The cosmochemistry of boron isotopes

Abstract

The boron elemental abundances and isotopic compositions in the universe and constituents (stars, interstellar medium and the Solar System material) within it have important implications for the astrophysical origins of this element. Astronomical observations and laboratory analysis have revealed that despite a significant difference in boron abundances among different objects, the 11B/10B ratio of 4 appears to be ubiquitous (within measurement uncertainties) across the Galaxy. Galactic Cosmic Ray (GCR) spallation, which yields 11B/10B = 2.5, cannot have been the sole source of B; another mechanism that favors the production of 11B over that of 10B must have operated over the Galactic timescale. However, how exactly the Galaxy, interstellar medium, and the Solar System acquired the 11B/10B ratio of 4 remains poorly understood.