Presolar grains in meteorites

Nittler, L. R. (2003) Presolar stardust in meteorites recent advances and scientific frontiers. Earth and Planetary Science Letters, 209, 259-273. A good accessible review of presolar grains in meteorites. 

The discovery of presolar grains in meteorites has, for the first time, enabled the precise chemical and isotopic analysis of interstellar material (e.g., Anders and Zinner, 1993 Chapter 1.02). The huge variations in the isotopic compositions of all the elements analyzed in presolar grains is in stark contrast to the basically uniform isotopic composition of solar system materials (see Figure 1). This uniformity would have required an effective isotopic homogenization of all the material in the solar nebula, i.e., gas and dust, during the early stages of the formation of the solar system. 

Ott U. (2001) Presolar grains in meteorites an overview and some implications. Planet. Space Sci. 49, 763-767. 

A solar system origin could explain the anomalously high abundance of nanodiamonds relative to other types of presolar grains in meteorites (Hoppe and Zinner, 2000). The recent detection by the Infrared Space Observatory (ISO) of nanodiamonds formed in situ within the accretion disks of young stars confirms that nanodiamonds could indeed have formed in the inner solar system (Van Kerckhoven et al., 2002). 

Ott U (2002) Noble gases in meteorites— trapped components. Rev Mineral Geochem 47 71-100 Ott U, Begemaim F (2000) Spallation recoil and age of presolar grains in meteorites. Meteoritics Planet Sci 35 53-63... 

Zitmer E (1997) Presolar material in meteorites an overview. In Astrophysical Implications of the I aboratory Study of Presolar Materials. Bematowicz TJ and Zinner E (eds) AIP, New York, p 3-26 Zinner EK, Gopel C (2002) Aluminium-26 in H4 chondrites implications for its production and its usefulness as a fine-scale chronometer for early solar system events. Meteorit Planet Sci 37 1001-1013 Zinner E, Amari S, Guitmess R, Nguyen A, Stadermann FJ, Walker RM, I wis RS (2003) Presolar spinel grains from the Murray and Murchison carbonaceous chondrites. Geochim Cosmochim Acta 67 5083-5095... 

As noted previously, most of the presolar grains so far identified are circumstellar condensates (stardust), but some grains formed in interstellar space. The interstellar grains are not likely to contain large isotopic anomalies. So how can we recognize these interstellar grains in meteorites ... 

Zinner, E. (2004) Presolar grains. In Treatise on Geochemistry, Volume 1 Meteorites, Comets, and Planets, ed. Davis, A. M. Oxford Elsevier, pp. 17-39. A recent review of the state of knowledge about presolar grains. The on-line version is updated periodically. 

Bematowicz, T. J., Croat, T. K. and Daulton, T. L. (2006) Origin and evolution of carbonaceous presolar grains in stellar environments. In Meteorites and the Early Solar System II, eds. Lauretta, D. S. and McSween, H.Y., Jr. Tucson University of Arizona Press, pp. 109-126. 

As with the electron microprobe, the chemical composition is determined through comparison with standards. Corrections for interactions with different elements are also necessary. However, the standardization and correction procedures for the AES are much less mature than those for the electron probe. In cosmochemistry, the auger nanoprobe is used primarily to determine the chemical compositions of presolar grains. It is ideal for this application because it is a surface technique and has the same spatial resolution as the NanoSIMS (see below), which is used to identify presolar grains in situ in meteorite samples and IDPs. 

Nittler, L. R. (1997) Pre solar oxide grains in meteorites. In Astrophysical Implications of the Laboratory Study of Presolar Materials, T. J. Bematowicz E. K. Zinner, Eds., pp. 59-84. AIP Conf. Proc. 402. 

Stars form in dense cores within giant molecular clouds (see Fig. 1.4, Alves et al. 2001). About 1 % of their mass is in dust grains, produced in the final phases of stellar evolution. Molecular clouds are complex entities with extreme density variations, whose nature and scales are defined by turbulence. These transient environments provide dynamic reservoirs that thoroughly mix dust grains of diverse origins and composition before the violent star-formation process passes them on to young stars and planets. Remnants of this primitive dust from the Solar System formation exist as presolar grains in primitive chondritic meteorites and IDPs. 

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