The uncertainty of science: In a paper published yesterday, Chinese scientists revealed that data from an instrument on the Chang’e-5 lunar lander has detected evidence of very tiny amounts of water in lunar soil, amounts that confirm past data showing the Moon is very dry.
From China’s state-run press:
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 a light, vesicular rock carries 180 ppm, which are much drier than that on Earth. … The additional 60 ppm water in the rock may originate from the lunar interior, according to the researchers. [emphasis mine]
It is believed that most of this water is the result of hydrogen in the solar wind.
The paper can be found here.
Before we begin dancing in joy that the Moon is wet, reread the highlighted words. This data instead simply confirms past data that the Moon is very dry. In the paper itself, it is made very clear that this high water content, small as it is, was only detected in a single rock, with all of the surrounding terrain much much drier. From the paper:
The water contents are less than 30 ppm in most measured regolith spots except for [areas] D12 and D17, which may be due to the disturbance of the top layer of the more space-weathered/solar wind–implanted regolith by the lander exhaust and the subsequent sampling process. The unsampled areas of D12 and D17 may have been shielded by [a rock] from the lander exhaust and thus retain the top space-weathered layer that contains higher water content. We predict that higher water content may be found in surface regolith than that from the subsurface of the returned borehole samples if the original stratigraphy is preserved. The estimated water contents of the regolith in the landing area are in agreement with those measured in the Apollo regolith samples and the orbital observations.
In other words, the higher water content, still very dry, appears to only exist on the surface, which is why they suspect it is produced by the solar wind and is also very temporary.
Moreover, there are many uncertainties in this result. The detection might not even be water, but hydroxyl molecules.
What this study suggests is that the patches of suspected water that some orbiters think they have identified in low latitudes on the Moon may simply be these surface molecules left by the solar wind, and that if there is usable water on the Moon, it will only be found in those permanently shadowed craters at the poles, if there.
