Chinese scientists published results of in-situ detection of water signals on the moon by the Chang'e-5 lunar lander, lending new evidence to the dryness of the satellite. The study published on Saturday in the peer-reviewed journal Science Advances revealed that the lunar soil at the landing site contains less than 120 ppm water or 120g water per ton, and vesicular rock carries 180 ppm, which are much drier than that on Earth.

A device onboard the lunar lander measured the spectral reflectance of the regolith and the rock and detected water on the spot for the first time. The water content can be estimated since the water molecule or hydroxyl absorbs at a frequency of about three micrometers, according to researchers from the Chinese Academy of Sciences (CAS).

It was the solar wind that contributed to the most humidity of lunar soil as it brought hydrogen that makes up the water, the researchers said. The additional 60 ppm water in the rock may originate from the lunar interior, according to the researchers.

Therefore, the rock is estimated to hail from an older, more humid basaltic unit before being ejected onto the landing site to be picked up by the lunar lander. The study revealed that the moon had turned drier within a certain period, owing probably to the degassing of its mantle reservoir.

The Chang'e-5 spacecraft landed on one of the youngest mare basalts located at a mid-high latitude on the moon. It measured water on the spot and retrieved samples weighing 1,731 grams.

Science fiction authors have been thinking about water on the moon, and what it might be used for, for a long time. In his 1931 classic A Daring Trip to Mars, Max Valier described looking for water on the moon and harvesting it for use as fuel:

The engineer had judged correctly for the ground on which the space ship had landed consisted of ice...

"...Now be quick, get out the solar power apparatus and send it down to us from the air-lock by the crane."

A huge parabolic mirror built of light sheet silver collected the intense heat of the sun and first melted a small amount of ice in a closed container. The water thus formed - which cannot exist free on the airless moon - was heated to boiling, and provided the steam for a little turbine. This was connected with a generator of electric energy, whose current was used for the electrolytic dissociation of melted ice in special containers.

The entire system was of such dimensions that in four terrestrial days it would exactly fill the tanks of the ship with liquid hydrogen and oxygen in the right proportions.