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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Refractory-element-rich inclusions in CM meteorites

Refractory-element-rich inclusions of a variety of types occur in CM meteorites. Based on detailed study of Murchison and more limited investigations of Murray, Nogoya, Cold Bokkeveld and Mighei, the most common of these inclusions are small spinel-hibonite bodies rimmed with diopside. Bulk chemical compositions are estimated to be approximately 67% Al2O3, 21% MgO, 5.5% CaO, 5.5% TiO2, and 1% SiO2. Although this chemical composition does not agree closely with current theoretically predicted compositions of early condensate assemblages, the inclusions have many features which suggest that they are indeed early condensates. These include texture, mineralogical composition, sequence of minerals and magnesium isotopic composition of hibonite. The CM refractory inclusions exhibit several differences from those observed in Allende and other CV meteorites. These probably record variations in time, place or physical conditions of origin for the two cases.

Macdougall, J. D.↗
NASA NTRS1979

Carbon dioxide electrolysis using a ceramic electrolyte

This paper discusses the results of an experimental study of the electrical aspects of carbon dioxide electrolysis using a ceramic electrolyte. The electrolyte compositions used in this study are 8% Y2O3 stabilized ZrO2, 7.5% CaO stabilized ZrO2, and 5% Y2O3 stabilized ThO2. Results indicate that the 8% Y2O3 stabilized ZrO2 is the best material to use for electrolysis, in terms of current as a function of voltage and temperature, and in terms of efficiency of oxide ion flow through it. The poorest results were obtained with the 5% Y2O3 stabilized ThO2 composition. An electrolysis system which might be employed to reclaim oxygen and carbon from effluents of space manufacturing, assuming that an industry would have to electrolyze 258,000 tonnes of CO2 per year, is predicted to require a total cell area of 110,000 sq m of 1 mm thickness and electrical capacity of 441 MW.

Erstfeld, T. E.↗
NASA NTRS1978

Chemistry of orange/black soils from core 74001/2

Double core 74001/2 soils were studied. Bulk soils and the 90-150 micrometer and less than 20 micrometer size fractions of 13 soils from the core for both major and trace elements by instrumental neutron activation analysis were analyzed. The orange and black glassy soils in the core 74001/2 are homogeneous in composition and due to their unusual compositional characteristics probably have derived from a single source with the same composition. The top of the core has been reworked to a depth of about 5 cm. The reworked layer is marked by compositional differences in the first 3 cm which reflect the addition (at least 10%) of materials including mare basalt and a CaO-rich component. The maturity profile (I sub s/FeO) clearly indicates reworking depth of about 5 cm. It is likely that at least some of the ferro-magnetically active component (including agglutinitic glass) has been 'inherited' with the added material.

Blanchard, D. P.↗
NASA NTRS1979

One atmosphere melting experiments on ilmenite basalt 12008

An evaluation of a crystal-fractionation model for Apollo 12 ilmenite basalts with melting experiments under controlled oxygen fugacities is reported. The crystallization sequence including olivine, chromium spinel, and pigeonite phases was determined, showing that the changes in melt composition are dominated by olivine crystallization and the decrease in MgO with a corresponding increase in CaO, Al2O3, and TiO2. It is concluded that the bulk composition of the ilmenite basalts was established by crystallization of olivine and minor spinel prior to the onset of pyroxene and plagioclase.

Rhodes, J. M.↗
NASA NTRS1980

Predicting major element mineral/melt equilibria - A statistical approach

Empirical equations have been developed for calculating the mole fractions of NaO0.5, MgO, AlO1.5, SiO2, KO0.5, CaO, TiO2, and FeO in a solid phase of initially unknown identity given only the composition of the coexisting silicate melt. The approach involves a linear multivariate regression analysis in which solid composition is expressed as a Taylor series expansion of the liquid compositions. An internally consistent precision of approximately 0.94 is obtained, that is, the nature of the liquidus phase in the input data set can be correctly predicted for approximately 94% of the entries. The composition of the liquidus phase may be calculated to better than 5 mol % absolute. An important feature of this 'generalized solid' model is its reversibility; that is, the dependent and independent variables in the linear multivariate regression may be inverted to permit prediction of the composition of a silicate liquid produced by equilibrium partial melting of a polymineralic source assemblage.

