Lead isotopic evidence for an old and rapid lunar magma ocean

The Moon’s early history remains enigmatic, with intensive debate over the timing and duration of the lunar magma ocean (LMO) and its consequences on the early thermal and chemical evolution of the Moon. Here, we report a lead-lead isochron age of 4406.1 ± 3.2 million years ago (Ma) with an extraordinarily high initial lead (Pb) composition (HIP) for a lunar meteorite Northwest Africa 14729. The HIP at ~4406 Ma implies Pb isotopic evolution from an early-formed, high-μ ( 238 U/ 204 Pb > 5000) reservoir that is genetically linked to the last remaining liquid of the LMO called urKREEP. This requires that lunar primordial differentiation was completed within approximately 150 million years (Myr) after the Solar System’s formation.