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At least 1,063 records · Page 59
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NASA NTRS1972

The Alhazen to Abul Wafa swirl belt: An extensive field of light colored, sinuous markings, part T

Problematic causes and characteristics of light colored sinuous markings on the lunar surface are explored. Two processes, exogenetic and endogenetic, are examined in detailed. During the endogenetic process it is suggested that impact ejecta deposition and surface disturbances cause the markings. During the endogenetic process, it is suggested that extrusive volcanism and sublimation and/or alteration cause the markings.

El-Baz, F.↗
NASA NTRS1973

Apollo 16 exploration of Descartes - A geologic summary.

The Cayley Plains at the Apollo 16 landing site consist of crudely stratified breccias to a depth of at least 200 meters, overlain by a regolith 10 to 15 meters thick. Samples, photographs, and observations by the astronauts indicate that most of the rocks are impact breccias derived from an anorthosite-gabbro complex. The least brecciated members of the suite include coarse-grained anorthosite and finer-grained, more mafic rocks, some with igneous and some with metamorphic textures. Much of the transverse area is covered by ejecta from North Ray and South Ray craters, but the abundance of rock fragments increases to the south toward the younger South Ray crater.

Source record↗
NASA NTRS1973

Lunar crater Copernicus - Search for debris of impacting body at Apollo 12 site.

In an attempt to characterize meteoritic material at the Apollo 12 site, 4 KREEP concentrates from soil 12033 have been analyzed by neutron activation analysis. These contain a meteoritic component in which siderophile Ir, Re, and Sb are depleted by about a factor of 2, while volatile Se, Zn, Ag, and Bi are depleted by a factor of more than 5 relative to Au. This pattern does not closely resemble any major chondrite or iron meteorite group, but is very similar to that observed in high-alkali samples from Apollo 14. The meteoritic component in KREEP at both sites is therefore predominantly derived from Imbrian ejecta. However, a second, small component of primitive composition seems to be present in Apollo 12 KREEP, judging from the slight, uniform enrichments in Ir, Re, Sb, and Zn relative to Au. This component does not seem to be due to micrometeorites. If it is attributed to the Copernican projectile, the crater Copernicus may have been formed by a cometary nucleus, 4 km in diameter, with an impact velocity of 30 to 40 km/sec. These conclusions depend critically on the assumption that the meteoritic component in Apollo 12 KREEP is representative of the entire impact.

Morgan, J. W.↗
NASA NTRS1972

Metamorphism of Apollo 14 breccias.

All Apollo 14 breccias for which thin sections are available (27 rocks) were studied petrographically. From one sample in each of six groups, electron microprobe analyses were performed on matrix (less than 25 microns) plagioclase, pyroxene, and olivine and of rims and cores of plagioclase and pyroxene clasts (50 to 300 microns). Matrix plagioclase, pyroxene, and olivine in the high-grade rocks display a narrow range of compositions, suggesting an equilibrated or metamorphic origin. However, in the low-grade rocks a wide range of compositions, suggesting a detrital or unequilibrated origin, is observed. Partially equilibrated states are observed in medium-grade samples. It is concluded that the Apollo 14 breccias formed as part of the Imbrium Basin ejecta blanket - the Fra Mauro formation. The continuous nature of the metamorphic series suggests that the medium- and high-grade breccias were derived from unmetamorphosed equivalents by autometamorphism in the thick, hot Fra Mauro formation at the Apollo 14 site.

Warner, J. L.↗
NASA NTRS1972

Chondrules in Apollo 14 samples and size analyses of Apollo 14 and 15 fines.

Chondrules have been observed in several breccia samples and one fines sample returned by the Apollo 14 mission. The chondrules are formed by at least three different processes that appear to be related to large impacts: (1) crystallization of shock-melted spherules and droplets; (2) rounding of rock clasts and mineral grains by abrasion in the base surge; and (3) diffusion and recrystallization around clasts in hot base surge and fall-back deposits. In the case of the Apollo 14 samples, the large impact almost certainly is the Imbrian event. Grain size analyses of undisturbed fines samples from the Apollo 14 site and from the Apollo 15 Apennine Front are almost identical, indicating that the two localities have similar meteoroid bombardment exposure ages, approximately 3.7 x 10 to the 9th yr. This observation is consistent with the interpretation that both the Fra Mauro formation and the Apennine Front material originated as ejecta from the Imbrian event.

