China's lunar sample much younger than Apollo's and Luna's: study

The lunar sample brought back to Earth by China's Chang'e-5 mission is much younger than those found by the Apollo and Luna missions, according to participant of recent international research on the sample. The study can be meaningful for future studies on how solar wind affects the lunar surface.

Global experts have measured the maturity index of the lunar soil brought back by the Chang'e-5 mission by using magnetic techniques, shedding light on the space weathering processes occurring on the Moon's surface.

Lunar soil maturity is an index to characterize the space weathering degree of the soil. It is quantified by a variety of indices such as mean grain size, agglutinate abundance and solar wind gas abundance.

Studying the maturity index can reveal the interaction between micrometeorites, solar wind and the lunar surface, and reflect the geological process of lunar soil formation.

The value of Is/FeO (the intensity of the characteristic ferromagnetic resonance normalized to total iron content) is regarded as the only golden standard of lunar soil maturity, according to the research paper published in the journal Icarus.

Researchers from the China University of Geosciences, Wuhan; Brown University and the University of Hawaii used magnetic techniques to measure the maturity index of Chang'e-5 lunar soil and found that its Is/FeO value is between 4 and 20, one of the lowest Is/FeO values obtained so far, indicating that it is among the most immature soils on the Moon.

"This indicates that the lunar soil in the sampling area of the Chang'e-5 mission was exposed to the space environment for the shortest time after formation," said Xiao Long, a professor at the China University of Geosciences, Wuhan.

According to him, based on current studies of Chang'e-5 samples, its landing and sampling unit is much younger than all Apollo and Luna units, which may be the reason why the Chang'e-5 lunar soil is the most immature.

The Chang'e-5 probe returned to Earth on December 17, 2020, retrieving a total of 1.7 kilograms of lunar samples, mainly rocks and soil from the Moon's surface.