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Mckay, D. S.

Publications and source records attributed to Mckay, D. S..

108 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Iron crystals in lunar breccias

Many of the vugs in the highly recrystallized breccias from Apollos 14, 15, and 16 contain euhedral iron crystals. Three populations have been recognized based on crystal habit. In the first group the trapezohedron predominates and the cube faces are smaller. The second group is characterized by the cube as the dominant form; trapezohedron and tetrahexahedron faces are smaller and about equally developed. The dominant habit of the third group is the octahedron with smaller but equally developed cube and dodecahedron faces. Iron has been mobilized and redistributed in a vapor phase. The euhedral crystals, the abundant growth steps, and the open network of substrate crystals clearly support the concept of growth from a vapor-phase.

Clanton, U. S.↗
NASA NTRS1973

Microcraters on Apollo 15 and 16 rocks

Microcrater frequency distributions, determined for 11 Apollo 16 rocks and three Apollo 15 rocks, fall into four categories. Category 1 rocks (68415, 68416, 62235) are angular, cratered on one side only, and have moderate crater densities. Category 2 rocks (60016, 66075, 61175) are subrounded, cratered on all sides, and have distributions suggestive of the steady state. Category 3 rocks (61015, 62295) are subangular and cratered on only one side, but the crater frequency distributions have some of the characteristics of category 2 rocks. Category 4 rocks (15015, 15017, 15076, 60335) are angular, cratered on only one side, and have moderated to very low crater densities. The crater frequency distributions of categories 1 and 4 have properties indicating the possibility of estimating the time they were exposed to micrometeor bombardment. Category 1 rocks appear to have been exposed for 2 to 3 m.y. These rocks, particularly 68415, 68416, and 69935, may be ejecta from South Ray Crater, indicating an age of 2 to 3 m.y. for South Ray Crater. Category 4 rocks have been exposed for much shorter periods.

Morrison, D. A.↗
NASA NTRS1972

Results of examination of the returned Surveyor 3 samples for particulate impacts

The television housing and a section of the strut of the radar altimeter and Doppler velocity sensor were examined optically and with a scanning electron microscope for particulate impacts. The white surface of the camera was discolored during the months the Surveyor 3 was on the moon; however, most of the craters must have occurred as a result of lunar dust sandblasted by the LM exhaust. The polished section of the strut exhibits contamination which appears brown and seems to be partially composed of crystals. Electron microscopic analysis of the strut section indicated no craters of hypervelocity impact origin, confirmed pitting density results of the optical scans, and indicated that material in the craters is of lunar origin. No meteorite impacts larger than 25 microns were detected on the tubing section.

Cour-Palais, B. G.↗
NASA NTRS1972

Apollo window meteoroid experiment

The Apollo window meteoroid experiment is described which uses the Apollo command module heat shield window surfaces to obtain information about the flux of meteoroids with masses of 10 to the minus 7th power g and less; to examine the residue and the morphology of the craters produced by these meteoroid; to obtain information regarding the dynamic and physical properties of the meteoroids; and to discover possible correlations with the lunar-rock-crater studies. Photographs are included.

Cour-Palais, B. G.↗
NASA NTRS1972

Vapor phase crystallization in Apollo 14 breccia.

The vugs contained in many of the highly recrystallized breccias from Apollo 14 are discussed, along with the well-developed crystals of plagioclase, pyroxene, ilmenite, apatite, whitlockite, iron, nickel-iron, and troilite that extend from the vug walls and bridge open spaces. These crystals are interpreted as having formed by deposition from a hot vapor containing oxides, halides, sulfides, alkali metals, iron and possibly other chemical species. The hot vapor was associated with the thermal metamorphism and subsequent cooling of the Fra Mauro formation after it had been deposited as an ejecta blanket by the Imbrian impact.

Mckay, D. S.↗
NASA NTRS1972

Apollo 14 soils - Size distribution and particle types.

Particle size characteristics are discussed together with particle types, abundances, variation in the soils, questions of soil maturity, coarse fines, and ropy glasses. It is found that agglutinates are formed primarily by micrometeorite impact into lunar soil. Agglutinates appear to be the major particle type now being formed on the lunar surface. Agglutinate content of a soil increases with particle track densities and with surface exposure time.

Mckay, D. S.↗
NASA NTRS1972

Microcraters on lunar rocks.

Microcrater frequency distributions have been obtained for nine Apollo rocks and an exterior chip of an Apollo 12 rock. The frequency distributions indicate that five of the Apollo 14 rocks were tumbled more than once exposing different rock faces whereas four were not tumbled and represent a single exposure interval. The cumulative frequency of craters per square centimeter was extended below optical resolution limits using a SEM scan of an exterior chip of breccia 12073. No craters with central pit diameters less than 15 microns were seen in a total area of 0.44 sq cm. A detailed SEM scan of crystal faces and glassy crater liners revealed no microcraters equal to or larger than the resolution limit of 5 microns. An upper limit of 170 craters per sq cm with central pit diameters larger than 5 microns was set. The slope of the cumulative frequency curve for craters with central pit diameters less than about 75 microns is less than that obtained by other workers.

Morrison, D. A.↗
NASA NTRS1971

Lunar breccias

Lunar breccia, considering welded or sintered breccias, glassy breccias containing xenocrysts and xenoliths, instant rock breccias and recrystallized breccias

Mckay, D. S.↗
NASA NTRS1971

Apollo 12 soil and breccia

Apollo 12 lunar soil and breccia core tube and surface samples optical and electron microscope and microprobe analysis, relating data to geologic processes

Clanton, U. S.↗