SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
MacAlpine Hills 88104 and 88105 meteorites found in nearby locations in Antarctica, which are considered to be pieces of the same meteorite, are described. MAC88104/5 is an anorthositic breccia consisting of numerous small clasts in a glassy matrix. A summary list of lunar meteorites and a review of consortium research are presented.
Parameterizations have been developed for impact glass compositions which makes its possible to acquire geochemical information about pre-impact target materials. The impact glass populations among unrelated highland regoliths including Apollo 16 regolith 64001 and the lunar meteorites ALHA81005 and MAC88105 have been compared. It is concluded that the Apollo 16 impact glasses are compositionally more diverse than those in the lunar meteorites. This diversity reflects the complex geology of the Apollo 16 region, in which extensive exposures of mare basalts occur within 300 km. Apollo 16 regolith 64001 contains a distinctive subset of impact glasses with major element compositions similar to lunar highland meteorite. These impact glasses (less than 100 micrograms) indicate that the lunar highlands are geochemically more diverse than the compositional range currently represented by large (more than 1 gram) samples. Lunar impact glasses provide geochemical constraints on the full range of regolith compositions that occur on the moon.
The MAC88105 lunar meteorite, as represented by thin section 78, contains three major types of impact melt breccias. The most abundant type is clast-laden, fine-grained, and rich in Al2O3 (28 wt pct); these clasts constitute most of the meteorite. Their abundance and aluminous nature indicate that the MAC88105 source area was very aluminous. This is consistent with formation of the primordial lunar crust from a global magma ocean. The second type of impact melt is represented by only one clast in 78. It has a basaltic bulk composition similar to many other lunar impact melts, but is significantly richer in P2O5 than most and has a much lower MgO/(MgO + FeO). The third impact-melt type resembles a prominent melt group at Apollo 16, but has lower MgO/(MgO + FeO). These data show that basaltic impact melts are compositionally diverse. Dating samples of the Al-rich impact melts and the new types of basaltic impact melts from this meteorite can test the idea that the Moon suffered a terminal cataclysm 3.9 Ga ago.
To determine the chemical characteristics of the MAC88104/5 meteorite six thin sections and three bulk samples were analyzed by electron microprobe and instrumental neutron activation. It is concluded that this meteorite is dominated by lithologies of the ferroan anorthosite suite and contains abundant granulitized highland clasts, devitrified glass beads of impact origin, and two small clasts of basaltic origin. It is suggested that one of these basaltic clasts, clast E, is mesostasis material, and clast G is similar to the very low-Ti or low-Ti/high-alumina mare basalts. Impact melt clasts MAC88105, 69, and 72 have major and trace element compositions similar to the bulk meteorite.
The feasibility of using Sm-147 and Sm-146 as chronometers was investigated using Sm-Nd data obtained on three meteorites: Ibitira, Morristown, and Acapulco. The results of isotope analyses demonstrate the presence of in situ decay of short-lived Sm-146 in these meteorites with initial abundances of Sm-146/Sm-144 between 0.009 and 0.007 in different meteorites. Precisely defined Sm-147/Nd-143 internal isochrons were obtained yielding ages equal to 4.46 +/-0.02 AE for Ibitira, 4.47 +/-0.02 AE for Morristown, and 4.60 +/-0.03 AE for Acapulco. However, detailed examination of the coupled Sm-147/Nd-143 and Sm-146/Nd-142 parent-daughter systematics and of initial Nd-143/Nd-144 values indicated the presence of inconsistencies in the data in spite of the precise isochrons, indicating the need for care in the interpretation of the parent-daughter systematics, even when they appear well behaved.
The meteoritic evidence for a T Tauri phase in the sun's evolution is reviewed. Emphasis is given to effects recorded in meteoritic grains before final compaction of the meteorite parent body and the evidence that these precompaction irradiation effects do or do not require an active early sun. Several other effects attributed to such early activity are also reviewed.
