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NASA NTRS1975

Nuclear chemistry of returned lunar samples: Nuclide analysis by gamma-ray spectrometry

Primordial and cosmogenic radionuclide concentrations are determined nondestructively by gamma-ray spectrometry in soil and rock samples from the returned Apollo 17 sample collection from Taurus-Littrow and Descartes. Geochemical evidence in support of field geology speculation concerning layering of the subfloor basalt flows is demonstrated along with a possible correlation of magmatic fractionation of K/U as a function of depth. The pattern of radionuclide concentrations observed in these samples is distinct due to proton bombardment by the intense solar flares of August 4-9, 1972. Such radionuclide determinations are used in determining lunar sample orientation and characterizing solar flare activity.

Okelley, G. D.↗
NASA NTRS1974

Lunar Science Conference, 5th, Houston, Tex., March 18-22, 1974, Proceedings. Volume 1 - Mineralogy and petrology. Volume 2 Chemical and isotope analyses. Organic chemistry. Volume 3 - Physical properties

Numerous studies on the properties of the moon based on Apollo findings and samples are presented. Topics treated include ages of the lunar nearside light plains and maria, orange material in the Sulpicius Gallus formation at the southwestern edge of Mare Serenitatis, impact-induced fractionation in the lunar highlands, igneous rocks from Apollo 16 rake samples, experimental liquid line of descent and liquid immiscibility for basalt 70017, ion microprobe mass analysis of plagioclase from 'non-mare' lunar samples, grain size and the evolution of lunar soils, chemical composition of rocks and soils at Taurus-Littrow, the geochemical evolution of the moon, U-Th-Pb systematics of some Apollo 17 lunar samples and implications for a lunar basin excavation chronology, volatile-element systematics and green glass in Apollo 15 lunar soils, solar wind nitrogen and indigenous nitrogen in Apollo 17 lunar samples, lunar trapped xenon, solar flare and lunar surface process characterization at the Apollo 17 site, and the permanent and induced magnetic dipole moment of the moon. Individual items are announced in this issue.

Gose, W. A.↗
NASA NTRS1974

Structural history of southeastern Mare Serenitatis and adjacent highlands

Deformational events are identified from Apollo 17 low-sun photographs of southern Mare Serenitatis and the adjacent Taurus-Littrow region. Analysis of the data indicates that the rate of deformation, including subsidence of the Serenitatis basin, has decreased through time as the crust increased in strength. Three main basalt sequences are found: one each at 3.8, 3.5, and 3.2 b.y. Wrinkle ridges began forming at about 2.5 b.y.; asymmetrical scarps also formed much later than the deformations.

Muehlberger, W. R.↗
NASA NTRS1974

Orange glass - Evidence for regional deposits of pyroclastic origin on the moon

Crystallized spheres of orange glass from Shorty Crater at the Apollo 17 site are shown by spectral reflectance data to be the characteristic ingredient of the dark mantling deposit of the Taurus-Littrow region. This deposit, mapped on spectral vidicon images taken using earth-based telescopes, apparently is thickest 50 km northwest of the Apollo 17 landing area, and has a gradational contact with the surrounding materials. The irregular areal distribution of the dark-mantle deposit and the gradational borders support conclusions based on laboratory studies of the orange soils that these are volcanic pyroclastic materials. Similar deposits are identified by spectral reflectance properties near Rima Bode, Schroeter W, Fauth H, and Higinus W. The same material is likely to occur at Sulpucius Gallus based on visual and photographic observations of orange soil. The apparently restricted occurrence of the orange-glass deposits in a belt along the edges of major mare basins implies structural control of volcanic vents and a possible deep-seated origin.

Adams, J. B.↗
NASA NTRS1974

Opaque mineralogy - Apollo 17, rock 75035

Rock 75035 is a medium-grained, holocrystalline, subophitic ilmenite basalt collected from the rim of Camelot Crater, and is believed to represent the subfloor basalts of the Taurus-Littrow valley. The rock consists of the major minerals pyroxene (45%), plagioclase (31%), and ilmenite (17%). Minor minerals include cristobalite (about 5%), troilite, native Fe, tranquillityite, baddeleyite, zirconolite, and rare ulvospinel. No olivine or armalcolite was observed in the specimen 75035,76. Mineralogically and chemically, as well as in age, this rock is similar to others collected from Camelot and other stations during the Apollo 17 mission. These rocks are almost identical to the Type B ilmenite basalts of Mare Tranquillitatis.

Meyer, H. O. A.↗
NASA NTRS1974

Petrography of Apollo 17 soils

An analysis of soils collected on the valley floor at Taurus-Littrow (dark mantle) reveals that these soils are formed by comminution of mare basalt flows and a clastic deposit consisting of black and orange glass spheres. There is no evidence for the pyroclastic origin of the dark mantle. It is found that the North Massif soils contain a large amount of mare-derived fragments being transported horizontally from the basaltic valley floor. A light mantle deposit of uniform composition including comminuted noritic and anorthositic breccia is observed. It is suggested that the light mantle is an avalanche deposit from regolith developed high on the South Massif.

