There is extensive geologic evidence of ancient volcanic activity on the Moon, but it is unclear how long that volcanism persisted. Magma fountains produce volcanic glasses, which have previously been found in samples of the Moon’s surface. Dr. Qiuli Li and colleagues from the Institute of Geology and Geophysics at the Chinese Academy of Sciences have analyzed around 3,000 glass beads from lunar soil samples collected by China’s Chang’e-5 mission. They’ve identified three glass beads as having a volcanic origin on the basis of their textures, chemical compositions, and sulfur isotopes. Uranium-lead dating of these volcanic beads shows that they formed approximately 123 million years ago.
Volcanic eruption producing glass beads on the Moon. Image credit: T. Zhang & Y. Wang.
Samples collected by the Apollo, Luna and Chang’e‑5 missions have previously shown there was widespread basaltic volcanism on the Moon extending from about 4.4 to 2 billion years ago.
The findings of the current study demonstrate that volcanism persisted much longer than was previously suspected, at least on smaller, more localized scale.
“Dating of lunar volcanic basalt samples returned to Earth by the Apollo and Luna missions or delivered to Earth as lunar meteorites has shown that lunar basaltic volcanism continued until at least 2.9-2.8 billion years ago,” the researchers said.
“However, analysis of lunar samples returned by the Chang’e-5 mission has demonstrated that basaltic volcanism persisted until at least 2 billion years ago.”
“Remote sensing observations have indicated potentially even younger volcanism during the late Copernican era (less than 800 million years ago) on the Moon.”
“However, none of these remote observations provide a precise date for the potential volcanism.”
“In addition, the proposed extrusions of late-Copernican mare basalt cover only restricted areas, no samples of which are available.”
“Eruptions of gas-rich magma can generate magma fountains, which produce submillimeter glass beads.”
“Such beads could potentially be deposited over wide areas and subsequently be transported further across the lunar surface by impact.”
“The volcanic glasses could be a trace component in existing samples.”
In their study, Dr. Li and co-authors sorted through 3,000 tiny glass beads they recovered from a lunar sample collected by Chang’e‑5, examining the bead’s chemical compositions, physical textures and sulfur isotopes to distinguish potential volcanic glasses from glasses produced by meteorite impacts.
They identified three beads as being of volcanic origin, then used radiometric dating to determine the beads formed 123 million years ago.
The volcanic beads contain high abundances of potassium, phosphorus and rare-earth elements, known as KREEP elements, which can produce radioactive heating.
Localized heating due to KREEP elements might melt rocks in the Moon’s mantle, leading to small amounts of magma erupting to the surface.
“We measured high abundances of rare earth elements and thorium in the volcanic glass beads, which could indicate that such recent volcanism was related to local enrichment of heat-generating elements in the mantle sources of the magma,” the researchers said.
Their paper appears in the journal Science.
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Bi-Wen Wang et al. 2024. Returned samples indicate volcanism on the Moon 120 million years ago. Science 385 (6713); doi: 1077-1080; doi: 10.1126/science.adk6635
Source : Breaking Science News