Hostetler, C. J.↗
NASA NTRS1974

High modulus invert analog glass compositions containing beryllia

Glass compositions having a Young's modulus of at least 15 million psi and a specific modulus of at least 110 million inches consisting essentially of, in mols, 10-45% SiO2, 2-15% Li2O, 3-34% BeO, 12-36% of at least one bivalent oxide selected from the group consisting of CaO, ZnO, MgO and CuO, 10-39% of at least one trivalent oxide selected from the group consisting of Al2O3, B2O3, La2O3, Y2O3 and the mixed rare earth oxides, the total number of said bivalent and trivalent oxides being at least three, and up to 10% of a tetravalent oxide selected from the group consisting of ZrO2, TiO2 and CeO2.

Bacon, J. F.↗
NASA NTRS1976

High modulus rare earth and beryllium containing silicate glass compositions

Glass compositions having a Young's modulus of at least 16 million psi and a specific modulus of at least 110 million inches consisting essentially of approximately, by weight, 20 to 43% SiO2, 8 to 21% Al2O3, 4 to 10% BeO, 27 to 58% of at least one oxide selected from a first group consisting of Y2O3, La2O3, Nd2O3, Ce2O3, Ce2O3, and the mixed rare earth oxides, and 3 to 12% of at least one oxide selected from a second group consisting of MgO, ZrO2, ZnO and CaO are described. The molar ratio of BeO to the total content of the first group oxides is from 1.0 to 3.0.

Bacon, J. F.↗
NASA NTRS1982

Containerless preparation of advanced optical glasses: Experiment 77F095

Containerless processing of optical glasses was studied in preparation for space shuttle MEA flight experiments. Ground based investigation, experiment/hardware coordination activities and development of flight experiment and sample characterization plans were investigated. In the ground based investigation over 100 candidate glass materials for space processing were screened and promising compositions were identified. The system of Nb2O5-TiO2-CaO was found to be very rich with containerless glass compositions and as extensive number of the oxides combinations were tried resulting in a glass formation ternary phase diagram. The frequent occurrence of glass formation by containerless processing among the compositions for which no glass formations were previously reported indicated the possibility and an advantage of containerless processing in a terrestrial environment.

Happe, R. A.↗
NASA NTRS1980

Predictions of mineral assemblages in planetary interiors

It is shown that mineral compatibilities in the model system CaO-MgO-Al2O3-SiO2 can be applied to deduce the mineral assemblages expected in planetary interiors and their variation with depth. In general, the available estimates of bulk composition of the terrestrial planets suggest that the terrestrial planets can be divided into two groups based on their predicted mineral assemblages. The terrestrial, Venusian, and lunar bulk compositions are expected to display the following sequence of mineral assemblages with increasing pressure: plagioclase lherzolite, spinel lherzolite, and garnet lherzolite. The sequences expected in Martian and Mercurian are different: spinel-plagioclase wehrlite, spinel lherzolite, and spinel-garnet wehrlite. These assemblages have a major influence on the compositions of liquids produced by melting of these planetary interiors, on the solidus temperatures, and thus on the nature of planetary differentiation and the types of magmas extruded at planetary surfaces.

