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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Hg and Pt-metals in meteorite carbon-rich residues - Suggestions for possible host phase for Hg

Carbon-rich and oxide residual phases have been isolated from Allende and Murchison by acid demineralization for the determination of their Hg, Pt-metal, Cr, Sc, Co, and Fe contents. Experimental procedures used eliminated the possibility of exogenous and endogenous contaminant trace elements from coprecipitating with the residues. Large enrichments of Hg and Pt-metals were found in Allende but not in Murchison residues. Hg-release profiles from stepwise heating experiments suggest a sulfide as the host for Hg. Diffusion calculations for Hg based on these experiments indicate an activation energy of 7-8 kcal/mol, the same as that for Hg in troilite from an iron meteorite. This is further support for a sulfide host phase for Hg. Equilibration of Hg with this phase at approximately 900 K is indicated. Reasons for the presence of Pt-metals in noncosmic relative abundances are explored.

Jovanovic, S.↗
NASA NTRS2005

LA-ICP-MS Study of Trace Elements in the Chanuskij Metal

This progress report covers work done during the second year of the 3-year proposal. During this year we resolved many issues relevant to the analytical technique developed by us for measuring trace elements in meteoritic metals. This technique was used to measure concentrations of Fe, Ni, Co, Cr, Cu, Ga, Ge, As, Mo, Ru, Rh, Pd, Sb, W, Re, Os, Ir, Pt, and Au in eight large (120 - 160 microns) metal grains from both "igneous" and "metamorphic" lithologies of the Chanuskij silicate inclusions. The first application of OUT technique to metal grains from thin sections showed some limitations. Small thickness of metal grains in the thin section limited the signal to 3-4 time-slices instead of 10- 1 1 ones in polished sections of iron meteorites studied before.

Petaev, Michail I.↗
NASA NTRS1990

Electrochemical measurements and thermodynamic calculations of redox equilibria in pallasite meteorites - Implications for the eucrite parent body

The intrinsic oxygen fugacity (IOF) of olivine separates from the Salta, Springwater, and Eagle Station pallasites was measured between 850 and 1150 C using oxygen-specific solid zirconia electrolytes at 100,000 Pa. Thermodynamic calculations of redox equilibria involving equalibrium pallasite assemblages are in good agreement with the experimental results and provide a lower limit to pallasite redox stability; others involving disequilibrium assemblages, suggest that pallasites experienced localized, late-stage oxidation and reduction effects. Consideration of the redox buffer metal-olivine-orthopyroxene utilizing calculated Eucrite Parent Body (EPB) mantle phase compositions indicates that small redox gradients may have existed in the EPB. Such gradients may have produced strong compositional variation within the EPB. In addition, there is apparently significant redox heterogeneity in the source area of Eagle Station Trio pallasites and Bocaiuva iron meteorites.

Righter, Kevin↗
NASA NTRS1988

Circumstellar material in meteorites - Noble gases, carbon and nitrogen

In addition to preserving a record of isotopically distinct reservoirs in the early solar system, some primitive meteorites contain discrete grains of presolar origin. Such grains are distinguished by the isotopically anomalous noble-gas components they contain. One such component consists of monoisotopic Ne-22, produced by decay of radioactive Na-22 with a 2.6 yr half-life. Two xenon components have also been identified: one synthesized apparently in a supernova, the other probably in a red giant star. Most of the grains that carry these noble-gas components are carbonaceous and contain isotopically anomalous C, N, or both. They include diamond and silicon carbide. Two unidentified carriers of isotopically anomalous nitrogen, unaccompanied by noble gases, occur in the brecciated stony iron meteorite, Bencubbin.

Anders, Edward↗
NASA NTRS1983

Development of a mass spectrometer system for the measurement of inert gases in meteorites

The study of the inert gases in meteorites has provided many clues as to the origin and evolution of the solar system. Particularly crucial and complex are the gases krypton and xenon. To accurately measure the isotopic compositions of these gases requires a mass spectrometer of high sensitivity and resolution. A previously unused and largely untested mass spectrometer system was brought to the point where it was ready for routine sample analyses. This involved, among other things, focusing the ion beam for optimal peak shape and sensitivity, documenting the instrument's response to a series of characteristic tests such as multplier gain checks, and interfacing the instrument to a computer to run the sample analyses. Following this testing and setting up, three iron meteorite samples were to be analyzed for argon, krypton, and xenon. The three samples were shown in prior work to possibly contain primordial heavy inert gases. Although these analyses have not yet been carried out, it is anticipated that they will be completed in the near future.