King, E. A., Jr.↗
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

Compositional characteristics of some Apollo 14 clastic materials.

Eighty-two subsamples of Apollo 14 materials have been analyzed by instrumental neutron activation analysis techniques for as many as 25 elements. In many cases, it was necessary to develop new procedures to allow analyses of small specimens. Compositional relationships among Apollo 14 materials indicate that there are small but systematic differences between regolith from the valley terrain and that from Cone Crater ejecta. Fragments from 1-2 mm size fractions of regolith samples may be divided into compositional classes, and the 'soil breccias' among them are very similar to valley soils. Multicomponent linear mixing models have been used as interpretive tools in dealing with data on regolith fractions and subsamples from breccia 14321. These mixing models show systematic compositional variations with inferred age for Apollo 14 clastic materials.

Lindstrom, M. M.↗
NASA NTRS1972

Exposure ages and neutron capture record in lunar samples from Fra Mauro.

Cosmic-ray exposure ages of Apollo 14 rocks and rock fragments obtained by the Kr81-Kr83 method range from 27 to 700 m.y. Rock 14321, collected near the Cone crater rim, is one of the many approximately 27 m.y. old ejecta which were reported at the Third Lunar Science Conference. All the other rocks have considerably higher exposure ages. Isotopic anomalies from neutron capture in gadolinium, bromine, and barium are used to obtain information on the lunar neutron spectrum at various depths below the lunar surface. The flux ratio of resonance and slow (less than 0.3 eV) neutrons is found to be nearly constant in the topmost approximately 100 g/sq cm.

Lugmair, G. W.↗
NASA NTRS1973

Volatile elements in Apollo 16 samples - Possible evidence for outgassing of the moon.

Several Apollo 16 breccias, including one containing goethite, are strikingly enriched in volatile elements such as bromine, cadmium, germanium, antimony, thallium, and zinc. Similar but smaller enrichments are found in all highland soils. It appears that volcanic processes took place in the lunar highlands, involving the release of volatiles including water. The lunar thallium/uranium ratio is .0002 of the cosmic ratio, which suggests that the moon's original water content could not have exceeded the equivalent of a layer 22 meters deep. The cataclastic anorthosites at the Apollo 16 site may represent deep ejecta from the Nectaris basin.

Krahenbuhl, U.↗
NASA NTRS1973

Apollo 16 rocks - Petrology and classification.

The Apollo 16 rocks are classified in three broad intergradational groups: (1) crystalline rocks, subdivided into igneous rocks and metaclastic rocks, (2) glass, and (3) breccias, which are subdivided into five groups on the basis of clast and matrix colors. Most of the rocks were derived by impact brecciation of an anorthosite-norite suite but may represent ejecta from more than one major basin. First-cycle breccias are believed to have consisted of clasts of crushed anorthosite-norite in a fine-grained partly fused matrix with a chemical composition similar to that of the clasts. Most of the other recognized breccia types could have been produced by rebrecciation of first-cycle breccias.

Wilshire, H. G.↗
NASA NTRS1973

Do some of the sub-micrometer cosmic dust particles come from the sun.

Studies of cosmic dust particles collected at altitudes of 80 to 120 km over White Sands, New Mexico, and at times of noctilucent clouds over Kiruna, Sweden, indicate that an anomalously high atomic weight contribution is present within those particles collected at Kiruna. The elements observed are inconsistent with an origin due to atomic bomb fallout, meteoroidal crumbling, lunar ejecta, or comets. Many of these heavy elements may be stable in particulate form at the relatively high temperatures found in the coolest regions of the solar atmosphere. Some implications of the sun as the source of a significant component of cosmic dust are discussed.

Hemenway, C. L.↗
NASA NTRS1973

Meteoritic material on the moon.

