A recent study from China has revealed that the Moon's farside mantle contains significantly lower water content compared to the nearside, based on rock samples collected during the Chang'e-6 lunar mission.

The analysis indicates that the water content in the farside's mantle is between 1 and 1.5 micrograms per gram, or less than 2 parts per million, marking the driest values ever recorded in lunar geology.

In stark contrast, even Earth's driest desert contains approximately 2,000 parts per million of water, highlighting the significant disparity in water abundance between our planet and the Moon's far side.

These findings have important implications for understanding the Moon's formation, particularly in supporting the giant-impact hypothesis, which suggests that the Moon formed from a high-temperature impact event 4.5 billion years ago.

The low water content strengthens this impact hypothesis, suggesting that if water levels were higher, current theories about the Moon's formation would face more scrutiny.

One hypothesis posits that the impact creating the South Pole-Aitken basin may have displaced water elements to the near side, contributing to the observed dryness on the far side.

The study analyzed 5 grams of soil samples collected by the Chang'e 6 spacecraft from the South Pole-Aitken basin, the largest impact crater in the solar system, allowing for the first direct assessment of the far side's water content.

This analysis included a sample comprising 578 particles, with 28 percent identified as mare basalt fragments, further informing the study's conclusions.

Previous estimates of lunar water content were based solely on nearside samples, which reported levels ranging from 1 to 200 micrograms per gram, contrasting sharply with the new findings.

The implications of this research extend to future lunar missions, particularly China's plans for a permanent base and crewed landings before 2030, emphasizing the importance of navigation systems and water availability for long-term human presence.

Conducted in collaboration with Nanjing University and supported by various Chinese scientific organizations, the study was led by Professor Hu Sen from the Chinese Academy of Sciences and published in the journal Nature.

Scientists caution that more samples from the far side are needed to accurately assess the extent of dryness and to further understand the Moon's geological evolution.