EVIDENCE FOR MAGNESIUM ISOTOPE HETEROGENEITY IN THE SOLAR PROTOPLANETARY DISK

With a half-life of 0.73 Myr, the 26Al-to-26Mg decay system is the most widely used short-lived chronometer for understanding the formation and earliest evolution of the solar protoplanetary disk. However, the validity of 26Al–26Mg ages of meteorites and their components relies on the critical assumption that the canonical 26Al/27Al ratio of ∼5 × 10−5 recorded by the oldest dated solids, calcium–aluminium-rich inclusions (CAIs), represents the initial abundance of 26Al for the solar system as a whole. Here, we report high-precision Mg-isotope measurements of inner solar system solids, asteroids, and planets demonstrating the existence of widespread heterogeneity in the mass-independent 26Mg composition (μ26Mg*) of bulk solar system reservoirs with solar or near-solar Al/M