The moon might still have active volcanoes, China's Chang'e 5 sample-return probe reveals

Volcanoes have erupted on the lunar surface within a geologically recent timespan, and the moon could still be volcanically active today, according to tiny glass beads in lunar dirt brought back to Earth by the Chinese Chang'e 5 sample-return mission in December 2020. The discovery could turn what we thought we knew about the evolution of the moon on its head.

We know that the moon had volcanism in the distant past, because we can see the evidence literally all over the face of our nearest neighbor — the dark markings of the famous "man in the moon" are lunar maria, which are vast, volcanic plains dating back three to 3.8 billion years. It was thought that this was the last time the moon was volcanically active.

But, astonishingly, Chang'e 5 brought home evidence that the moon has experienced volcanic eruptions much more recently — just 123 million years ago, give or take an uncertainty of 15 million years.

That still sounds like a long time ago in human terms, but geologically speaking it was just yesterday. It means that the moon may have been volcanically active its whole life, and could still be volcanically active today.

Related: China's Chang'e 5 rover detects hints of water on the moon

The evidence for the recent volcanism came from three tiny glass beads — just three out of 3,000 in Chang'e 5's sample. A team led by Bi-Wen Wang and Qian Zhang of the Institute of Geology and Geophysics at the Chinese Academy of Sciences in Beijing carefully searched the 0.6 ounces (1.7 grams) of lunar dirt recovered by Chang'e 5 for these needles in a haystack. Glass beads, just 20 to 400 microns in size, can be formed by the violent fury of an asteroid impact, melting and pressurizing rock so it turns to glass. Indeed, these impact-derived beads make up the vast majority of the beads in the sample — unsurprising given the number of impacts evident on the moon in the form of craters. But there's another way to form these beads, too.

"Magma fountains produce volcanic glasses, which have previously been found in samples of the moon's surface," wrote Wang and Zhang's team in their research paper. Certainly, glass beads of volcanic origin have been found on the moon before, but always originating from those magma eruptions billions of years ago. However, from its landing site near an area rich in volcanic domes called Mons Rümker in Oceanus Procellarum ("Ocean of Storms"), Chang'e 5 managed to find three glass beads that are very special indeed, returning them to Earth on Dec. 16, 2020.