Molecular clouds isotopic anomalies

One implication of the discovery that all pre-existing solids were not vaporized and recondensed in the early solar system is the possibility that variations in the U/ U ratio could have been inherited from the Sun s parent molecular cloud. In addition, the short-lived nuclide Cm, which decays to U, might have been present. Recent studies have begun to re-investigate the assumption of constant U/ U in early solar system materials. A search for uranium isotopic anomalies in relatively large samples of a wide range of chondrites, achondrites, and terrestrial rocks found the U/ U ratio to be constant to... 

Carbonaceous material (Fig. 12.8b) is intimately mixed with silicates and is very abundant (carbon abundance averages 13% and varies up to 50%) in CP IDPs. Some carbon is elemental (graphite), but C-H stretching resonances in infrared spectra show that aliphatic hydrocarbons are also present. Polycyclic aromatic hydrocarbons (PAHs) also occur. Nanodiamonds have been identified in cluster IDPs, but not in smaller CP IDPs. Enormous D/H and 15N/14N anomalies have been measured in bulk IDPs, and the hydrogen isotopic anomalies are correlated with organic-rich domains. Ratios of D/H as high as 25 times the solar ratio suggest the presence of molecular cloud materials. 

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