Proposed Lunar Measurements of r-Process Radioisotopes to Distinguish the Origin of Deep-sea 244Pu

Abstract

Abstract 244Pu has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two 60Fe pulses from nearby supernovae. 244Pu is among the heaviest r-process products, and we consider whether it was created in supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded the nearby interstellar medium with 244Pu that was subsequently swept up by the supernova debris. We discuss how these possibilities can be probed by measuring 244Pu and other r-process radioisotopes such as 129I and 182Hf, both in lunar regolith samples returned to Earth by missions such as Chang’e and Artemis, and in deep-sea deposits.