Palma, R. L.↗
NASA NTRS1996

Meteoritic Sulfur Isotopic Analysis

Funds were requested to continue our program in meteoritic sulfur isotopic analysis. We have recently detected a potential nucleosynthetic sulfur isotopic anomaly. We will search for potential carriers. The documentation of bulk systematics and the possible relation to nebular chemistry and oxygen isotopes will be explored. Analytical techniques for delta(sup 33), delta(sup 34)S, delta(sup 36)S isotopic analysis were improved. Analysis of sub milligram samples is now possible. A possible relation between sulfur isotopes and oxygen was detected, with similar group systematics noted, particularly in the case of aubrites, ureilites and entstatite chondrites. A possible nucleosynthetic excess S-33 has been noted in bulk ureilites and an oldhamite separate from Norton County. High energy proton (approximately 1 GeV) bombardments of iron foils were done to experimentally determine S-33, S-36 spallogenic yields for quantitation of isotopic measurements in iron meteorites. Techniques for measurement of mineral separates were perfected and an analysis program initiated. The systematic behavior of bulk sulfur isotopes will continue to be explored.

Thiemens, Mark H.↗
NASA NTRS1993

Trace element distributions in primitive achondrites

The primitive achondrites have approximately chondritic bulk chemical composition but achondritic textures. Clayton et al. show that nine of these meteorites, the acapulcoites and the lodranites, have similar oxygen isotopic compositions. The acapulcoites appear to be highly metamorphosed, but undifferentiated meteorites of chondritic composition; whereas, the lodranites appear to have lost a feldspathic partial melt. In order to learn more about metamorphic processes and partial melt removal, we have measured the trace element compositions of constituent phases of a number of primitive achondrites by ion microprobe. We have analyzed two acapulcoites, Acapulco and ALH81261 (paired with ALH77081), and three londranites, Lodran, LEW88280, and MAC88177. In addition, we analyzed LEW88663, which has the bulk composition, mineral chemistry, and oxygen isotopic composition of L-chondrites, but is metal-free and has an achondrite texture; and Divnoe, a plagioclase-poor, olivine-rich primitive achondrite with an oxygen isotopic composition similar to that of the group IAB iron meteorites. These meteorites show a variety of REE patterns in their constituent phases, and there are consistent differences between acapulcoites and lodranites that are consistent with removal of a LREE- and Eu-enriched melt that is apparently responsible for the low plagioclase content of lodranites.

Davis, Andrew M.↗
NASA NTRS1976

A source mechanism for meteorites controlled by the Yarkovsky effect

Some previous difficulties associated with attributing an asteroid-belt origin to meteorites are briefly reviewed. To overcome these, a two-step mechanism is proposed by which small fragments produced by asteroid collisions are gradually sent into eccentric earth-crossing orbits, while the larger parent bodies themselves remain relatively unaffected. Central to this mechanism is the Yarkovsky effect, which arises from the asymmetric reradiation emitted by an illuminated rotating body. Not only can the Yarkovsky effect be three orders of magnitude greater than the Poynting-Robertson drag, but the Yarkovsky acceleration can also be either positive or negative, depending on the sense of the body's rotation. The second stage of the proposed mechanism becomes important only when either secular acceleration causes the orbital elements of the body to evolve into a secular resonance with Jupiter. The Yarkovsky acceleration is explicitly calculated for both cylindrical and spherical bodies. When the orbital consequences of this acceleration acting alone on small asteroid-belt fragments are determined, the results are found to be reasonably consistent with both the relative and absolute cosmic-ray exposure ages of stony and iron meteorites.

