ANKARA

Chinese scientists have claimed to have solved the mystery of why soil from the far side of the moon differs from soil from the near side, a discovery that could influence how future lunar bases are built, state media reported on Monday.

Researchers had noticed that the soil collected by China's Chang'e 6 space mission from the far side of the moon in 2024 was unexpectedly sticky, whereas the moon dust brought from the near side by previous missions was loose and sandy, the China Daily reported.

In a study published Monday in the journal Nature Astronomy, scientists from the Chinese Academy of Sciences reported that the soil's "stickiness" stems from a combination of extremely fine particles and jagged, irregular shapes.

The investigation began in June last year after Hu Hao, chief designer of the Chang'e 6 mission, noticed that the soil collected from the South Pole-Aitken Basin appeared "slightly more viscous and somewhat clumpier" than samples from the near side.

Following a series of tests by a team led by Qi Shengwen at the Institute of Geology and Geophysics, they found that the far-side soil could hold a much steeper slope, behaving more like damp garden soil on Earth than dry beach sand.

Using high-resolution CT scans of more than 290,000 individual grains, the team found that particles from the far side are extremely small—averaging 48.4 microns in diameter—yet unusually jagged and sharp, thus creating a "perfect storm" for stickiness.

The roughness increases friction between the grains, locking them together. And because the particles are so small, they are subject to weak forces that are negligible on human scales: static electricity and Van der Waals forces, in which molecules are naturally attracted to one another.

"This is unusual," Qi said. "Typically, finer particles are more spherical. Yet, the Chang'e 6 soil, despite being fine, has a more complex shape."

*Writing by Aamir Latif