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Jan 3, 2023
We are still only at the beginning of the exploration of the Moon and many surprises about it still await us. But already, before the future return to Earth of samples from the Artemis mission, cosmochemists and lunar planetologists believe they have discovered new lunar rocks in samples from the Chinese Chang'e 5 mission.
Image above: The Mons Rümker region, in the Stormy Ocean, landing site for the Chang'e 5 mission. Image acquired by NASA's LRO probe. Image Credits: NASA/LRO.
The return of Man to the Moon is imminent with Artemis and even instantaneous if we consider the geological time scale which is counted with a million years as a unit of time. The Apollo missions brought back to Earth samples of lunar rocks that we continue to study today. Magically, it is not necessary 50 years after the Apollo (USA), Luna (USSR) and Viking missions to be a member of a world-class research laboratory to possess lunar or Martian meteorites nor to be millionaire. It is possible to acquire some for a few tens of euros.
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Image above: Exotic clasts identified in regolith samples from Chang'e 5. Image Credit: Chinese Academy of Sciences.
On the other hand, you still have to be to have the chance to analyze the lunar samples brought back to Earth by the Chinese Chang'e 5 mission, as evidenced by an article published in Nature Astronomy and resulting from the work carried out by a team of the Institute of Geochemistry of the Chinese Academy of Sciences.
The material taken by the probe comes from the regolith that can be found in the Mons Rümker region north of the Ocean of Storms, in Latin Oceanus Procellarum, the largest of the lunar seas. Stretching more than 2,500 kilometers along its north-south axis, it is located west of the visible side of the Moon.
Unknown Lunar Volcanism?
The lunar regolith is believed to be the product over the past billion years of ejecta of material produced by collisions of small celestial bodies of all sizes with the surface of the Moon. It is generally estimated that a core in one meter of regolith covers a billion years of its deposit. Regolith samples must therefore make it possible to highlight fragments from several lunar regions and over a certain time range. We can also roughly estimate the age of a lunar terrain according to its cratering rate, the lower it is, the older the region is on average.
Selenologists found in samples from Chang'e 5 that the probe landing zone was rich in a type of basalt formed two billion years ago, which is younger than samples from the Apollo missions and Luna.
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Image above: A diagram explaining how the exotic Chang'e 5 clasts likely formed. Image Credit: Chinese Academy of Sciences.
Technically, as the abstract in the published paper explains, researchers studied in the regolith samples brought back to Earth in December 2020 more than 3,000 particles less than 2 mm in diameter. They classified them into seven exotic igneous clasts, that is to say that these particles were themselves assemblies of rock fragments of different natures but related to volcanic and magmatic processes.
We thus distinguish, for example, a vitrogenic component with a high titanium (Ti) content, a basaltic component with a low Ti content, one of the olivine-pyroxenite type, one of the magnesian anorthosite type and in the end three of the clasts presented petrological characteristics. and unusual composition. The high-titanium vitrophilic clast, with larger crystals embedded in glassy rock, has mineralogy that has never been seen before on the Moon, and likely represents a new type of moon rock according to Chinese selenologists.
Chang'e 5 lunar rover. Animation Credit: CNSA
Volcanic glass from a volcanic eruption on the Moon with a unique chemical composition has also been identified. It suggests the presence of additional and as yet unrecognized past lunar volcanic eruptions.
Related links:
Nature Astronomy: https://www.nature.com/articles/s41550-022-01840-7
Chinese Academy of Sciences: https://english.cas.cn/
China National Space Administration (CNSA): http://www.cnsa.gov.cn/english/index.html
Images (mentioned), Animation (mentioned), Text, Credits: Chinese Academy of Sciences (CAS)/Futura/Orbiter.ch Aerospace/Roland Berga.
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