What's on the Moon's far side? China's Chang'e-6 samples reveal first clues

The Chang'e-6 mission samples represent a combination of mature lunar soil mixed with recently ejected materials

For the first time, Chinese scientists have announced the composition of the far side of the Moon, identifying it as a blend of basalts and foreign ejecta, distinct from the predominantly basaltic volcanic rocks previously collected from the near side, according to an article published in peer-review journal National Science Review.

The Chang’e-6 mission samples, according to researchers, might represent a combination of mature lunar soil mixed with recently ejected materials, as evidenced by the fresh impact craters near the landing site.

In China’s initial examination of these far side lunar samples — published less than three months after their return to Earth — the study highlighted that these samples exhibited “unique characteristics” compared to those from the near side, which have been collected since 1969.

Specifically, the far side samples include a notable amount of lighter-coloured particles, such as glass and feldspar, which are absent in the Chang’e-5 samples from the Moon’s near side. Researchers suggest that these materials likely resulted from ejections or impacts.

The new samples exhibit a reduced density, indicating that they are “more loose and porous than previous lunar soils”.

The researchers, in the article, stated, “The lunar sample is quite loose and would be even fluffier in its ‘natural’ state on the lunar surface.” The researchers further stated that the samples were “highly significant for scientific research”.
 

They wrote, “These local mare basalts document the volcanism history of the lunar far side, while the non-basaltic fragments may offer critical insights into the lunar highland crust, [South Pole-Aitken] impact melts and potentially the deep lunar mantle.”
 

This year, China became the first and so far the only nation to collect samples from the far side of the Moon. The country retrieved over 1.9 kg (4.26 pounds) of lunar material from the South Pole-Aitken basin, which is the Moon’s largest, deepest, and oldest impact basin.

The far side of the Moon, which perpetually faces away from earth due to tidal locking, had not been explored until now. Previous missions from the US, Russia, and China, totalling ten in number, had all gathered samples from the near side.