Three types of meteoritic material are found on the moon: micrometeorites, ancient planetesimal debris from the 'early intense bombardment,' and debris of recent, crater-forming projectiles. Their amounts and compositions have been determined from trace element studies. The micrometeorite component is uniformly distributed over the entire lunar surface, but is seen most clearly in mare soils. It has a primitive, Cl-chondrite-like composition, and comprises 1-1.5% of mature soils. The ancient component is seen in highland breccias and soils more than 3.9 AE old. It has a fractionated composition, with volatiles depleted relative to siderophiles. The abundance pattern does not match that of any known meteorite class. The crater-forming component has remained elusive. Only a possible hint of this component has been seen, in ejecta from Dune Crater and Apollo 12 KREEP glasses of possibly Copernican origin.

Anders, E.↗
NASA NTRS1973

Extralunar materials in cone-crater soil 14141.

Radiochemical neutron activation analysis has been used to determine Ni, Zn, Ga, Ge, Cd, In, Ir, and Au in duplicate samples of lunar soil 14141 and in one additional replicate each of soils 14163 and 14259. The concentrations of extralunar trace elements Ni, Ge, Ir, and Au in 14141 and 14163 are, respectively, about 69 and 82% as high as those in 14259. Although most of the mass of 14141 appears to be ejecta from Cone Crater, a sizable contamination by mature Fra Mauro soil such as 14259 is also present. The siderophilic-element concentrations of the subregolith Fra Mauro materials are estimated to be 25 plus or minus 25% of those observed in 14259.

Wasson, J. T.↗
NASA NTRS1973

Studies related to the evolution of the lunar soil materials

Studies of the chemistry and morphology of the lunar samples are reported. The presence of fragments of plagoclase in the centers of the impact craters indicate that the glass spheres were derived by meteoritic impact from high velocity particles, while the glass was at high temperatures. From the study of the Apollo 16 samples, it is suggested that this material was formed in a hot impact ejecta blanket, or in an igneous environment, and later exposed to meteoritic impact. It is suggested that particles from Apollo 17 were formed in a cloud of siliceous vapors.

Carter, J. L.↗
NASA NTRS1973

Summary of scientific results

The accomplishments of the Apollo 17 flight are summarized. The basic objective of the mission was to sample basin-rim highland material and adjacent mare material and to investigate the geological evolutionary relationship between these two major units. The lunar experiments which were conducted include: (1) lunar field geology, (2) surface electrical experiments, (3) lunar traverse gravimeter experiments, (4) lunar seismic profiling experiment, (5) lunar ejecta and meteorites experiment, (6) analysis of lunar atmosphere composition, and (7) heat flow experiments.

Parker, R. A.↗
NASA NTRS1973

Preliminary geologic investigation of the Apollo 17 landing site

A geological investigation of the Apollo 17 lunar landing site was conducted. The Taurus-Littrow valley is interpreted as a deep graben formed by structural adjustment of lunar crustal material to the Serenitatis impact. Materials of the valley fill were sampled at many stations. Ejecta around many craters on the valley floor consist of basalt, showing that the graben was partly filled by lava flows. The geological objectives of the Apollo 17 mission are divided into orbital and lunar surface data collection. The data obtained for both types of investigation are presented in tables, photographs, and drawings.

Muehlberger, W. R.↗
NASA NTRS1973

Aitken crater and its environs

The physical characteristics of the fresh looking Aitken Crater and its surrounding environment are studied. Rim deposits and ejecta blanket indicate the crater has a probable impact origin or is formed during post-Aitken events. Data also indicate the crater's dark floor fill, its flow scarps, and smaller craters with domical structures are volcanic in origin. Landform varieties suggest episodic erruptions may also cause such craters.

El-Baz, F.↗
NASA NTRS1973

Current evolution of meteoroids

The observed mass distribution of meteoroids at 1 AU from the sun is briefly reviewed in a survey that ranges over the bulk of the mass spectrum from micrometeoroids to meteorite parent objects. The evolution of meteoroids under the influence of collisions, planetary perturbations, the Poynting-Robertson effect and radiation pressure is then discussed. Most micrometeoroids are expelled from the solar system by radiation pressure shortly after their production as secondary ejecta during impact by larger objects or as dust ejected by comets. Particles that survive will eventually be swept out by the Poynting-Robertson effect. Meteoroids in the radio and photographic ranges are destroyed in collisions faster than they can be replaced by the production of secondary fragments during collisions between larger objects.

Dohnanyi, J. S.↗