Solar nebula isotope anomalies

Loss RD, Lugmair GW, Davis AM, MacPherson GJ (1994) Isotopically distinct reservoirs in the solar nebula isotope anomalies in Vigarano meteorite inclusions. Astrophys J 436 L193-L196 Lugmair GW, Marti K (1977) Sm-Nd-Pu timepieces in the Angra dos Reis meteorite. Earth Planet Sci Lett 35 273-284... 

A few inclusions are exceptional in that they show isotopic anomalies for virtually every element studied, notably in the heavier isotopes of O, Mg, Si, Ca, Ti etc. these have been called FUN (fractionation and unknown nuclear) anomalies by Wasserburg and his colleagues and they may be due to unmodified stellar ejecta that were incorporated into the solar nebula in a solid form in which they survived. 

Overall, the origin of the oxygen isotopic anomalies in the Solar System is still a matter of debate (Thiemens 2006). After the failure of the supernova hypothesis (Clayton et al. 1973), these anomalies most likely originated through chemical or physical processes within the nebula. 

To the extent that this high precision, high accuracy result represents the absolute age of crystallization of CAls generally, it provides a measure of the age of formation of the solar system since several lines of evidence, in addition to the absolute Pb-Pb ages, indicate that CAls are the first sohd materials to have formed in the solar nebula (for a review, see Podosek and Swindle (1988)). In fact, it is the relative abundances of the short-lived radionuclides, especially A1, which provides the primary indication that CAls are indeed these first local materials. Other evidence is more circumstantial, e.g., the prevalence of large stable isotope anomalies in CAls compared to other material of solar system origin (see Chapter 1.08). We will return to the issue of antiquity of CAls when we examine the distribution of short-hved isotopes among different CAl types. 

The bulk SoS isotopic composition shows a high level of homogeneity. This is why it is mostly based on the terrestrial data. For H and the noble gases, as well as for Sr, Nd, Hf, Os, and Pb, some adjustments are required [30]. There are exceptions, however, to this high bulk isotopic homogeneity. One is due to the decay of relatively short-lived radionuclides that existed in the early SoS, and decayed in early formed solids in the solar nebula. Also interplanetary dust particles contain isotopic signatures apparently caused by chemical processes. Additional isotopic anomalies are observed in some meteoritic inclusions or grains (see Sect. 6.3). 

In addition to the above tools, we are developing other tools related to Galactic chemical evolution. These include a Nuclear Reactions Tool, a Nuclear Network Tool, and a Stellar Ejecta Tool. The Nuclear Reactions Tool will help users calculate nuclear reaction rates and help organize, view, and sort many of the common parameters need for these calculations. The Nuclear Network Tool will provide an easy way to evolve a system of species through time for a given environment s temperature and pressure. The features of the Stellar Ejecta Tool are designed to help a user understand the isotopic anomalies found in primitive meteorites or presolar grains. The Stellar Ejecta Tool will provide an easy way to view the isotopic abundance of a star s ejecta, run a nuclear decay network on this material, and then mix it with a second distribution of isotopic abundances. In this way it can simulate systems such as a late injection of material into the early solar nebula. When these tools are released, we will announce them over the Webnucleo mail list (see below). 

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