Inferences on the evidence for radioactive ⁵³Mn in the early Solar System

Abstract

Several now-extinct radionuclides are believed to have been present in the early Solar System¹ and have been used to infer the time-scales for various processes during its formation. However, the precise interpretation of the Chronometric significance of an extinct nuclide depends on whether isotopic heterogeneities exist in that nuclide and/or in its daughter product. This is probable because such heterogeneities have already been found in many elements. Birck and Allègre² have recently reported data suggesting the presence of a new extinct nuclide, ⁵³Mn (mean life τ=5 Myr). In this letter I show that their data are inconsistent with the prediction of a single-stage model in which both Mn and its daughter element Cr were isotopically homogeneous. I also explore the virtues and consequences of the three alternative interpretations of the inconsistency: (1) the host material has experienced multiple-stage evolution, (2) ⁵³Mn was heterogeneously distributed, or (3) ⁵³Cr has intrinsic anomalies.