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.
Iron meteorites with oxygen-bearing phases can be classified in terms of their oxygen isotopic abundances. These iron meteorite classes are isotopically similar to various stony meteorite classes, which may indicate a common origin. The group IAB and IIICD irons may be related to the winonaites; group IIE irons may be related to H chondrites; group IVA irons may be related to L or LL chondrites.
Iron meteorites analyzed in this study have nitrogen concentrations 70 microg/g or less and delta N-15 from -90 to +150 percent. Although the iron meteorites have a large range of delta N-15, most have values more negative than -50 percent. The nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies. The data do not suggest the existence of a well-mixed solar nebular reservoir for nitrogen, as was already inferred from data from stony meteorites. The range of greater than 1100 percent observed for delta N-15 in bulk meteorites is probably too large to be accounted for by physical and chemical mass-dependent fractionation processes in the solar nebula, and thus reflects nebular inhomogeneities of nucleosynthetic origin.
Iron meteorites contain the record of the galactic cosmic ray intensity over a 100 to 1000 Myr time scale. A method was developed to calculate the cosmic ray exposure ages of iron meteorites. Discrepanices between exposure ages are discussed.
Iron meteorites present a challenge for the I-Xe dating technique because it is usually the inclusions, not metal, that contain radiogenic xenon and iodine. Silicate inclusions are frequent in only types IAB and IIE, and earlier studies of irons have demonstrated that I-Xe system can survive intact in these inclusions preserving valuable age information. Our previous studies of the I-Xe record in pyroxene grains from Toluca iron suggested an intriguing relationship between apparent I-Xe ages and (Mg+Fe)/Fe ratios. The I-Xe system in K-feldspar inclusions from Colomera (IIE) had the fingerprint of slow cooling, with an indicated cooling rate of 2-4 C/Ma. Here we present studies of the iodine-xenon system in a silicate-graphite-metal (SiGrMet) inclusion of the IA Campo del Cielo iron meteorite from the collection of the Museum of Natural History in Vienna.
Iron meteorites genetic classification based on parent body cooling rate and Ga-Ge trace element content
Iron meteorites analysis for Ni, Co, P, C, S and Cu elements by milling technique, noting superiority degree based on Co-Ni correlation
Iron and stony iron meteorite cooling rates and thermal models, showing melting, radioactive heat source redistribution and surface heating effects
The chemical composition of the metal phase of iron meteorites is traced through an idealized traditional history from condensation, oxidation, and accretion in the nebula to melting, segregation, and freezing in a parent body, considering the following fifteen elements: Au, Co, Cu, Fe, Ga, Ge, Ir, Mo, Ni, Os, Pd, Pt, Re, Rh, and Ru. Twelve iron meteorite groups resolved by Scott and Wasson (1975) are considered in the framework of cosmochemical historical analysis. The parent bodies of five of these groups seem to have had a traditional history. The others seem to have had more unusual histories. For example, the composition of the metal in group IVB matches that predicted for the metal condensate at 1270 K, implying accretion at high temperatures; and the metal in group IVA has a composition indicative of aggregates undergoing progressive stages of partial melting.
Iron and iron-stony meteorites cooling rates in relation to Ni content and Widmanstatten structure suggest development in different thermal environments
Iron and stony meteorite cooling rates determined by measuring kamacite bandwidth, bulk nickel content and composition
Iron troilite meteorites lead isotopic, Pb and U concentrations, considering fractionation and terrestrial contamination effects
Iron and nickel-iron samples subjected to treatment by an arc-heated plasma of ionized air were used to model meteor ablation. The artificial ablation debris and fusion crusts were compared to the fusion crusts of three natural iron meteorities and to magnetic spherules from deep-sea manganese nodules. An outer discontinuous crust of magnetite and wuestite, followed by an unoxidized metallic zone, was observed in the artificially produced samples. Fractionation of less volatile elements was also noted.
Fe meteorites with high Ge content, tabulating concentrations of Ni, Ga, Ge and Ir
The tritium content of three stony meteorites and one iron meteorite
Vanadium concentrations in meteoritic irons and sulfide modules from iron meteorites determined by neutron activation
Carbon 14 content and terrestrial age of twelve stony meteorites and one iron meteorite
Resonance ionization mass spectrometry is used to determine the Re and Os abundances by isotope dilution (ID) and to measure Os-187/Os-186 ratios from 19 iron meteorites. Abundances range from 1.4 to 4800 ppb Re, and from 13 to 65,000 ppb Os, and generally agree well with previous ID and neutron activation results. The Re and Os data suggest that abundance trends in these iron groups may be entirely explained by fractional crystallization. Whole-rock isochrons for the IIAB and IIIAB groups are statistically indistinguishable. Pooled data yield an initial Os-187/Os-186 of 0.794 +/- 0.010 Ga. Given the errors in the slope and half life, this age does not differ significantly from the canonical chondrite age of 4.56 Ga, but could be as young as 4.46 Ga.