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Geology topics

J.F. McCauley

Publications and source records attributed to J.F. McCauley.

25 records · Page 2Linked to original sources
USGS1972

Differentiation and volcanism in the lunar highlands: Photogeologic evidence and Apollo 16 implications

Materials of possible volcanic origin in the lunar highlands include (1) highland plains materials, (2) materials forming closely spaced hills in which summit furrows and chains of craters are common and (3) materials forming closely spaced hills (some of which parallel the lunar grid) on which summit furrows and chain craters are rare. The highland plains materials probably are basaltic lavas with less Fe and Ti than the mare plains materials. The two hilly units appear to consist of materials that, if volcanic, were more viscous in the molten state than any of the lunar plains units; thus these materials may be significantly enriched in felsic components. Most of the highland materials of possible volcanic origin formed after the Imbrium multi-ring basin but before mare material completed flooding parts of the moon; they therefore postdate accretion of the moon and may represent several episodes of premare volcanism.

Earth and Planetary Science Letters↗
USGS1972

The geologic setting of the Luna 16 landing site

The Luna 16 landing site is similar in its geologic setting to Apollos 11 and 12. All three sites are located on basaltic mare fill which occurs mostly within multi-ring basins formed by impact earlier in the moon's history. A regolith developed by impact bombardment is present at each of these sites. The regolith is composed mostly of locally derived volcanic material, but also contains exotic fine fragments that have been ballistically transported into the landing sites by large impact events which formed craters such as Langrenus and Copernicus. These exotic fragments probably consist mostly of earlier reworked multi-ring basin debris and, although not directly traceable to individual sources, they do represent a good statistical sample of the composition of most of the premare terrac regions.

Earth and Planetary Science Letters↗
USGS1972

Mariner 9 television reconnaissance of Mars and its satellites: Preliminary results

At orbit insertion on 14 November 1971 the Martian surface was largely obscured by a dust haze with an extinction optical depth that ranged from near unity in the south polar region to probably greater than 2 over most of the planet. The only features clearly visible were the south polar cap, one dark, spot in Nix Olympica, and three dark spots in the Tharsis region. During the third week the atmosphere began to clear and surface visibility improved, but contrasts remained a fraction of their normal value. Each of the dark spots that apparently protrude through most of the dust-filled atmosphere has a crater or crater complex in its center. The craters are rimless and have featureless floors that, in the crater complexes, are at different levels. The largest crater within the southernmost spot is approximately 100 kilometers wide. The craters apparently were formed by subsidence and resemble terrestrial calderas. The south polar cap has a regular margin, suggesting very flat topography. Two craters outside the cap have frost on their floors; an apparent crater rim within the cap is frost free, indicating preferential loss of frost from elevated ground. If this is so then the curvilinear streaks, which were frost covered in 1969 and are now clear of frost, may be low-relief ridges. Closeup pictures of Phobos and Deimos show that Phobos is about 25 ±5 by 21 ±1 kilometers and Deimos is about 13.5 ± 2 by 12.0 ±0.5 kilometers. Both have irregular shapes and are highly cratered, with some craters showing raised rims. The satellites are dark objects with geometric albedos of 0.05.

Science↗
USGS1971

Geological provinces of the near side of the moon

Systematic geologic mapping of the near side of the Moon has provided the basis for defining and delineating the major geological provinces of the near side. From the nature of the provinces and their distribution patterns a general historical sequence evolves. Five main surface-shaping periods are recognized: (1) one of intense early impact cratering; (2) another, probably overlapping the first, during which the impact basins were formed; (3) a prolonged period of varied terra volcanism; (4) a short period of mare volcanism that resulted in filling of the multiring basins; and (5) a period of diminishing volcanic activity continuing up to the time of formation of the last ray craters.

Icarus↗
USGS1969

(RLC-15) Geologic map of the Alphonsus GA region of the moon

This ma p is one of a series prepared from photographs transmitted by R anger IX (Jet Propulsion L ab ., 1966. , pls. A56-A58, B70-B82). It depicts the geology of some 724 sq km in the northeast p a rt of the floor of Alphon s us (diameter about 115 km), a typical flat-floored old terra crater or basin with subdued rim. Similar basins abound in the south-central tarrae of the visible hemisphere and on the far side of the Moon. Alphonsus is of particular inte re st, however, because of a well-developed interior rille system and a ssociated dark-halo craters.

IMAP↗