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

TL;DR

This paper explores how lunar and deep-sea measurements of $r$-process radioisotopes like $^{244}$Pu can reveal their astrophysical origins, distinguishing between supernovae and kilonova sources over the past 10 million years.

Contribution

It proposes a novel approach using lunar and deep-sea samples to identify the astrophysical sources of $r$-process isotopes, addressing current uncertainties in nucleosynthesis origins.

Findings

Potential to differentiate supernova and kilonova origins of $^{244}$Pu.

Feasibility of using lunar regolith and deep-sea deposits for isotope measurements.

Implications for understanding heavy element formation in the universe.

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 the supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded 244Pu in the nearby interstellar medium 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.