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Kelly, W. R.

Publications and source records attributed to Kelly, W. R..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Isotopically anomalous silver in the Santa Clara and Pinon iron meteorites

The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Pinon iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of Ag-107 relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1.4 x 10 to the 11th atoms of Ag-109/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of Ag-107/Ag-109 were found which are enriched in Ag-107 by 60 percent to 160 percent. The existence of an excess Ag-107 in these two meteorites, which have high Pd-108/Ag-109 ratios of about 7 x 10 to the 4th is established.

Kaiser, T.↗
NASA NTRS1978

Evidence for the existence of Pd-107 in the early solar system

Measurements of the concentration and isotopic composition of Ag and Pd in the Santa Clara iron meteorite suggest that in situ decay of Pd-107 occurred in the meteorite or its parent body. The initial solar ratio of Pd-107/Pd-110 is estimated from the observed ratio of excess Ag-107/Pd-110, and the value of the Pd ratio is incompatible with an interval of approximately 100,000,000 years between the end of nucleosynthesis and the formation of planetary objects but is compatible with a later injection of material. The inferred existence of Pd-107 and Al-26 indicates that the late injection included freshly synthesized material of both intermediate and low atomic weight on a similar time scale. The significance of the Pd-107/Ag-107 chronometer is considered.

Kelly, W. R.↗
NASA NTRS1977

Chemical fractionations in meteorites. VIII - Iron meteorites and the cosmochemical history of the metal phase

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.

Kelly, W. R.↗
NASA NTRS1977

The origin of iron meteorites

The chemistry of iron meteorites is compared with predictions of the chemical fractionations that develop during the cosmic history of the metal phase, from condensation and accretion through melting, segregation, and freezing. Of the 12 resolved iron meteorite groups, three appear to have evolved in bodies which accreted at temperatures in excess of 1000 K. In several cases, the core-forming process seems to have ceased prematurely, just as the metal began to melt and flow (group IAB with its silicate inclusions) or after the metal aggregated into pods but before it sank to form a core (group IVA, with groups IIAB and IIIAB being in more advanced stages). The Shaw chondrite contains residual metal from a partial melting process, as required to complement the fractional melts which refroze prematurely in the case of group IAB meteorites.

Kelly, W. R.↗