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Constraining the Source Craters of Apollo Impact Melts.

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Title: Constraining the Source Craters of Apollo Impact Melts.
Authors: Blevins, A. M.1 (AUTHOR) blevins2@purdue.edu, Minton, D. A.1 (AUTHOR), Huang, Y. H.2 (AUTHOR), Du, J.1 (AUTHOR), Tremblay, M. M.1 (AUTHOR), Fassett, C. I.3 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Aug2025, Vol. 130 Issue 8, p1-28. 28p.
Subject Terms: Lunar craters, Impact craters, Observations of the Moon, Moon, Meteorite craters, Bayesian analysis
Company/Entity: Apollo program (U.S.)
Abstract: Interpreting the age distribution of Apollo samples to determine the early bombardment history of the Moon has been fraught with controversy, and the question of how much material from large impact basins such as Imbrium is present in the Apollo sample collection remains unresolved. Here, we model impact melt production and transportation over lunar history to estimate the amount of melt that each basin should have contributed to the Apollo 14–17 sites. Our model results suggest that Imbrium contributes significantly to all four studied Apollo sites, but also that each site should contain more impact melt from basins older than Imbrium compared to what has been interpreted in the Apollo sample collection. We then use Bayesian inference to evaluate possible correlation between specific basins and groups of Apollo impact melt samples. We find that in every simulation, there are only a few basins sampled, but the specific basins (other than Imbrium) are different for each simulation. This suggests that most basins were not sampled in the suite of Apollo impact melts. Using a combination of numerical models and Bayesian statistics, we define four possible scenarios for the timing of basin emplacement. The impact flux for these scenarios varies from a smooth decline to a terminal "cataclysm." The behavior of impacts in the time before Imbrium remains unconstrained, and specific samples are needed to better understand this period in lunar history. Plain Language Summary: Many samples collected on the Moon during the Apollo missions that are associated with impact craters have been found to be roughly 3.9 billion years old. In the decades since the Apollo missions, the source craters of these samples have been debated. Imbrium (D = 1,321 km) is the largest crater on the nearside, and one of the youngest large craters (D> $D\hspace*{.5em} > $ 200 km) on the Moon. The majority of the 3.9 billion year old Apollo samples are believed to come from this crater. We used an impact bombardment model to simulate the lunar impact history and tracked material found at the Apollo 14–17 landing sites. Imbrium affected a significant portion of material at each of those sites, along with other large impact craters known as basins. There were many basin‐forming impacts the Moon prior to Imbrium, but only a few of them were sampled by the Apollo missions. This means most basins remain unsampled, and their age remains unknown. We also used statistical analyses to investigate which basins other than Imbrium could have been sampled by Apollo astronauts and when the impacts could have happened. We construct four possible scenarios for the timing of impacts on the Moon. Key Points: We modeled formation of both large basins and small, local craters by impact bombardment of the MoonWe identify four possible scenarios for the timing of basin formation based on numerical modeling and Bayesian inferenceMost lunar basins are not expected to contribute to the Apollo impact melt suite [ABSTRACT FROM AUTHOR]
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Abstract:Interpreting the age distribution of Apollo samples to determine the early bombardment history of the Moon has been fraught with controversy, and the question of how much material from large impact basins such as Imbrium is present in the Apollo sample collection remains unresolved. Here, we model impact melt production and transportation over lunar history to estimate the amount of melt that each basin should have contributed to the Apollo 14–17 sites. Our model results suggest that Imbrium contributes significantly to all four studied Apollo sites, but also that each site should contain more impact melt from basins older than Imbrium compared to what has been interpreted in the Apollo sample collection. We then use Bayesian inference to evaluate possible correlation between specific basins and groups of Apollo impact melt samples. We find that in every simulation, there are only a few basins sampled, but the specific basins (other than Imbrium) are different for each simulation. This suggests that most basins were not sampled in the suite of Apollo impact melts. Using a combination of numerical models and Bayesian statistics, we define four possible scenarios for the timing of basin emplacement. The impact flux for these scenarios varies from a smooth decline to a terminal "cataclysm." The behavior of impacts in the time before Imbrium remains unconstrained, and specific samples are needed to better understand this period in lunar history. Plain Language Summary: Many samples collected on the Moon during the Apollo missions that are associated with impact craters have been found to be roughly 3.9 billion years old. In the decades since the Apollo missions, the source craters of these samples have been debated. Imbrium (D = 1,321 km) is the largest crater on the nearside, and one of the youngest large craters (D> $D\hspace*{.5em} > $ 200 km) on the Moon. The majority of the 3.9 billion year old Apollo samples are believed to come from this crater. We used an impact bombardment model to simulate the lunar impact history and tracked material found at the Apollo 14–17 landing sites. Imbrium affected a significant portion of material at each of those sites, along with other large impact craters known as basins. There were many basin‐forming impacts the Moon prior to Imbrium, but only a few of them were sampled by the Apollo missions. This means most basins remain unsampled, and their age remains unknown. We also used statistical analyses to investigate which basins other than Imbrium could have been sampled by Apollo astronauts and when the impacts could have happened. We construct four possible scenarios for the timing of impacts on the Moon. Key Points: We modeled formation of both large basins and small, local craters by impact bombardment of the MoonWe identify four possible scenarios for the timing of basin formation based on numerical modeling and Bayesian inferenceMost lunar basins are not expected to contribute to the Apollo impact melt suite [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009137