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NASA NTRS1978

Implications from Luna 24 sample 24170 to U-Pb evolution in the lunar mantle

The concentrations of U, Th and Pb, as well as the Pb isotopic composition, have been determined for a Luna 24 sample from the Mare Crisium area. A relatively recent disturbance to the U-Pb system during meteorite impact or burial in hot ejecta is suggested by the findings. According to three-stage U-Pb evolution model calculations, the source cumulates of the Luna 24 basalt evolved in a U-238/Pb-204 environment much lower than that of the Apollo mare basalts. A laterally heterogeneous lunar magma ocean, U-Pb fractionation during cumulate formation, and/or lack of KREEP addition to the Luna 24 basalt are also reflected in the calculations.

Unruh, D. M.↗
NASA NTRS1978

Luna 24 origins - Some trace element constraints

Luna 24 basaltic material originated in the particular volume of the lunar crust that produced Apollo 11 and Luna 16 basaltic material; it has the same Clr/P2O5 (r = residual) signature. Ru-Os contents (Barsukov et al., 1977) and a number of radiogenic age measurements place Luna 24 basalt origins stratigraphically in a layer between those from which Apollo 15 and Apollo 11 and 17 basalts were derived.

Jovanovic, S.↗
NASA NTRS1991

Wrinkle ridges in Lunae Planum Mars - Implications for shortening and strain

Photoclinometric data for Lunae Planum wrinkle ridges indicate average relief of about 130 m and distinct elevation discontinuities across the ridge of 55 m. Modeling ridges as the result of thrust faulting and associated upper-plate folding indicates shortening across individual ridges of about 131 m (90 percent faulting). Total shortening at 20 N across Lunae Planum is about 1840 m corresponding to a regional compressive strain of 0.29 percent. Strain appears uniform across Lunae Planum, although it is accommodated by larger and fewer structures in the west than in the east.

Plescia, J. B.↗
NASA NTRS1991

Searching for Crisium Basin ejecta - Chemistry and ages of Luna 20 impact melts

Chemical (INAA) and chronological (Ar-40 - Ar-39) analyses of six Luna 20 impact melts are performed, and these are compared to the results of Podosek et al. (1973), commonly taken to be representative of the Crisium Basin impact. At least two chemical groups of impact melts are identified. One is interpreted as melts derived from the local crust by craters over the last 3.9 Ga. Another group, which includes one of the samples dated by Podosek et al. (1973), is chemically and chronologically (3.85 + or - 0.02 Ga) indistinguishable from Apollo 17 samples interpreted as Serenitatis impact melts, and hence could be melt formed by that event and deposited at the Luna 20 site. One sample (22023,3,F) has a well-defined age of 3.895 + or - 0.017 Ga, and is chemically similar to, but distinct from, impact melts from other basins. This sample, and its chemistry and age are tentatively identified with the Crisium Basin impact. Whether the age of the Crisium impact is given by 22023,3,F, the samples analyzed by Podosek et al. (1973), or neither, it is clear that Crisium impact melt is not abundant in the Luna 20 collection.

Swindle, T. D.↗
NASA NTRS1971

Shock-metamorphic effects in the Luna-16 soil sample from Mare Fecunditatis

The results of intensive studies indicate that shock-metamorphic effects, characteristic of meteorite impact and virtually identical to those observed in Apollo samples, are common in fragments of the Luna-16 soil sample from Mare Fecunditatis. Two types of shock effects are present: (1) deformation and partial melting features in rock and mineral fragments (1-2 percent of fragments); and (2) heterogeneous glasses and glassy breccias produced by shock melting (70-80 percent of fragments). Shock effects were observed in pyroxene (deformation twin lamellae, multiple planar shock lamellae, extreme mosaicism, partial isotropization); in plagioclase (planar shock lamellae, complete isotropization to form maskelynite); and in basalt fragments (plagioclase isotropization, selective partial melting). The glasses exhibit several characteristics of shock melting, especially: (1) diversity in chemical composition; (2) association with shock mineral fragments and Ni-Fe spherules; and (3) heterogeneous schlieren and incipient fusion of mineral inclusions. Two types of source rocks are present in the Luna-16 sample; basaltic (85-90 percent) and feldspathic (10-15 percent). The basaltic rocks are predominant and generally occur as unshocked fragments, indicating that they form the bedrock underlying Mare Fecunditatis.