Stolper, E.↗
NASA NTRS1982

Preliminary modeling of high pressure partial melting - Implications for early lunar differentiation

A quantitative model is presented for equilibrium crystallization of lunar magmas at high pressure, which, viewed in reverse, is equivalent to equilibrium partial melting. Data are extrapolated from simple systems, mare basalt systems, and from experiments on terrestrial compositions. Liquidus phase equilibria in a portion of the CaO-MgO-Al2O3-SiO2 system serve as a guide for predicting phase equilibria in the natural system. High pressure partial melting sequences are calculated for several proposed whole moon compositions at nominal pressure of 10 and 20 kb. Results show that compositions with chondritic Ca/Al have quite different melting paths from those with subchondritic Ca/Al, and as a result the types of magmas produced are quite different. If the moon possesses a chondritic Ca/Al ratio, models which rely on small degrees of partial melting to produce the early lunar magnetism are suspect.

Longhi, J.↗
NASA NTRS1982

A new LL3 chondrite, Allan Hills A79003, and observations on matrices in ordinary chondrites

Allan Hills A79003 is an LL3 chondrite with a petrologic subtype of 3.4 + or - 0.2. Contrary to previous suggestions, it is not paired with other Allan Hills specimens. It contains haxonite, (Fe,Ni)23C6; shock-melted, 'fizzed' metal-troilite intergrowths; and translucent, glassy-looking Huss matrix (fine-grained, Fe-rich silicate matrix), in addition to the normal opaque and recrystallized varieties of Huss matrix. Some chondrules are partly coated with opaque matrix, others with translucent matrix. Translucent matrix is more uniform in composition and contains less S, CaO and FeO and more MgO than the opaque variety. Both kinds of matrix rimmed chondrules before consolidation of the meteorite.

Scott, E. R. D.↗
NASA NTRS1982

Theoretical prediction of phase relationships in planetary mantles

Thermodynamic and phase equilibrium data are used to generate an internally consistent set of enthalpies and entropies for important components of the CaO-MgO-Al2O3-SiO2 (CMAS) system in silica-undersaturated compositions. The addition of Na and Fe(2+) to the CMAS system produces shifts in the plagioclase, spinel and garnet stability fields. While the Morgan and Anders (1979) model Martian composition has stability fields of plagioclase and garnet lherzolite, and a small spinel lherzolite field at temperatures below 900 C, the Martian mantle composition of McGetchin and Smyth (1978) would not contain orthopyroxene, and a low pressure assemblage of plagioclase-spinel wehrlite would be replaced by garnet-spinel wehrlite at higher pressure. In both cases, the Fe-Mg ratio would be substantially greater than that found in primitive terrestrial basalts.

Wood, B. J.↗
NASA NTRS1982

Experimental determination of the spinel-garnet boundary in a Martian mantle composition

The high pressure reaction orthopyroxene + clinopyroxene + spinel to garnet + olivine is applicable to the mantle of Mars. Experimental reversals of this reaction in the system CaO-MgO-FeO-Al2O3-SiO2 have been made in the range 1000-1200 C using the bulk composition proposed by Morgan and Anders (1980). At 1000 C, 1100 C, and 1200 C the garnet-out equilibrium is bracketed at 10.8 + or - 0.5, 12.6 + or - 0.5, and 15.2 + or - 0.5 kbars, respectively. A dP/dT slope of 14.0 bar/K at 1000 C increasing to 26.0 bar/K at 1200 C has been inferred. Depending on bulk composition, the mantle of Mars is inferred to have a phase assemblage of either olivine + clinopyroxene + orthopyroxene + garnet or olivine + clinopyroxene + garnet + spinel. In the second, the partial melts will not be buffered by olivine and orthopyroxene and will have markedly lower silica activities than those of the terrestrial mantle.

Patera, E. S.↗
NASA NTRS1983

The thermoluminescence carrier in the Dhajala chondrite

It is pointed out that the type 3 (unequilibrated) ordinary chondrites provide a major source of information on the early solar system. However, the interpretation of the data is difficult because all but a few display signs of metamorphic alteration. The present investigation is concerned with the thermoluminescence (TL) sensitivity measurements on 58 chondrules separated from the Dhajala meteorites. The data were discussed briefly by Sparks and Sears (1982). In the current investigation particular attention is given to the constraints placed by these data on the mechanism by which metamorphism is related to TL sensitivity. Dhajala-normalized TL sensitivity of the separated chondrules is plotted against chondrule mass, and a histogram of the CaO contents of 15 chondrules is presented. Histograms showing the TL sensitivity of chondrules separated from the Dhajala meteorite are also provided.

