Presolar grains as probes of the early solar system

Presolar grains as probes of the early solar system 

Almost immediately after the discovery of presolar grains, it was clear that they could only be found in the most primitive chondrites, those that had suffered the least amount of thermal metamorphism. Further work showed that the abundances of presolar grains, when normalized to the content of fine-grained matrix where the grains reside, correlated strongly 

The characteristics of the presolar diamonds also change with the metamorphic grade of the host meteorite. F igure 5.15 shows the typical bimodal release of heavy noble gases (here illustrated by xenon) in Orgueil, an unheated chondrite. This pattern is compared to the xenon-release patterns of two ordinary chondrites that have experienced different degrees of mild metamorphism. The amount of low-temperature gas, labeled P3 for historical reasons, is a sensitive function of temperature. Its abundance correlates well with other indicators of 

Presolar grains are very difficult to study because of their small size. The technical requirements for studying presolar grains have led to the development of a new generation of analytical equipment that has made analysis of particles of a few tenths of a micron in diameter and larger feasible. Further improvements in analytical capability can be expected in the near future. We may even reach the point where the precision of our measurements is limited by the number of atoms present in a grain, a limit that cannot be overcome by any analytical technique. 

What are the important differences between circumstellar condensates and interstellar grains  

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