Individual Presolar Grains Research Articles

Analyzing individual presolar grains with CHARISMA

Isotopic analysis of heavy elements in individual stardust grains is important in testing and constraining theories of stellar nucleosynthesis. These analyses are challenging in that the grains are very small, the largest being perhaps a few microns in diameter, and contain only trace concentrations of heavy elements, generally on the order of ppm. In addition, isotopic analysis requires the suppression of isobaric interferences. We describe a unique instrument, based on resonant ionization mass spectrometry, that has successfully characterized such grains for the past several years, and report on some recent upgrades that significantly enhance the instrumental capabilities. The fundamental principles and operational details are discussed, along with illustrative results and plans for future modifications.

Isotopic astronomy from anomalies in meteorites: recent advances and new frontiers

Considers the study of isotopically anomalous materials in meteorites which is a rapidly developing subdiscipline of astronomy providing primary data on stellar and supernova nucleosynthesis. Several types of presolar circumstellar grains have been analyzed and exhibit wide variations in isotopic signature, probably indicating many stellar sources. Refractory Ca-, Al-rich inclusions (CAIs) are thought to have formed within the solar system but surprisingly preserve a variety of anomaly signatures, one of which points towards a component originating in neutron-rich nuclear statistical equilibrium deep inside one or more supernovae. The uncertain cosmochemical mode of origin of the CAI anomalies, however, remains an important unsolved problem. Barium r-process anomalies provide critical insights because cosmochemically volatile holdups at 137Cs (T12/=30 a) and 135Cs (T12/=2.3 Ma) constrain, respectively, the time of Ba condensation relative to nucleosynthesis and the age of any 'exotic' Ba component at the time of CAI formation approximately 4566 Ma ago. An important frontier for future innovation is the development of mass analysis techniques for ultra-small trace element samples from individual presolar grains and micro-CAIs.