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

Pu-244 has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two Fe-60 pulses from nearby supernovae. Pu-244 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 Pu-244 that was subsequently swept up by the supernova debris. We discuss how these possibilities can be probed by measuring Pu-244 and other r-process radioisotopes such as I-129 and Hf-182, both in lunar regolith samples returned to Earth by missions such as Chang'e and Artemis, and in deep-sea deposits.

Automated summary

Pu-244 has been found in deep-sea deposits from the past 10 million years, including two Fe-60 pulses from nearby supernovae. The origin of Pu-244, one of the heaviest r-process products, is debated. It could have been created in supernovae, although nucleosynthesis simulations suggest otherwise, or in an earlier kilonova event that spread Pu-244 in the nearby interstellar medium, later swept up by supernova debris. To investigate these possibilities, measurements of Pu-244, I-129, and Hf-182 in lunar regolith samples and deep-sea deposits are suggested.