Unlike the landers on Mars which can get covered in dust from wind storms, landers on the Moon don’t. That’s not to say they don’t face other issues, but the Chinese lander Chang’e 5 has been working on the Moon since its December 2020 landing. However, being a stationary lander wasn’t the main purpose. The main purpose of the mission was to collect and return a sample from the Moon back to Earth. New results from the Chinese Academy of Sciences study both the samples and other data the lander took while on the surface. And the result is water… or something pretty close to it.

The “water” source detected was contained in the structure of a mineral called apatite and was 30 parts per million of hydroxyl. Hydroxyl is only one hydrogen and one oxygen, not two hydrogens and one oxygen like regular water. According to scientists, this molecule is what happens when water undergoes photochemical reactions, or reactions involving sunlight. The lunar hydroxyl was discovered in eleven rock and soil samples studied directly by the lander on the lunar surface and confirmed in eight of those samples during laboratory research back on Earth.

The researchers tried to identify other possible sources for this detection. As the sample was collected when the moon was really hot, it should have been dry. Part of the explanation could be from a chemical reaction catalyzed by the solar wind. Apollo moon rocks from Oceanus Procellarum have similar materials. However, the solar wind was not as strong in 2020 as other times when it caused hydration of lunar rocks, so not all the hydroxyl could be explained, which means the rest of the ‘water’ had to come from the moon itself. This water could have influenced the formation of lunar rocks, particularly in the “late lunar” period.

According to project scientist Li Chunlai: By investigating lunar water and its source, we are learning more about the formation and evolution of not just the Moon itself, but also the solar system. In addition, lunar water is expected to provide support for future human lunar in-situ resources.

These results will be followed up by Chang’E 6 and 7.

More Information

CAS press release

“Evidence of water on the lunar surface from Chang’E-5 in-situ spectra and returned samples,” Jianjun Liu et al., 2022 June 14, Nature Communications