Returned lunar glass beads indicate moon still alive 120 million years ago

BEIJING, Sept. 9 (Xinhua) -- 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 120 million years ago.

Lunar samples obtained prior to 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 experience a decrease in pressure as they ascend. This causes the volatiles to escape as gases, forming a gas reservoir above the underground magma, according to a study published in the journal Science last week.

Then, a small amount of magma forms aerosol and suspended particles within the gas reservoir, which are finally ejected explosively onto the lunar surface to translate into small volcanic glass beads.

The researchers from the Institute of Geology and Geophysics under the Chinese Academy of Sciences investigated approximately 3,000 glass beads in returned lunar soil samples, and identified three 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 local 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 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.