There is plenty of geological evidence that the Moon had ancient volcanic activity, but it is unclear how long that activity lasted. Magma eruptions create volcanic glass, which has been found in lunar samples before. Dr. Li Qiuli of the Institute of Geology and Geophysics, Chinese Academy of Sciences, and colleagues analyzed about 3,000 glass beads taken from lunar soil samples collected by China's Chang'e-5 mission. They identified three glass beads as being of volcanic origin based on their texture, chemical composition, and sulfur isotopes. Uranium-lead dating of these volcanic beads determined that they formed about 123 million years ago.
Samples collected by the Apollo, Luna and Chang'e-5 missions have so far shown that the Moon experienced widespread basaltic volcanic activity between about 4.4 billion and 2 billion years ago.
The findings suggest that, at least on small, localized scales, volcanic activity continued for much longer than previously thought.
“Dating of lunar volcanic basalt samples returned to Earth by the Apollo and Luna missions or delivered to Earth as lunar meteorites reveals that lunar basaltic volcanism continued at least 2.9 to 2.8 billion years ago,” the researchers said.
“However, analysis of lunar samples returned by the Chang'e-5 mission demonstrates that basaltic volcanism persisted at least 2 billion years ago.”
“Remote sensing observations suggest that there may have been more recent volcanic activity on the Moon during the Late Copernican epoch (less than 800 million years ago).”
“However, none of these remote sensing observations provide precise dates for possible volcanic activity.”
“Furthermore, the proposed Late Copernican Ocean basalt outbursts cover only a limited area, and no samples are available.”
“Eruptions of gas-rich magma can produce magma fountains that produce sub-millimeter glass beads.”
“These beads could be deposited over a wide area and then transported farther across the lunar surface by impacts.”
“Volcanic glass may be a trace component in existing samples.”
In their study, Dr Li and his co-authors sorted 3,000 tiny glass beads retrieved from lunar samples collected by Chang'e-5, examining the beads' chemical composition, physical texture, and sulfur isotopes to distinguish between volcanic glass and glass produced by meteorite impacts.
They identified three of the beads as being of volcanic origin and used radiometric dating to determine that the beads were formed 123 million years ago.
Volcanic beads are rich in potassium, phosphorus, and rare earth elements, known as KREEP elements, which can produce radioactive heat.
Localized heating by KREEP elements could melt rocks in the Moon's mantle, causing small amounts of magma to erupt to the surface.
“The volcanic glass beads contained large amounts of rare earth elements and thorium, which may indicate that recent volcanic activity is associated with local enrichment of heat-producing elements in the mantle source of magma,” the researchers said.
Their paper Published in a journal Science.
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Wang Biwen others2024. Samples brought back indicate volcanic activity on the moon 120 million years ago. Science 385 (6713); doi: 1077-1080; doi: 10.1126/science.adk6635
Source: www.sci.news