Sparks, M. H.↗
NASA NTRS1982

The lunar regolith - Chemistry, mineralogy, and petrology

The data base on the lunar regolith is surveyed to form a synthesis of the lunar regolith chemistry, mineralogy, and petrology. The data were derived from samples collected by the Apollo missions 11-17 and the Luna 16, 20, and 24 probes. The missions were sent to sample formations and areas which typified the common observed features of the lunar surface. Drive tubes were used to extract samples from beneath the surface in order to study the relationship between the regolith and the bedrock, as well as to identify the processes that formed the regolith, which is regarded as the prime source of raw materials for early lunar industrial activities. Regolith origins are now understood to be destructive processes of comminution and constructional processes of agglutinate formation. Mixing occurs on the local scale, although lateral transport is inefficient on the moon. The usual contents of the fraction of regolith less than 10 microns in diameter are Al2O3, CaO, Na2O, K2O, light REE, and Th.

Papike, J. J.↗
NASA NTRS1983

Stillwater anorthosites - A lunar analog?

Samples of anorthosite from Stillwater complex units AN-I and AN-II have been studied by instrumental neutron activation analysis for FeO, CaO, Na2O, REE, and other trace elements, and the results are discussed. No systematic variations of chemical composition with stratigraphic position were observed. The major and trace compositions of both units appear to be identical, with plagioclase compositions virtually constant throughout both. Thus, there is almost no evidence for evolution of parent magma composition during the genesis of these units. The bulk of the anorthosites appear to consist of cumulus-adcumulus plagioclase and pyroxene. Very little trapped liquid component was found. The chemical elements are not normally or lognormally distributed among samples taken from either anorthosite unit. The irregular distribution of pyroxene oikocrysts indicates that interstitial melt migrated substantially prior to final consolidation of the rock.

Salpas, P. A.↗
NASA NTRS1983

Temperatures of shock-induced shear instabilities and their relationship to fusion curves

New emission spectra for MgO and CaAl2Si2O8 (glass) are observed from 430 to 820 nm. Taken with previous data, it is suggested that transparent solids display three regimes of light emission upon shock compression to successively higher pressures: (1) characteristic radiation such as observed in MgO and previously in other minerals, (2) heterogeneous hot spot (greybody) radiation observed in CaAl2Si2O8 and previously in all transparent solids undergoing shock-induced phase transformations, and (3) blackbody emission observed in the high pressure phase regime in NaCl, SiO2, CaO, CaAl2Si2O8, and Mg2SiO4. The onset of the second regime may delineate the onset of shock-induced polymorphism whereas the onset of the third regime delineates the Hugoniot pressure required to achieve local thermal equilibrium in the shocked solid. It is also proposed that the hot spot temperatures and corresponding shock pressures determined in the second regime delineate points on the fusion curves of the high pressure phase.

Schmitt, D. R.↗
NASA NTRS1984

Two forsterite-bearing FUN inclusions in the Allende meteorite

Two forsterite-, fassaite-, spinel-rich inclusions in Allende which share common mineralogy and texture with three previously described inclusions are described. These inclusions were at least partially molten at temperatures over 1400 C, and their crystallization sequence was spinel, olivine, fassaite, and Mg-rich melilite. At least some of them experienced partial volatilization of MgO and SiO2 from their outer margins. At least one of the inclusions is highly enriched in MgO relative to CaO and Al2O3 compared to Allende coarse-grained inclusions, although it is just as strongly enriched in refractory trace elements as the latter, relative to C1 chondrites. Two of the objects are FUN inclusions on the basis of their oxygen, magnesium, and silicon isotopic compositions.

Clayton, R. N.↗