THE NEW SPACE RACE: Chinese Lunar Rocks Suggest a Thirsty Far Side of the Moon.

Back on Earth with the Chang’e-6 samples in hand, the researchers sought mare basalts, or hardened grains of lava that erupted from within the lunar mantle. Some of these basalts, as much as 2.8 billion years old, contained olivine, a crystal that formed as ancient magma inside the moon cooled, preserving information about the composition of the mantle early on in lunar history.

The amount of hydrogen trapped in the olivine allowed the scientists to deduce the amount of water present in the mantle back then: between 1 and 1.5 grams of water for every million grams of lunar rock.

Prior measurements from samples collected on the near side of the moon — by the United States, the Soviet Union and more recently China — were as much as 200 times as wet.

The stark difference in the ranges of water content derived from lunar near and far side samples could suggest that the part of the moon invisible to us on Earth is much drier overall, Dr. Hu said.

Or maybe that’s what Beijing wants us to think.