Peterson, C.↗
DOE OSTI2021

Improving ChemCam LIBS long-distance elemental compositions using empirical abundance trends

The ChemCam instrument on the Curiosity rover provides chemical compositions of Martian rocks and soils using remote laser-induced breakdown spectroscopy (LIBS). The elemental calibration is stable as a function of distance for Ti, Fe, Mg, and Ca. The calibration shows small, systematically increasing abundance trends as a function of distance for Al, Na, K, and to some extent, Si. The distance effect is known to be due to a dependence with distance on the relative strengths of atomic transition lines. Emission lines representing transitions from relatively low energy levels remain intense at longer distances while emission lines representing transitions from higher energy levels decrease in intensity more rapidly as a function of distance. The multivariate algorithms used to determine elemental compositions rely on a large number of emission lines in many cases, so rather than trying to correct all emission lines, a study was made of the predicted compositions as a function of distance, in order to determine an empirical correction. Abundance trends can be well approximated by a linear trend with distance within the ranges of abundances and distances observed up to ~6 m. Data from 11 distinct geological members and data groups of the Murray formation in Gale crater, Mars, were used to form the model, selecting the members and data groups yielding the best statistics. The model was tested using data from several targets observed from two different distances, and using data from the Kimberley formation, the composition of which is significantly different from the Murray formation, showing that the model works on other compositions beyond those used to build the model. For long-distance observations up to ~6 m, corrections can be made back to an equivalent composition at the median distance of ChemCam observations (2.6 m). Finally, the model has been validated up to 6.2 m, although ChemCam is able to observe bedrock targets to >7 m, and iron meteorites to distances of >9 m.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Density of Fe-Ni-C Liquids at High Pressures and Implications for Liquid Cores of Earth and the Moon

The presence of light elements in the metallic cores of the Earth, the Moon, and other rocky planetary bodies has been widely proposed. Carbon is among the top candidates in light of its high cosmic abundance, siderophile nature, and ubiquity in iron meteorites. It is, however, still controversial whether carbon-rich core compositional models can account for the seismic velocity observations within the Earth and lunar cores. In this paper we report the density and elasticity of Fe 90 Ni 10 -3 wt.% C and Fe 90 Ni 10 -5 wt.% C liquid alloys using synchrotron-based X-ray absorption experiments and first-principles molecular dynamics simulations. Our results show that alloying of 3 wt.% and 5 wt.% C lowers the density of Fe 90 Ni 10 liquid by ~2.9-3.1% at 2 GPa, and ~3.4-3.6% at 9 GPa. More intriguingly, our experiments and simulations both demonstrate that the bulk moduli of the Fe-Ni-C liquids are similar to or slightly higher than those of Fe-Ni liquids. Thus, the calculated compressional velocity ($v_p$) of Fe-Ni-C liquids are higher than that of pure Fe-Ni alloy, promoting carbon as a possible candidate to explain the elevated v p in the Earth's outer core. However, the values and slopes of both density and v p of the studied two Fe-Ni-C liquids do not match the outer core seismic models, suggesting that carbon may not be the sole principal light element in Earth's outer core. The high $v_p$ of Fe-Ni-C liquids does not match the presumptive $v_p$ of the lunar outer core well, indicating that carbon is less likely to be its dominant light element.

58 GEOSCIENCES↗
DOE OSTI2023

Hardware, methodology and applications of 2 + D backscatter Mössbauer spectroscopy with simultaneous x-ray and γ-ray detection

Abstract A unique method is presented for the acquisition and analysis of 57 Fe backscatter Mössbauer spectra with simultaneous detection of the resonant 14.4 keV γ -rays and the characteristic 6.4 keV x-rays, using a custom-built multi-parameter analyser constructed on the basis of commercial analogue to digital converters and high-speed digital latches. The system allows for the simultaneous registration of Doppler-modulation velocities and photon energies, with up to 4096 and 8192 digital channels respectively. This arrangement is in contrast to most related systems, which detect at a single narrow energy window per detector. Samples of arbitrary atomic structure, morphology and surface topography can be studied without altering the setup or the analysis procedure, provided that the samples are at least micrometre sized. The hardware and software that are used to acquire data with minimal dead time are described and the custom and self-contained methods for post-measurement energy discrimination, background correction and velocity-axis folding are discussed. The data are fit using a general Hamiltonian model for the nuclear energy levels of 57 Fe and a quantum mechanical description of the angular momentum coupling is utilised, with consideration of the crystalline and chemical disorder of the sample under examination. Three examples of distinct magnetic systems, with thicknesses ranging from 5 μ m to 6 mm, that were studied using this method are presented, these are: an amorphous CoFeB-based ribbon with ultra-soft coercivity for high-frequency applications, magnetically hard Nd-Fe-B thick films on Si substrates, examined in both as-deposited and annealed states, and a sample from the nickel-rich iron meteorite NWA 6259 that contains the atomically ordered, elevated coercivity, L 1 0 phase of FeNi, tetrataenite. The wide applicability and usefulness of this method is thus demonstrated on three distinct sample morphologies that required little to no surface preparation prior to examination.