Visible and near-IR observations are reported which confirm that Apollo asteroid 3103 (1982 BB) is a high-albedo E-type object with a reflectance spectrum consistent with the iron-free silicates, primarily enstatite, present in the aubrites. Visible and thermal IR light curves indicate that 3103 is an elongated object with no evidence of substantial surface albedo variations. It is presently in an orbital resonance with earth and is probably a relatively long-lived member of the earth-approaching population. This is consistent with the relatively long cosmic ray exposure ages of the aubrites compared to other stony meteorites. The fall geometries of the aubrites are consistent with their being derived from 3103. The ubiquitous brecciated nature of the aubrites and the indications of a single parent body for nearly all these meteorite suggest that 3103 is the sole near-earth parent body of this meteorite type.
The stony iron model of S asteroids is examined using recently measured telescopic reflectance spectra of 40 S asteroids and laboratory spectra of six primitive achondrites and an iron meteorite. It is concluded that 40 percent of well-measured reflectance spectra of the S asteroids can be fitted by the model composed of an iron meteorite and six representative primitive achondrites. The hypothesis that the S asteroids are composed of primitive achondrites strongly bound together by metallic iron networks can explain the extremely small population of primitive achondrites in meteorite collections. If all the larger asteroids initially formed of ordinary chondritelike source materials were altered to S-asteroids, the apparent absence of ordinary chondrites in the main belt may be due to the fact that they are too small to have their reflectance spectra measured.
The structure and chemical composition of the Lafayette meteorite were examined using several methods. The meteorite contains abundant hydrous post-magnetic alteration material consisting of ferroan smectite clays, magnetite, and ferrihydrite. The textural relations, mineralogy, and composition of these materials were examined and their preterrestrial nature was documented. Olivine, pyroxene, and glass alteration are described and the bulk compositions of the alteration veinlets is discussed. Essential features of the geochemistry of the alteration processes are described. It is suggested that the alteration of the Lafayette meteorite occurred during episodic infiltrations of small volumes of saline water. Constraints placed on water chemistry and water-rock interactions in the Martian crust are outlined.
We have performed Mossbauer spectroscopy on two different pieces of the meteorite Zagami belonging to the group of SNC meteorites. In one of the samples we found a substantial amount of olivine inter grown with one kind of pyroxene, and also another kind of pyroxene very similar to the pyroxene in the other sample we examined. Both samples showed less than 1 percent of Fe(3+) in the silicate phase. The group of SNC meteorites called shergottites, to which Zagami belongs, are achondrites whose texture, mineralogy and composition resembles those of terrestrial diabases. The results from the investigation are presented.
We report here the discovery of a recent meteorite shower in Antarctica, the members of which have very high natural thermoluminescence levels. It is apparent from these data that the shower has been on Earth only a short time (approximately 1000 years) and the meteorite probably came to Earth through rapid (less than 10 exp 5 years) evolution from an orbit with perihelion greater than 1.1 AU, similar to Amor asteroids. Only a very small number of meteorites, including a few modern falls, appear to have had similar orbital histories.
The magnetic properties of extraterrestrial materials, in particular natural remanent magnetization (NRM), is a potentially useful study for detecting ancient Solar System magnetic fields and for elucidating meteorite evolutionary processes. Results are presented for the following: howardites--Kapoeta, Petersburg, Le Teilleul, and EET 87503; eucrites--Sioux County and Millbillillie; and diogenites--Shalka and Johnstown. Significant features of their magnetism are within-sample in homogeneity of NRM directions in several of the meteorites and within-sample uniformity of axes of an isotropy of magnetic susceptibility. Both these phenomena bear on the meteorites' evolution and the timing of the magnetization process.
Enstatite meteorites have proven to be ideal samples for past studies of the I-Xe system. This work focuses on two enstatite meteorites that were formed by impact processes. Ilafegh 009 is a clast-free impact melt rock from the EL chondrite parent body. The Shallowater aubrite likely formed when a fully molten planetesimal collided with a solid planetesimal, mixing fragments of the solid planetesimal into the enstatite mantle of the molten planetesimal. A complex three-stage cooling history resulted from this mixing and later break-up and reassembly of the parent body. The present study indicates that the I-Xe structure of these two meteorites resulted from in situ decay of live I-129 and that both experienced xenon closure of the iodine host phase at approximately the same time. I-Xe cooling rates are consistent with the cooling rates derived from mineralogic and petrologic studies of these objects. The similarities in ages suggest that the region of the nebula in which enstatite parent bodies formed must have experienced an intense early bombardment.