Heiken, G.↗
NASA NTRS1974

Regolith compositions from the Apollo 17 mission

An investigation of the chemical, mineralogical, and petrographic data from six Apollo 17 regolith samples is summarized. The samples from the center of the Taurus-Littrow valley are very similar in composition and consist of mare basalt and a minor admixture (about 25%) of plagioclase-rich material. The material from Station 9 (Van Serg Crater) contains much less basalt and more breccia and are higher in Al2O3 and lower in TiO2 and FeO than the other mare sites. The chemical compositions of the samples from the North Massif, the South Massif, and the light mantle believed to be of landslide origin, are very similar and correspond to an olivine norite; the relatively high K2O and P2O5 content indicate the presence of a KREEP component. Additional results are described in detail.

Mason, B.↗
NASA NTRS1974

Origin of Apollo 17 rocks and soils

Lithophile trace element abundances have been determined by mass spectrometric isotope dilution for a suite of Apollo 17 samples. The six mare basalts have generally similar relative trace element abundances; they are also similar to Apollo 11 trace element poor basalts. It is suggested that these basalts were derived by partial fusion of cumulates. The Apollo 17 highland breccias show an order of magnitude range in trace element abundances although there is a clustering of KREEP-rich samples which are interpreted as mixtures. The Apollo 17 soils show only a limited range of trace element abundances. They are mixtures of highland breccias, mare basalts, and orange-black 'soil'. There appear to be two groups of soils, Light Mantle and the rest. Both groups seem to have the same basalt component, which is similar to Station 4 basalt from Shorty Crater and probably is the uppermost basalt unit throughout the Taurus-Littrow valley.

Philpotts, J. A.↗
NASA NTRS1974

Light element geochemistry of the Apollo 17 site

Abundances of C, N, S, He, H, and metallic iron at Taurus-Littrow are typical of a mixed mare and highland environment. Isotopic compositions of C, N, and S also generally conform to patterns observed elsewhere on the moon. Further evidence is presented for a complex lunar S cycle.

Petrowski, C.↗
NASA NTRS1975

Lunar atmospheric composition experiment

Apollo 17 carried a miniature mass spectrometer, called the Lunar Atmospheric Composition Experiment (LACE), to the moon as part of the Apollo Lunar Surface Experiments Package (ALSEP) to study the composition and variations in the lunar atmosphere. The instrument was successfully deployed in the Taurus-Littrow Valley with its entrance aperture oriented upward to intercept and measure the downward flux of gases at the lunar surface. During the ten lunations that the LACE operated, it produced a large base of data on the lunar atmosphere, mainly collected at night time. It was found that thermal escape is the most rapid loss mechanism for hydrogen and helium. For heavier gases, photoionization followed by acceleration through the solar wind electric field accounted for most of the loss. The dominant gases on the moosn were argon and helium, and models formed for their distribution are described in detail. It is concluded that most of the helium in the lunar atmosphere is of solar wind origin, and that there also exist very small amounts of methane, ammonia, and carbon dioxide.

Hoffman, J. H.↗
NASA NTRS1976

Early lunar magnetism

A new method (Shaw, 1974) for investigating paleointensity (the ancient magnetic field) was applied to three subsamples of a single, 1-m homogeneous clast from a recrystallized boulder of lunar breccia. Several dating methods established 4 billion years as the age of boulder assembly. Results indicate that the strength of the ambient magnetic field at the Taurus-Littrow region of the moon was about 0.4 oersted at 4 billion years ago. Values as high as 1.2 oersted have been reported (Collison et al., 1973). The required fields are approximately 10,000 times greater than present interplanetary or solar flare fields. It is suggested that this large field could have arisen from a pre-main sequence T-Tauri sun.

Banerjee, S. K.↗
NASA NTRS1976

H2CO emission at 2 millimeters in dark clouds

The paper reports the detection of the 2-mm emission line due to the 2(12)-1(11) transition of H2CO at two positions in the Taurus dark cloud and one position in the dark cloud L134 N. The profiles of the observed emissions are plotted, and peak radiation temperatures at 2 mm are determined for the three positions. These radiation temperatures are used along with data on the 2-mm H2CO absorption line and computed cross sections for H2-H2CO collisions to deduce the molecular hydrogen density and the ortho-H2CO column density in the two clouds. The results are shown to support previous theoretical estimates of the H2CO/H2 and the H2(C-12)O/H2(C-13)O ratios. It is concluded that if the abundances of CS and HCN in the clouds are equal to that of H2CO, emissions from these molecules should be easily detectable.

Evans, N. J., II↗
NASA NTRS1976

Lunar soil movement registered by the Apollo 17 cosmic dust experiment

The paper describes the Lunar Ejecta and Meteorites (LEAM) experiment of the Apollo 17 flight mission, placed in the Taurus-Littrow area of the moon. The objective of the experiment was to measure impact parameters of cosmic dust on the lunar surface. Preliminary data analysis led to the recognition that the bulk of events recorded by the LEAM experiment are not signatures of hypervelocity cosmic dust particles as expected, but are induced signatures of electrostatically charged and transported lunar fines.

