Evidence for an Early Formation of Serenitatis Basin at 4.25 Ga Shifts Lunar Chronology

Abstract Troctolite sample 76535, collected in Serenitatis basin during Apollo 17, formed at least 50 km deep, experienced maximum shock pressures of 6 GPa, and has a 40 Ar/ 39 Ar excavation age of 4.25 Ga. Previous work attributed 76535 to the South Pole‐Aitken (SPA) basin, presumably dating the SPA‐impact and constraining lunar bombardment history. Here we use the iSALE‐2D shock‐physics code and gravity inversion modeling to determine if instead the Serenitatis impact event excavated 76535. We find nearly 140,000 km 3 of material (∼2% of near‐surface ejecta) matching the depth and pressure constraints of 76535 is displaced to the surface during crater collapse of a Serenitatis‐like impact event. We conclude that the Serenitatis impact event possibly excavated 76535, redefining its age to 4.25 Ga, 300 My older than the consensus age based on Apollo 17 samples. This finding would provide an important anchor point where lunar chronology where bombardment flux is especially uncertain.

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Publication Details

Journal
Geophysical Research Letters
Published
2025-09-18
DOI
https://doi.org/10.1029/2025gl116654
Primary Topic
Planetary Science and Exploration
Type
article
Field-Weighted Citation Impact
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article

Evidence for an Early Formation of Serenitatis Basin at 4.25 Ga Shifts Lunar Chronology

Adrien Broquet, Brandon Johnson, J. C. Andrews‐Hanna, Evan Bjonnes et al.
Geophysical Research Letters
Planetary Science and Exploration
article

Evidence for an Early Formation of Serenitatis Basin at 4.25 Ga Shifts Lunar Chronology

Adrien Broquet, Brandon Johnson, J. C. Andrews‐Hanna, Evan Bjonnes, W. S. Kiefer, Shigeru Wakita, I. Garrick‐Bethell
article en

Abstract

Abstract Troctolite sample 76535, collected in Serenitatis basin during Apollo 17, formed at least 50 km deep, experienced maximum shock pressures of 6 GPa, and has a 40 Ar/ 39 Ar excavation age of 4.25 Ga. Previous work attributed 76535 to the South Pole‐Aitken (SPA) basin, presumably dating the SPA‐impact and constraining lunar bombardment history. Here we use the iSALE‐2D shock‐physics code and gravity inversion modeling to determine if instead the Serenitatis impact event excavated 76535. We find nearly 140,000 km 3 of material (∼2% of near‐surface ejecta) matching the depth and pressure constraints of 76535 is displaced to the surface during crater collapse of a Serenitatis‐like impact event. We conclude that the Serenitatis impact event possibly excavated 76535, redefining its age to 4.25 Ga, 300 My older than the consensus age based on Apollo 17 samples. This finding would provide an important anchor point where lunar chronology where bombardment flux is especially uncertain.

Geophysical Research LettersVol. 52(18)
Lawrence Livermore National Laboratory (US), University of Arizona (US), University of California, Santa Cruz (US), Purdue University West Lafayette (US), Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (DE), Lunar and Planetary Institute (US), Massachusetts Institute of Technology (US)
U.S. Department of Energy, National Aeronautics and Space Administration, Nuclear Safety and Security Commission, National Astronomical Observatory of Japan, Solar System Exploration Research Virtual Institute, Lawrence Livermore National Laboratory
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Planetary Science and Exploration
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