Youngest basaltic lunar meteorite fills nearly one billion-year gap in moon's volcanic history
A 2.35-billion-year-old meteorite with a unique chemical signature, found in Africa in 2023, plugs a major gap in our understanding of the moon's volcanic history.
Introduction
Presented at the Goldschmidt Conference in Prague, findings from analyses of the Northwest Africa 16286 meteorite offer fresh insights into how the moon's interior evolved, highlighting the long-lived nature of its volcanic activity.
Analyses by researchers from the University of Manchester, U.K., lend weight to a theory that the moon retained internal heat-generating processes that powered lunar volcanic activity in several distinct phases.
Unique Geological Characteristics
Lead isotope analysis dates the rock's formation to around 2.35 billion years ago, during a period from which few lunar samples exist, positioning it as the youngest basaltic lunar meteorite discovered on Earth. Its rare geochemical profile sets it apart from those returned by previous moon missions, with chemical evidence indicating it likely formed from a lava flow that solidified after emerging from deep within the moon.
Images of the sample obtained using a scanning electron microscope. Different shades of grey highlight different chemical compositions of the minerals making up the rock.
Research Insights
Dr. Joshua Snape, a Research Fellow at the University of Manchester, emphasized the significance of lunar meteorites. He stated, "Lunar rocks from sample return missions are fantastic in the insights they provide us, but they are limited to the immediate areas surrounding those mission landing sites."
“By contrast, lunar meteorites can potentially be ejected by impact cratering occurring anywhere on the moon's surface,” Dr. Snape added. “This particular rock provides new constraints about when and how volcanic activity occurred on the moon.”
Geological Implications
Containing relatively large crystals of mineral olivine, the rock is a type of lunar volcanic basalt known as olivine-phyric basalt. It contains moderate levels of titanium and high levels of potassium. The Pb isotope composition of the rock—a geochemical fingerprint retained from when the rock formed—points to it originating from a source in the moon's interior with an unusually high uranium-to-lead ratio.
Age and Composition
The significance of the meteorite extends to its age, which fills an almost billion-year gap in lunar volcanic history. Notably, it is younger than the basalts collected by the Apollo, Luna, and Chang'e 6 missions, yet older than the much younger rocks brought back by China's Chang'e 5 mission.
“Moon rocks are rare, so it's always interesting when we get something that stands out and looks different from everything else,” Dr. Snape noted, discussing the implications of the sample’s unique age and composition.
Future Directions
The researchers plan to publish their findings in full in a peer-reviewed journal later this year. These findings may guide future lunar explorations and help identify the mechanisms enabling ongoing internal heat generation on the moon.
Conclusion
This research marks a significant step forward in lunar geology, revealing new information about the moon's volcanic history and composition that will undoubtedly influence future studies and exploratory missions to the lunar surface.