Berg, O. E.↗
NASA NTRS1976

The kinetics of lunar glass formation, revisited

The nucleation frequency of Lunar Composition 70019, a lithified soil breccia from the center of a small crater in the Taurus-Littrow Valley, is determined using a relation that describes nucleation throughout the volume of a liquid together with measurements of the time required at temperatures of 780 to 930 C to obtain sensibly crystalline bodies. Curves indicating the time required at a given temperature to reach a particular fraction crystallized are shown to have the general form predicted by kinetic analysis. Nucleation frequencies are evaluated by applying such analysis to a curve representing the transition between glassy material and material with a sensible degree of crystallinity. The results obtained are found to be in excellent agreement with the values expected from the classical theory of homogeneous nucleation, indicating that such nucleation represents the dominant contribution to crystal formation, at least over the range of undercoolings covered (250 to 400 C).

Klein, L. C.↗
NASA NTRS1976

Rb-Sr ages and isotopic systematics of some Serenitatis mare basalts

Rb/Sr isotopic data and internal isochron ages are presented for some mare basalts from the Taurus-Littrow region. It is found that in age and in trace- and major-element chemistry as well as in Rb-Sr isotopic systematics, the Serenitatis mare basalts closely resemble the low-K Tranquility basalts, suggesting that over a wide region on the moon volcanism occurred at a discrete period 3.7-3.8 AE ago.

Murthy, V. R.↗
NASA NTRS1976

A solar origin for the large lunar magnetic field at 4.0 billion yr ago

A new method (Shaw, 1974) for paleointensity determination has been applied to three subsamples of one polymict breccia, 72215 (of age 4.0 billion yr) to yield an average paleointensity of 0.41 Oe at the Taurus-Littrow region of the moon around the time of breccia formation. Of the present models for lunar magnetism, only the Sonett and Runcorn (1974) model of a central iron core dynamo can explain the presence of such a large field in early lunar history. However, because of the similarity in size of this field and that for the early solar system deduced from carbonaceous chondrites, we draw attention to an apparently little-considered possibility: that the large magnetic field in early lunar history was external and solar in origin, and emanated from a pre-main sequence T-Tauri stage sun. Therefore, there should be no record of such a large magnetic field in lunar rocks younger than approximately 4.0 billion yr.

Banerjee, S. K.↗
NASA NTRS1977

Apollo 17 KREEPy basalt - A rock type intermediate between mare and KREEP basalts

The Apollo 17 KREEPy basalt is a unique lunar volcanic rock, observed only as clasts in the light friable breccia matrix (72275) of Boulder 1, Station 2 at Taurus-Littrow. Its status as a volcanic rock is confirmed by the absence of any meteoritic contamination, a lack of cognate inclusions or xenocrystal material, and low Ni contents in metal grains. The basalt was extruded 4.01 + or - 0.04 b.y. ago, approximately contemporaneously with the high-alumina mare basalts at Fra Mauro; shortly afterwards it was disrupted, probably by the Serenitatis impact, and its fragments emplaced in the South Massif. The basalt, which is quartz-normative and aluminous, is chemically and mineralogically intermediate between the Apollo 15 KREEP basalts and the high-alumina mare basalts in most respects. It consists mainly of plagioclase and pigeonitic pyroxene in approximately equal amounts, and 10-30% of mesostatis.

Ryder, G.↗
NASA NTRS1977

AR-39Ar-40 dating of basalts and rock breccias from Apollo 17 and the malvern achondrite

The principles and the potential of the Ar-39/Ar-40 dating technique are illustrated by means of results obtained for 12 Apollo 17 rocks. Emphasis is given to methodical problems and the geological interpretation of lunar rock ages. Often it is ambigious to associate a given lunar breccia with a certain formation, or a formation with a basin. In addition, large-scale events on the Moon have not necessarily reset radiometric clocks completely. One rock fragment has a well-defined plateau age of 4.28 b.y., but the ages of two Apollo 17 breccias define an upper limit for the formation age of the Serenitatis basin at 4.05 b.y. Ages derived from five mare basalts indicate cessation of mare volcanism at Taurus-Littrow approximately 3.78 b.y. ago. Ca/Ar-37 exposure ages show that Camelot Crater was formed by an impact approximately 95 m.y. ago. After a short summary of the lunar timetable as it stands at the end of the Apollo program, we report about Ar-39/Ar-40 and rare gas studies on the Malvern meteorite. This achondrite resembles lunar highland breccias in texture as well as in rare-gas patterns. It was strongly annealed at some time between 3.4 and 3.8 b.y. ago. The results indicate that very similar processes have occurred on the Moon and on achondritic parent bodies at comparable times, leading to impact breccias with strikingly similar features, including the retention of rare-gas isotopes from various sources.

Kirsten, T.↗