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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The granulite suite: Impact melts and metamorphic breccias of the early lunar crust

The granulite suite consists of two major types of rocks. One is coarse-grained and poikilitic with many euhedral crystals of olivine and plagioclase. These characteristics indicate crystallization from a melt; the poikilitic granulites are impact melt breccias. The other group is finer-grained and granoblastic, with numerous triple junctions; the granoblastic granulites are metamorphic rocks. Compositional groups identified by Lindstrom and Lindstrom contain both textural types. Two pyroxene thermometry indicates that both groups equilibrated at 1000 to 1150 C. Calculations suggest that the granoblastic group, which has an average grain size of about 80 microns, was annealed for less than 6 x 10 exp 4 y at 1000 C, and for less than 2500 y at 1150 C. Similar equilibration temperatures suggest that both groups were physically associated after impact events produced the poikilitic melts. Granulitic impactites hold important information about the pre-Nectarian bombardment history of the Moon, and the composition and thermal evolution of the early lunar crust. Granulitic impactites are widely considered to be an important rock type in the lunar crust, but how they formed is poorly understood. Metal compositions and elevated concentrations of meteoritic siderophile elements suggest that most lunar granulites are impact breccias. Their occurrence as clasts in approximately 3.9 Ga breccias, and Ar-(40-39) ages greater than or = 4.2 Ga for some granulites show that they represent a component of the lunar crust which formed prior to the Nectarian cataclysm. Petrographic characteristics of lunar granulites indicate at least two endmember textural variants which apparently formed in fundamentally different ways. One type has granoblastic textures consisting of equant, polygonal to rounded grains, and abundant triple junctions with small dispersions around 120 degrees indicating a close approach to textural equilibrium. As suggested by many authors, granoblastic granulites probably formed by subsolidus annealing and recrystallization of fragmental or glassy protoliths. Examples of this type include 15418, 78155, and 79215. The other textural type consists of poikilitic to poikiloblastic rocks with euhedral to subhedral plagioclase and olivine enclosed by interstitial pyroxene. In some cases, the texture resembles that of an orthocumulate. Examples of this type include 60035, 67955, and 77017. Rounding of grain edges is common in poikilitic granulites, but the regular crystal shapes and widely dispersed dihedral angles show they are far from textural equilibrium. The textures of poikilitic granulites are more consistent with the formation of these rocks by crystallization from a melt than by subsolidus metamorphism. A few samples have been recognized with textural characteristics transitional between those of the granoblastic and poikiloblastic endmembers (e.g., 72559, 78527). Pyroxene compositions taken from the literature and determined for this study by electron microprobe were used to calculate equilibration temperatures. The Kretz Ca transfer (solvus) thermometer and the Lindsley and Anderson graphical method both give similar temperatures, which range from approximately 1000 to 1150 C. There is no apparent temperature difference between granoblastic and poikilitic varieties, but there is a hint in these data that the more ferroan varieties equilibrated to lower temperatures. Additional studies are in progress to test this possibility.

Cushing, J. A.↗
NASA NTRS1993

Impact-shocked zircons: Discovery of shock-induced textures reflecting increasing degrees of shock metamorphism

Textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously. However, planar deformation features (PDF) due to shock metamorphism are well documented in quartz and other mineral grains from these same environments. An etching technique was developed that allows scanning electron microscope (SEM) visualization of PDF and other probable shock-induced textural features, such as granular (polycrystalline) texture, in zircons from a variety of impact shock environments. These textural features in shocked zircons from K/T boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the U-Pb isotopic system.

Bohor, B. F.↗
NASA NTRS1997

Metamorphism of Cosmic Dust: Processing from Circumstellar Outflows to the Cometary Regolith

Nucleation is a non-equilibrium process: the products of this process are seldom the most thermodynamically stable condensates but are instead those which form fastest. It should therefore not be surprising that grains formed in a circumstellar outflow will undergo some degree of metamorphism if they are annealed or are exposed to a chemically active reagent. Metamorphism of refractory particles continues in the interstellar medium (ISM) where the driving forces are sputtering by cosmic ray particles, annealing by high energy photons and grain destruction in supernova generated shocks. Studies of the depletion of the elements from the gas phase of the interstellar medium tell us that if grain destruction occurs with high efficiency in the ISM, then there must be some mechanism by which grains can be formed in the ISM. Various workers have shown that refractory mantles could form on refractory cores by radiation processing of organic ices. A similar process may operate to produce refractory inorganic mantles on grain cores which survived the supernova shocks. Most grains in a cloud which collapses to form a star will be destroyed; many of the surviving grains will be severely processed. Grains in the outermost regions of the nebula may survive relatively unchanged by thermal processing or hydration. It is these grains which we hope to find in comets. However, only those grains encased in ice at low temperature can be considered pristine since a considerable degree of hydrous alteration might occur in a cometary regolith if the comet enters the inner solar system. Some discussion of the physical, chemical and isotopic properties of a refractory grain at each stage of its life cycle will be attempted based on the limited laboratory data available to date. Suggestions will be made concerning the types of experimental data which are needed in order to better understand the processing history of cosmic dust.

