Beads suggest more recent lunar volcanic activity

A collection of glass beads retrieved by China's Chang'e 5 lunar mission revealed that the moon might have been geologically active as recently as 123 million years ago.

Lunar samples obtained before the mission indicated that the moon's volcanic activities had ceased approximately 3 billion years ago, suggesting it had become a "dead planet." However, the basaltic rock fragments returned by Chang'e 5 suggest a more recent period of volcanic activity, dating back to just 2 billion years ago.

A new study has revealed that three volcanic glass beads, which are supposed to be the products of rapid cooling of volcanic magma, formed only about 123 million years ago and were subsequently transported to the Chang'e 5 landing site.

The lunar molten rocks enriched with volatiles experienced a decrease in pressure as they ascended. This caused the volatiles to escape as gases, forming a gas reservoir above the underground magma, according to a study published in the Science journal last week.

Then, a small amount of magma formed aerosol and suspended particles within the gas reservoir, which were finally ejected onto the lunar surface, creating small volcanic glass beads.

Researchers from the Institute of Geology and Geophysics under the Chinese Academy of Sciences examined approximately 3,000 glass beads in returned lunar soil samples. They identified three of the beads as having a volcanic origin on the basis of their textures, chemical compositions and sulfur isotopes.

Radiometric dating of the three volcanic glass beads has determined their ages and pointed to volcanism at that time, according to the study.

The team also identified high abundances of rare earth elements and thorium in these glass beads, indicating that such recent volcanism was related to the enrichment of heat-generating elements in the mantle sources of the magma.

These findings have sparked new questions in lunar research, including the origin of these youthful volcanic glass beads, and have led to speculation about the potential existence of even more recent lunar volcanic activities.

The Chang'e 5 probe, which returned to Earth on Dec 17, 2020, retrieved 1,731 grams of lunar samples, consisting primarily of rocks and soil from the lunar surface.

Through analysis of those lunar samples, significant strides have been made, yielding over 80 publications in scientific journals. Among the findings are the identification of the "youngest" basalt on the moon, the discovery of a new lunar mineral and a kind of mineral that harbors water molecules.

This year, China's Chang'e-6 mission achieved a historic first by collecting nearly 1,935.3 grams of lunar samples from the far side of the moon. This endeavor is also of unique scientific significance and expected to substantially advance people's understanding of the moon's evolutionary history.

Xinhua