Supernovae and lunar melting

THE view that a supernova explosion preceded the formation of the Solar System¹ by at most a few million years has gained support from the interpretation of meteoritic isotope anomalies by Latimer et al.². We suggest here another significant piece of evidence for this viewpoint, not mentioned in their report - that supernova-produced²⁶ A1 (half life, 0.7 Myr) is also the only known physical heat source for melting of the lunar interior.