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MS: Fachverband Massenspektrometrie

MS 7: Accelerator Mass Spectrometry

MS 7.5: Talk

Thursday, March 5, 2026, 15:45–16:00, N 6

Constraints on the local fluence of interstellar ⁶⁰Fe on the Moon — •Sebastian Zwickel^1,2, Sebastian Fichter¹, Michael Hotchkis³, Dominik Koll^1,4, Johannes Lachner¹, Marc Norman⁴, Stefan Pavetich⁴, Georg Rugel¹, Konstanze Stübner¹, Stephen Tims⁴, and Anton Wallner^1,2,4 — ¹HZDR, Dresden, Germany — ²TU Dresden, Germany — ³ANSTO, Sydney, Australia — ⁴ANU, Canberra, Australia

The lunar regolith is a promising archive for live interstellar radionuclides such as supernova-⁶⁰Fe and r-process ²⁴⁴Pu. Due to the absence of geological activity, interstellar material can accumulate in the upper regolith over a few to up to several hundred Myr. This provides an integral record of nucleosynthesis in the solar neighbourhood, albeit with limited time resolution. Our measurements of the interstellar particle influx probe the astrophysical site of the r-process using ²⁴⁴Pu and constrain the local lunar fluence of interstellar ⁶⁰Fe. Regolith mixing from continuous (micro-)meteoritic bombardment dilutes interstellar radionuclide inventories over depth and is taken into account.

This contribution presents new results on the local lunar fluence of interstellar ⁶⁰Fe obtained from surface soil samples. Lunar soils that are expected to contain the full ⁶⁰Fe inventory observed in previous lunar depth profiles and terrestrial archives were identified by relating cosmogenic ²⁶Al to interstellar ⁶⁰Fe. A lower limit of interstellar ⁶⁰Fe fluence was established from a sample with O(Myr) surface exposure. Together with ⁶⁰Fe, we also present first data on the search for interstellar ²⁴⁴Pu in lunar soil samples.

Keywords: r-Process; lunar; 60Fe; AMS; supernova