Nuth, Joseph A., III↗
NASA NTRS2005

Li, B - Behavior in Lunar Basalts During Shock and Thermal Metamorphism: Implications for H2O in Martian Magmas

Introduction: The water-content of Martian magmas is a topic of debate among researchers. Some Martian basalts are characterized with melt inclusions of biotite, apatite and amphibole; phases typically associated with hydration reactions on Earth [1-3]. However, the H-content of melt inclusions from these basalts is low, and bulk-rock H2O-contents range from a meager 0.013 to 0.035 wt. % in Shergotty [4]. Nonetheless, researchers note that low present-day water contents do not preclude a once hydrous past [5]. Since light lithophile elements (LLE), such as Li and B, partition into aqueous fluids at T > 350 C, workers proposed that Li-B depletions in pyroxene rims of Nakhlite and Shergottite basalts reflect the loss of several weight percent water from Martian magmas during crystallization [6]. Since similar depletions were observed in pyroxene rims from completely dry lunar basalts, it is likely that alternative mechanisms also contribute to the distribution of elements such as Li and B [7]. Given that many Martian basalts have experienced considerable shock pressures (15-45 GPa), it is possible that shock and subsequent thermal metamorphism may have influenced the volatile element records of these basalts [8]. In order to better understand the distribution of Li and B, we are studying the effects of crystal chemistry, shock pressure, and thermal metamorphism in pyroxenes from lunar basalts. Below, we discuss results from experimentally shocked and thermally metamorphosed Apollo 11, 10017 (A-11) and Apollo 17, 75035 (A-17) basalts.

Chaklader, Johny↗
NASA NTRS2014

The Effects of Thermal Metamorphism on the Amino Acid Content of the CI-Like Chondrite Y-86029

Carbonaceous chondrites con-tain a diverse suite of amino acids that varies in abundance and structural diversity depending on the degree of aqueous alteration and thermal histo-ry that the parent body experienced [1 - 3]. We recently determined the amino acid contents of several fragments of the Sutter's Mill CM2 chon-drite [4]. In contrast with most other CM2 chon-drites, the Sutter's Mill meteorites showed minimal evidence for the presence of indigenous amino acids. A notable difference between the Sutter's Mill meteorites and other CM2 chondrites are that the Sutter's Mill stones were heated to tempera-tures of 150 - 400 C [4], whereas most other CM2 chondrites do not show evidence for thermal met-amorphism [5]. Because empirical studies have shown that amino acids rapidly degrade in aqueous solutions above 150 C and the presence of miner-als accelerates this degradation [6], a plausible explanation for the lack of amino acids observed in the Sutter's Mill meteorites is that they were destroyed during metamorphic alteration. Fewer CI chondrites have been analyzed for amino acids because only a small number of these meteorites have been recovered. Nevertheless, indigenous amino acids have been reported in the CI chondrites Ivuna and Orgueil [7]. Here we report on the amino acid analysis of the CI-like chondrite, Yamato 86029 (Y-86029; sample size of 110 mg). Just as the Sutter's Mill meteorites were thermally metamporphosed CM2 chondrites, Y-86029 has experienced thermal metamorphism at higher temperatures than Orgueil and Ivuna (normal CI chondrites) experienced, possibly up to 600 C [8].

Burton, A. S.↗
DOE OSTI2025

Metamorphic Epitaxy Solutions for Thermophotovoltaic and Laser Power Conversion Applications

Metamorphic GaInAs enables photovoltaic devices optimized for a wide range of bandgaps between 0.35 and 1.41 eV. We have developed compositionally graded buffers made of GaInP and AlGaInAs to enable growth of these devices on GaAs substrates with low dislocation densities and high performance. We present results for devices grown on both graded buffer materials with device bandgaps in the range 0.58-1.41 eV and compare the benefits and drawbacks of each material system. These results enable high performance for applications such as thermophotovoltaics and optical power transmission using high power lasers.

III-V↗
DOE OSTI2025

SolAero 2020: III-V Metamorphic Graded Buffers (CRADA Final Report)

The effort by the National Renewable Energy Laboratory (NREL) for SolAero Technologies Corp (SolAero) will involve helping with four tasks: 1) Supporting the development, characterization, and optimization of metamorphic grades in III-V multi-junction solar cells, 2) Doping of III-V semiconductor materials and junctions, and 3) Incorporating strain balanced layers into solar cells, and 4) high efficiency germanium based solar cells.

14 SOLAR ENERGY↗