Supernova-Produced 53Mn on Earth

For the time period from 1.5 to 4 Myr before the present we found in deep ocean ferromanganese crusts a Mn-53 excess concentration in terms of Mn-53/Mn of about 4 x 10(-14) over that expected for cosmogenic production. We conclude that this Mn-53 is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where Fe-60 has been found earlier. This overabundance confirms the supernova origin of that Fe-60. For the first time, supernova-formed Mn-53 has been detected and it is the second positively identified radioisotope from the same supernova. The ratio Mn-53/Fe-60 of about 14 is consistent with that expected for a SN with a 11-25 M-circle dot progenitor mass and solar metallicity.