The bulk chemical composition of meteorites has been suggested as a main factor influencing the production of cosmogenic nuclides. Numerical simulations with Los Alamos Monte Carlo production and transport codes were done for Ne-21/Ne-22 ratios and Ar-38 production rates in meteorites with a wide range of compositions. The calculations show that an enhanced flux of low-energy secondary particles in metal-rich phases is the essential key for the explanation of experimentally observed differences in nuclide production processes in various meteorite classes.
The Elephant Moraine meteorite EET 87521 was classified as a lunar mare basalt breccia which is composed mainly of VLT basalt clasts. Here we report on our petrological study of lithic clasts and monomineralic fragments in the thin sections EET 87521,54 and EET 87521,47,1, which were prepared from the meteorite. The results of the study show that EET 87521 consists mainly of Al-rich ferrobasalt clasts and olivine pyroxenite clasts. The bulk composition of the meteorite can be well modelled by the mixing of these lithic components which appear to be differentiates of the Luna 25 basalt melt. KREEP and Mg-rich gabbro components are minor constituents of EET 87521.
What could be more exciting than seeing pieces of other worlds? The Apollo program left a legacy of astounding accomplishments and precious samples. Part of the thrill of those lunar missions is brought to schools by the lunar sample educational disks, which contain artifacts of six piloted trips to the Moon. Johnson Space Center (JSC) is preparing 100 new educational disks containing pieces of meteorites collected in Antarctica. These represent chunks of several different asteroids, that were collected in one of the most remote, forbidding environments on Earth. These pieces of the Moon and asteroids represent the products of basic planetary processes (solar nebular processes, initial differentiation, volcanism, and impact), and, in turn, these processes are controlled by basic physical and chemical processes (energy, energy transfer, melting, buoyancy, etc.). Thus, the lunar and meteorite sample disks have enormous educational potential. New educational materials are being developed to accompany the disks. Present materials are not as effective as they could be, especially in relating samples to processes and to other types of data such as spectral studies and photogeology. Furthermore, the materials are out of date. New background materials will be produced for teachers, assembling slide sets with extensive captions, and devising numerous hands-on classroom activities to do while the disks are at a school and before and after they arrive. The classroom activities will be developed by teams of experienced teachers working with lunar and meteorite experts.
U-Th-Pb, Sm-Nd, and (Ar-40)-(Ar-39) isotopic studies were performed on Yamato (Y)-793169, an unbrecciated diabasic lunar meteorite whose chemical composition is close to low Ti(LT) and very low-Ti (VLT) mare basalts. The isotopic data indicate that the meteorite was formed earlier than 3.9 Ga from a source with low U/Pb and high Sm/Nd and was distributed by a thermal event at 751 Ma. due to the small sample size (104 mg), a plagioclase crystal and glass grains were handpicked for Ar analysis, leaving four fractions for the U-Th-Pb and Sm-Nd studies; a fine-grained fraction (less than 63 microns; Fine) and three medium-grained fractions (63-150 microns). Medium-grained fractions were divided by density; a heavy fraction (rho greater than 3.3) consisting mainly of pyroxene (PX1), a lighter fraction (rho less than 2.8) consisting of plagioclase (PL), and a middle density fraction (predominantly pyroxene; PX2). The fractions were washed with acetone and alcohol, and then leached in 0.01 HBr and 0.1N HBr in order to remove any terrestrial Pb contamination. Analysis of the HBr leaches revealed that this meteorite was heavily contaminated with terrestrial Pb during its residence in Antarctic ice.
Multivariate statistical analysis techniques (linear discriminant analysis and logistic regression) can provide powerful discrimination tools which are generally unfamiliar to the planetary science community. Fall parameters were used to identify a group of 17 H chondrites (Cluster 1) that were part of a coorbital stream which intersected Earth's orbit in May, from 1855 - 1895, and can be distinguished from all other H chondrite falls. Using multivariate statistical techniques, it was demonstrated that a totally different criterion, labile trace element contents - hence thermal histories - or 13 Cluster 1 meteorites are distinguishable from those of 45 non-Cluster 1 H chondrites. Here, we focus upon the principles of multivariate statistical techniques and illustrate their application using non-meteoritic and meteoritic examples.