French, B. M.↗
NASA NTRS1971

Bulk, rare earth and other trace elements in Apollo 14 and 15 and Luna 16 samples

The chemical abundances were measured by instrumental and radiochemical neutron activation analysis in a variety of lunar specimens. Apollo 14 soils are characterized by significant enrichments of Al2O3, Na2O and K2O and depletions of TiO2, FeO, MnO and Cr2O3 relative to Apollo 11 and to most of Apollo 12 soils. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within approximately 200 m from the lunar module. Two Luna 16 breccias are similar in composition to Luna 16 soils. Four Apollo 15 soils (LM, STA 4, 9, and 9a) have variable compositions. Interelement correlations between MnO-FeO, Sc-FeO, V-Cr2O3 and K2O-Hf negate the hypothesis that howardite achondrites may be primitive lunar matter, argue against the fission hypothesis for the origin of the moon, and precludes any selective large scale volatilization of alkalies during lunar magmatic events.

Laul, J. C.↗
NASA NTRS1971

Petrological character of the Luna 16 sample from Mare Fecunditatis.

A total number of 1858 lithic and vitreous fragments from the Luna 16 core-tube sample are classified. The fragments were taken from soil fractions ranging in size from 150 to 425 microns at levels A and G. No important differences are observed between the proportions of particle types in levels A and G, nor between the soils of Luna 16 and those from the Apollo 11 landing site in the nearby Mare Tranquillitatis.

Wood, J. A.↗
NASA NTRS1972

Luna 16 - Relative proportions and petrologic significance of particles in the soil from Mare Fecunditatis.

Some 2380 lithic and vitreous particles from levels A and G of the Luna 16 core-tube sample were classified. The relative proportions of particle types from each of the two layers are reported, and some petrological and mineralogical aspects of the lithic and vitreous components of the lunar regolith are discussed. Possible sources of the particles in the Luna 16 soil are examined.

Reid, J. B., Jr.↗
NASA NTRS1972

Shock metamorphic effects in the Luna 16 soil sample from Mare Fecunditatis.

Diverse lunar soil fragments returned from the Luna 16 mission were examined for evidence in shock metamorphism in order to evaluate the role of meteorite impact in forming the lunar regolith at a new site relatively distant from the Apollo landing sites. It was found that shock metamorphic effects, characteristic of meteorite impact and virtually identical to those observed in Apollo samples, are common in the Luna 16 fragments. Two types of shock effects are present - i.e., a deformation and partial melting features in rock and mineral fragments, and heterogeneous glasses and glassy breccias produced by shock melting. It is concluded that these shock metamorphic effects indicate that regolith formation by meteorite impact has occurred in Mare Fecunditatis and is a general process over the entire moon.

French, B. M.↗
NASA NTRS1972

Luna 16 - An opaque mineral study and a systematic examination of compositional variations of spinels from Mare Fecunditatis.

The opaque mineralogy of the Luna 16 soil sample is studied, with an emphasis on a detailed survey of the compositional variations of the Fe-Ti-Cr-Al-Mg spinels. Analytical data are also presented for ilmenite. Textural characteristics and shock-metamorphic effects on the opaque minerals are briefly described and comparisons are made throughout between the Luna 16 samples and published and unpublished data on the Apollo samples.

Haggerty, S. E.↗
NASA NTRS1972

Rare gas studies in Luna 16-G-7 fines by stepwise heating technique - A low fission solar wind Xe.

Examination of He, Ne, Kr, and Xe in a dust sample (equal to or less than 125 micrometer) of Luna 16 in 12 temperature steps with especially small intervals in the low temperature range (80 C steps). The gas concentrations, as well as their relative abundances, are in general agreement with values reported by Vinogradov (1971) for Luna 16 and values found in Apollo 11 fines except for Ne. Comparison is made with various other experimental results. The solar wind Xe was lower in the fission-affected isotopes than was found in Apollo 11 fines and in the 1000 C fraction of the Pesyanoe meteorite as measured by Marti (1969). Air-Xe is interpreted as a fractional solar wind Xe with the composition found in this study.

Kaiser, W. A.↗
NASA NTRS1972

The geologic setting of the Luna 20 site.

Based on a study of the oblique portion of Apollo 16 panoramic photographs, a descriptions is presented of the geologic setting of the Soviet Luna 20 landing site. The complexly faulted terrain at this site has probably been involved in many generations of shattering and uplift produced by impacts which formed the large basin ring structures. Preliminary analysis of samples and photography indicates some similarities between the Luna 20 and Apollo 16 landing sites.

Heiken, G.↗
NASA NTRS1972

The chemical composition of soil from the Apollo 16 and Luna 20 sites.

