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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Convection cells in the early lunar magma ocean - Trace-element evidence

A method was proposed for recognizing suites of samples which are related to the differentiation of distinct and regionally separated magmas in the early lunar surface ocean. The sample suites were identified by three Cl-P2O5 compositional groups. New experimental data continue to add samples to these groups. Each magma was associated with a convection cell the boundaries of which are proposed. Independent geochemical evidence supporting a limited number of early magmas is cited. Two new possible Cl-P2O5 groups are identified. Samples not indigenous to a given site and their possible source regions are identified. It is proposed that many Apollo 17 basalts are not locally derived.

Jovanovic, S.↗
NASA NTRS1976

Trace element evidence regarding a chondritic component in howardite meteorites

The concentrations of siderophiles Ni, Ge, Ru, Ir, and Au and volatiles Zn, Ga, Cd, and In in howardite meteorites were determined and are discussed along with similar data for eucrites and diogenites. The concentrations of the chondritic component in howardites are remarkably high. The concentrations in four high-siderophile howardites are comparable to those found in mature soils from the lunar highlands. The amounts of excess volatiles are roughly consistent with those expected if the chondritic component resemble CI, CM, or E4 chondrites. Evidence indicates that the howardite parent body had a radius of several hundred kilometers, and the most probable formation location was 1-2 AU from the sun.

Chou, C.-L.↗
NASA NTRS1978

Trace elemental characteristics of aerosols emitted from municipal incinerators

As part of a continuing investigation of high temperature combustion aerosols, elemental composition of size differentiated aerosols emitted from a local municipal incinerator was studied. Aerosols were aerodynamically separated into eight diameter groups ranging from 0.43 mm to 20 mm, collected, and analyzed by charged particle induced X-ray emission technique. On line data collection and reduction codes generated aerial densities for elements from Na to U with sensitivities in the ng/cu m range for most elements. From the total weights of aerosols collected per stage, their size distribution was determined to be bimodal, with one group centered at a diameter of 0.54 mm and the other at a diameter of 5.6 mm. Measured elemental concentrations in various size ranges indicate that K and S show a strong tendency to concentrate on aerosol surfaces. A weaker trend for surface preference was also observed for Mn and Ni, but other elements show no such trend.

Singh, J. J.↗
NASA NTRS1977

Rare earth and trace element geochemistry of a fragment of Jurassic seafloor, Point Sal, California

Rocks from an ophiolite suite once on the seafloor were analyzed for rare earth elements (REE), Sc, Co, Na2O, Cr, Zn and FeO. Strontium isotope exchange noted in some of the lavas is attributed to basalt-seawater interaction; the Ce abundance in smectite- and zeolite-bearing lavas may also be due to prolonged exposure to seawater. The higher grades of metamorphic rock, however, show no variation from the usual flat or slightly light REE depleted profiles. Plutonic igneous rock, all light REE depleted, have total REE abundances varying by a factor of 100 between the dunites and diorites. In order of decreasing REE abundance are hornblende, clinopyroxene, plagioclase, orthopyroxene and olivine. Calculations of REE contents of liquids in equilibrium with early cumulative clinopyroxenes suggest that the parent to the stratiform sequence was more depleted in light REE than the parent to the lava pile.

Menzies, M.↗
NASA NTRS1977

Trace element distribution in mineral separates of the Allende inclusions and their genetic implications

Concentrations of the rare earth elements (REE), Sc, Co, Fe, Zn, Ir, Na, and Cr were determined for mineral separates of the coarseand fine-grained types (group I and II) of the Allende inclusions. These data in combination with other data suggest that the minerals in the coarse-grained inclusions (group I) crystallized in a closed system with respect to refractory elements although a totally molten stage is precluded. The data also indicate that fine-grained (group II) inclusions were formed by condensation from a super-cooled nebular gas; REE-rich clinopyroxene and spinel were formed earlier than REE-poor sodalite and nepheline. In addition, pre-existing Mg isotope anomalies in the coarse-grained inclusions must have been erased during the heating stage.

Nagasawa, H.↗
NASA NTRS1978

A 'chondritic' eucrite parent body - Inference from trace elements

Thirty-three elements were analyzed by radiochemical and instrumented neutron activation in four eucrites - Juvinas (brecciated), Ibitira (vesicular, unbrecciated) and Moore County and Serra de Mage (both cumulate, unbrecciated). Nebular and planetary effects are distinguished in the C1-normalized abundance patterns arranged in the order of volatility. Lithophile, chalcophile, and siderophile patterns are discussed; the stepped lithophile pattern reveals the dominance of nebular processes while the siderophile pattern retains little sign of nebular processes and instead reflects planetary metal-silicate partition. Volatiles were apparently accreted as a fractionated C3-like component, and consistent but subtle C1-normalized abundance differences between eucrites result from crystal/liquid differentiation.

Morgan, J. W.↗
NASA NTRS1978

Further studies of trace elements in C3 chondrites

Five carbonaceous chondrites (Renazzo C2V, Allende C3V, Ornans C3O, Warrenton C3O, and Orgueil C1) were analyzed by radiochemical neutron activation analysis for 20 elements. Elements condensing between approximately 700 and 420 K are systematically more depleted than those condensing between 1000 and 900 K, and the depletion correlates inversely with matrix content and directly with degree of metamorphism. A model of gas-dust fractionation during condensation, by settling of dust to the median plane of the nebula, is proposed. Gas/dust ratios relative to the cosmic ratio ranged from 0.7 at 1000 K to 0.5 at 700 K for C3O chondrites that accreted first and from 1.3 to 0.6 for the last. No further gas/dust fractionation was indicated below 700 K

Takahashi, H.↗