younger impact craters; (3) deduction of physical and chemical properties of certain of the geologic units, based on both the remote-sensing information and on extrapolation of Apollo data to this area; and (4) development of a detailed geologic history of the region, outlining the probable sequence of events that resulted in its present appearance. A primary concern of the investigation has been anomalous red dark mantle on the Plateau. Based on an integration of Earth- and lunar orbit-based data, this layer seems to consist of fine-grained, block-free material containing a relatively large fraction of orange glass. It is probably of pyroclastic origin, laid down at some time during the Imbrian period of mare flooding. ?? 1977 D. Reidel Publishing Company.

The Moon↗
USGS1973

Geologic map of the Langrenus Quadrangle of the Moon

The Langrenus quadrangle is on the east limb of the lunar nearside, at the southeast margin of Mare Fecunditatis . The crater Lan grenus , about 140 km in diameter, is the most prominent feature. Rugged terra materials, scattered by craters of various sizes and ages, occupy much of the east half of the map area, and smooth mare materials in the Fecunditatis basin dominate the west. Mare Spumans and other irregular maria in the northeast are part of a belt of such maria concentric with Mare Crisium , which is centered approximately 500 km north of the quadrangle.

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USGS1973

Geologic map of the Petavius quadrangle of the Moon

The large crater Petavius , about 180 km in diameter, is the dominant geologic feature within this quadrangle at the southeast border of Mare Fecunditatis on the east limb of the near side. Four categories of materials have been distinguished herein : (1) terrae, with r u gged to gently rolling topography and moderate albedo; (2) plains, of low relief and moderate albedo; (3) craters, with low to rugged relief and low to high albedo; (4) maria, with essentially no reli e f and very low to moderately low albedo. Materials are places in chronologic sequence according to stratigraphic position and(or) physical characteristics believed indicative of relative age. Development of the lunar time-stratigraphic nomenclature has been summarized by Wilhelms (1970).

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USGS1972

Geologic maps of the Descartes region of the Moon Apollo 16 pre-mission maps

The evolution of the Moon’s s urface shows three successive stages (Hartmann, 1970). The earliest , from the beginning of the decipherable record to the Imbrian P eriod, was dominated by frequent large -scale impacts which produced overlapping and interfering craters and g iant multi-ringed basin with ejecta blankets. The second stage , extending through most of the Imbrian to early Eratosthenian Periods , was characterized by volcanism, producing basalt flows of the maria an vari ed materials on the terrae . The final and longest stage , extending through the greater part of the Eratosthe n ian Period and the whole of the Copernican , was one of reduced geologic activity. Major modifications of the geologic structure by large impacts of volcanism occurring only locally, although changes by small-scale impact and mass wasting affected the entire surface. The De s cartes region, in the central highlands of the Moon about 500 km southeast of the center of the lunar disk, is dominated by features of the middle st a ge and contains a n exceptionally favorable site for their study.

IMAP↗
USGS1972

Preliminary geologic investigation of the Apollo 16 landing site

The Apollo 16 landing site in the lunar central highlands encompassed terra plains and adjacent mountainous areas of hilly and furrowed terra. These morphologic units, representing important terrane types in the lunar highlands, had been interpreted as volcanic on most premission geologic maps. However, it became apparent during the mission that there are indeed few or no volcanic rocks or landforms at the site but rather that the area is underlain by a wide variety of impact-generated breccias.

Book chapter↗