Extinct manganese-53 in carbonates from the Orgueil meteorite

The presence of the radionuclide 53Mn in the early Solar System is well established. Manganese-53 decays by e-capture (half-life 3.7 Ma) and can be detected as isotopic overabundances of its daughter 53Cr in meteorites. It is produced in Type II supernovae but not in AGB stars. Production by bombardment of Fe nuclei with energetic particles from the young Sun is a distinct possibility. The study of the Mn–Cr isotope system in meteorites has provided a wealth of useful information on early Solar System history. Evidence for the former presence of 53Mn has been found in a variety of Solar System objects, including carbonates. High spatial resolution ion microprobe analyses of individual carbonate grains from the Orgueil meteorite have shown linear correlations between 53Cr excesses and Mn/Cr ratios in individual grains, indicative of in situ decay of radioactive 53Mn. The well-defined isochrons have chronological significance, with absolute ages between 4561 and 4565 Ma. The carbonate data imply extensive aqueous activity on the Orgueil parent body over a period of several million years, starting ∼3 Ma after Solar System formation that most likely was the result of impact heating and latent heat from the decay of radioactive 26Al and 60Fe.