Glass Beads Reveal Moon Volcanism 120M Years Ago

There were volcanic eruptions on the Moon as recently as 120 million years ago, according to a new analysis of a lunar sample collected by the Chang'e‑5 mission. 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 2.0 billion years ago. The new findings demonstrate that volcanism persisted much longer than was previously suspected, at least on smaller, more localized scale. Bi-Wen Wang, Qian W.L. Zhang and colleagues sorted through more than 3000 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 identify three beads as being of volcanic origin, then used radiometric dating to determine the volcanic beads formed 123 ± 15 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, the researchers suggest. In a related Perspective, Yuri Amelin and Qing-zhu Yin discuss the difficulties in distinguishing volcanic glasses from impact glasses.