Engineering↗
NASA NTRS1968

Achievements in planetology, 1967

Planetology, terrestrial geochemistry and geophysics, impact cratering and metamorphism, lunar probes, stony-iron meteorites, and tektites - literature review for 1967

Source record↗
NASA NTRS1972

Shock melting and vaporization of lunar rocks and minerals.

The entropy associated with the thermodynamic states produced by hypervelocity meteoroid impacts at various velocities are calculated for a series of lunar rocks and minerals and compared with the entropy values required for melting and vaporization. Taking into account shock-induced phase changes in the silicates, we calculate that iron meteorites impacting at speeds varying from 4 to 6 km/sec will produce shock melting in quartz, plagioclase, olivine, and pyroxene. Although calculated with less certainty, impact speeds required for incipient vaporization vary from 7 to 11 km/sec for the range of minerals going from quartz to periclase for aluminum (silicate-like) projectiles. The impact velocities, which are required to induce melting in a soil, are calculated to be in the range of 3 to 4 km/sec, provided thermal equilibrium is achieved in the shock state.

Ahrens, T. J.↗
NASA NTRS1973

Shock history of mesosiderites.

The (still largely incomplete) shock histories of 18 stony-iron meteorites (classified as mesosiderites) are studied. The crystallographic character of kamacite in each (polished and etched) sample was determined by a back-reflection X-ray diffraction technique. All specimens were studied metallographically, and some by reflected light microscopy. The shock history of each sample is determined in kbar.

Jain, A. V.↗
NASA NTRS1973

He, Ne and Ar in chondritic Ni-Fe as irradiation hardness sensors.

Noble gas analyses of the Ni-Fe of 9 L, 5 H, and 2 LL chondrites quantitatively support previous suggestions of radiogenic He-4 recoil and He-3 deficits. Furthermore, noble gases in the Ni-Fe show evidence for in situ produced radiogenic He-4 and in some cases for recoil loss of Ar-38 and gain of Ne-21. The ratio of spallogenic Ar-38 and Ne-21 in the metal phase is found to correlate strongly with He-3/Ne-21 and Ne-22/Ne-21 in bulk samples of these chondrites. This is proof of the dependence of these ratios on the irradiation hardness experienced by the meteoroid in space. 'Hardness indices' n equals 1.9-2.2 are found, indicating that on the average the stone meteoroids from which the samples came were smaller in mass than iron meteoroids. The spallogenic Ne-21/Ar-38 ratio in metallic Ni-Fe can be used with the semi-empirical production model deduced from the Grant iron meteorite to calibrate spallogenic He-3/Ne-21 and Ne-21/Ar-38 in bulk samples of L, LL and H chondrites for meteoroid size and sample location allowing the estimation of minimal meteoroid masses.

Nyquist, L.↗
NASA NTRS1973

The physical nature of interplanetary dust as inferred by particles collected at 35 km

Particles were collected at an altitude of 35 km by two flights of a volume sampling micrometeorite collector. The collection scheme is very sensitive and is capable of collecting a significant number of particles. Many of the particles collected have chemical compositions similar to solar or to iron meteorites. Morphology of collected particles indicates that both true micrometeorites and ablation products were collected.

Brownlee, D. E.↗
NASA NTRS1973

Optical properties of carbonaceous chondrites and their relationship to asteroids

Results of diffuse reflectance measurements of nine samples of carbonaceous chondrites (one C1, three C2, four C3, and one C4) and one iron meteorite, Odessa. Measurements were also made of mineral mixtures in an attempt to understand the cause of some features of the meteorite reflectances. The C1 and C2 carbonaceous chondrites have reflectances low enough to match the anomalously low albedos of some asteroids. Some asteroids have spectral reflectances similar to carbonaceous chondrites, whereas others with flat or F-type curves appear to match simulated mineral mixtures with slightly greater amounts of the carbonaceous component than those found in the meteorites. This observation suggests either that surface physical processes such as melting may be enhancing the optical effect of opaque carbonaceous material on some asteroid surfaces and/or that these asteroids contain even more carbonaceous material than the C1 meteorites.

Johnson, T. V.↗