The concentrations of the rare earth elements K, Rb, Sr, Ba, U, Zr, and Cr for the Luna 20 soil and four different Apollo 16 soils are reported. These trace element abundances imply: (1) that the lunar highlands consist of a mixture of rocks rich in large ion lithophile (LIL) elements and LIL-element improverished anorthosites; or (2) that the bulk of the aluminum-rich crust did not originate by upward segregation of plagioclase in a primitive liquid shell. The Luna 20 soil is distinguished from the Apollo 16 soil by lower aluminum and LIL element abundances.

Bansal, B. M.↗
NASA NTRS1973

Oxygen isotopic composition of the Luna 20 soil.

Comparison of the oxygen isotopic composition in the Luna 20 soil sample with the oxygen isotopic abundances of the Apollo 11, 12, 14, and 15 lunar soil samples. The Luna 20 soil is found to have a relatively low delta 0-18 content (0.57%) in comparison to the other lunar soils (0.58 to 0.63%).

Clayton, R. N.↗
NASA NTRS1973

Fossil track and thermoluminescence studies of Luna 20 material.

Track densities in 85 feldspar crystals from L-2009 range from 2,500,000 per sq cm to greater than one billion per sq cm. This track distribution represents an intermediate case between what have been previously defined as lightly and heavily irradiated soils and suggests that the Luna 20 sample consists of a mixture of a mature, heavily irradiated component with another, lightly irradiated component. Using a two-component mixing model, the age of the lightly irradiated component is about 270,000,000 yr. It is possible, but by no means certain, that this is associated with the formation of the crater Apollonius C. At about 200 C the ratio of natural thermoluminescence to that induced by a standard irradiation is similar to that in Apollo 12 and 14 cores below about 7 cm. This confirms that most of the Luna 20 sample represents subsurface material.

Crozaz, G.↗
NASA NTRS1973

The age and petrography of two Luna 20 fragments and inferences for widespread lunar metamorphism.

Ages were determined by the Ar-40/Ar-39 method on two metaclastic rocks returned from the lunar highlands north of Mare Fecunditatis by the Luna 20 probe. Both samples gave very well-defined argon retention ages of 3.90 plus or minus 0.04 AE which are indistinguishable from each other within a resolution of 0.02 AE. Both fragments, 22006 and 22007, are highly recrystallized polymict breccias; there is no evidence of radiogenic Ar-40, and the age almost surely dates the time of recrystallization. The cosmic ray exposure ages of these fragments are similar and high: 900 million years for 22006, 1300 million years for 22007. 22007 also contains substantial trapped argon with a high Ar-40/Ar-36. The Luna 20 results greatly extend the area of the moon's surface exhibiting a well-defined record of metamorphism at 3.9 AE. So far, lunar history in the interval from 4.6 to 3.9 AE is not preserved in the ages of surface rocks. This obliteration suggests lunar-wide metamorphic conditions occurring or terminating at this time as a result of major impacts.

Podosek, F. A.↗
NASA NTRS1973

Luna 20 soil - Abundance of 17 trace elements.

Review of the results of radiochemical neutron activation analysis of two Luna 20 fine soil and breccia samples for the abundance of 17 mainly siderophile and volatile elements that are strongly depleted in lunar surface rocks and hence represent sensitive indicators of meteoritic materials. These results are compared with those previously obtained for Apollo 16 soils. Some of the source rocks of Luna 20 regolith are identified.

Morgan, J. W.↗
NASA NTRS1973

A lunar differentiation model in light of new chemical data on Luna 20 and Apollo 16 soils.

Fines from a Luna 20 soil sample and from three Apollo 16 deep drill core samples have been analyzed for major-minor element abundances by a combined, semi-micro atomic absorption spectrophotometric and colorimetric method. Both the major element and large ion lithophile trace element abundances in these soils, the first from interior highland sites, are greatly influenced by the very high normative plagioclase content, being distinctly richer in Al and Ca, and poorer in K, P, Cr, Mn, Fe, and Ti, than most bulk soil samples from previous lunar missions. The relatively large compositional variations in the Apollo 16 core can be ascribed almost entirely to decreasing plagioclase with increasing depth. The chemical composition of the Luna 20 soil indicates less plagioclase and less KREEP than in the Apollo 16 soils. A lunar differentiation model is presented in which is made the suggestion that KREEP is the result of a second fusion event in a lunar crust consisting of early feldspathic cumulates and primary aluminous 'liquid.'

Nava, D. F.↗