August 2021: NASA has no plans to exchange lunar samples with ChinaNovember 2021: China's fresh moon rocks are younger than the Apollo samples and no one knows why...
A first paper published in Science in early October dated a fragment of the samples at about 1.97 billion years old. Now a second,(opens in new tab) published in Nature on Oct. 19, uses a similar dating method but on a different sample, gives an age of 2.03 billion years — very close, geologically speaking. The pair of dates confirms that volcanic activity was taking place in this area of the moon around a billion years after the areas sampled by the Apollo and Soviet Luna missions had become geologically dead.
That finding, in turn, tells scientists about the layer of the moon below the crust. "This means that the mantle had sufficient internal deep mantle heat 2 billion years ago to continue to melt mantle material and produce extrusive mare basalts," James Head III, a professor of geological sciences at Brown University and coauthor on the first paper, told Space.com in an email.
Why the mantle beneath this patch of the moon was still active relatively late in the moon's history remains a mystery, however. Two additional new papers examining the composition of Chang'e 5 samples go against previous thinking on the causes. Existing theories have focused on the heat-producing elements potassium ("K" in the periodic table), rare Earth elements, and phosphorus, together abbreviated as KREEP. Scientists had thought these materials would be relatively abundant in the area, helping to generate the heat required to make the late volcanic activity possible.
But Head's paper and a new study(opens in new tab) in Nature both examined the composition of a portion of the Chang'e 5 samples and found only moderate KREEP content, suggesting the materials are not required for the late volcanism that created these rocks.
"The jury is still out on how and why the late-stage volcanism occurred," Joshua Snape, a planetary scientist at the University of Manchester, told Space.com. "The lack of a KREEP signature that we identified in the Science paper is definitely significant and seems to be confirmed by the studies published in Nature," he added while noting that low KREEP levels cannot yet be wholly ruled out as a factor.
Adding to the mystery is a lack of water found by a team behind a third(opens in new tab) new paper, which looked at hydrogen isotope compositions in the rocks. A relatively high water content would have helped lower the melting point of the rock, making volcanic activity easier. But this paper finds the rocks are dehydrated, suggesting that abundant water in the mantle can't explain the moon's youngest confirmed volcanism either.
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October 2022: Returned samples from Chang'E-5 mission shed new light on moon's surface makeup and geologic history...
"Near-side lunar soil samples we analyzed turned out to be primarily pyroxene," said Prof. Li. "This came as a surprise to us, because earlier remote sensing-based studies indicated a high abundance of olivine—another common volcanic mineral composite in the basalt category."
Studies based on Apollo and Luna-era missions suggested lunar mare (a term for the dark basaltic plains formed by volcanic activity triggered by ancient large asteroid impacts on the far side of the moon) was shaped by active volcanism between 4.3 billion and 3.1 billion years ago, with most of that activity between 3.6 billion and 3.8 billion years ago. Those older studies were based on data collected from Earth-based telescopes as well as moon orbiters, such as NASA's Moon Minerology Mapper.
"Though we can infer a lot about mineral composition of the moon remotely, having actual lunar soil samples here on Earth in our lab for analyses opened up the possibility of a much more thorough and precise compositional analysis," Li said.
Li and his team first analyzed their three soil samples using spectroscopic techniques. "The overall spectral shape of the samples was essentially consistent," Li said. They went on to deploy XRD, which demonstrated the samples were composed of the minerals augite, pigeonite, plagioclase, forsterite, fayalite, ilmenite, quartz, apatite, and glassy materials. The XRD result showed that the samples were composed of mostly pyroxene, not olivine, as earlier studies indicated.
"Preliminary works have identified that the CE-5 returned soil sample is basically comprised of a type of lunar basalt that have never been sampled before," Li and his team wrote in their Oct. 10 paper. "In comparison with the mare samples collected from previous missions, the bulk composition of pyroxene in CE-5 samples is relatively iron and calcium-rich based on electron microprobe analysis."
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March 2023: Water on the Moon stored in glass beads, Chang'e-5 samples revealGlass beads on the surface of the Moon could provide a readily accessible source of water for future missions, a new study suggests.
The researchers, led by Huicun He of the Chinese Academy of Sciences, estimate between 300 billion and nearly 300 trillion kilograms of water is held in tiny glass beads strewn across the Moon.
According to their analysis, published today in Nature Geoscience, water forms from hydrogen delivered in the stream of charged particles flowing from the Sun called the solar wind.
"These findings indicate that lunar soils contain a much higher amount of solar wind-derived water than previously thought," they wrote.This suggested the beads played a central role in the water cycle of the Moon and could be an important reservoir for space bases to tap.
It was once thought that the Moon was dry, but over the past 20 years orbiting spacecraft have detected hydrogen and ice in deep craters at the lunar poles.
In 2020, a team of NASA scientists detected molecules of water in sunlit areas of the Moon for the first time.
They proposed the water could be trapped in glass beads, which would explain why it hadn't evaporated.
Hints of water had previously been found in glass from samples collected by the Apollo missions 40 years ago.
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Dr Norman said the higher water concentration in the Chang'e-5 sample compared with the Apollo samples may be due to the different types of rocks.
While Apollo beads were volcanic glass, Chang'e-5 beads are impact beads.
"A lot of the Apollo missions went to impact craters, [and drilled] into the deeper sub-surface, so a lot of the samples would probably not have been exposed for as long as the Chang'e-5 samples were," he said.
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LOL at the all of the rewriting of scientific history that Apollo return samples also found significance evidence of water on the Moon.