A new analysis of dust recovered from the Moon suggests that water bound on the lunar surface may have formed with the Sun.
More specifically, it could be the result of a bombardment of hydrogen ions from the solar wind, pushed on the surface of the moon, interacting with mineral oxides and perturbing the structure of oxygen. The result is water that was hidden in the lunar regolith in significant quantities at medium and high altitudes.
This has implications for our understanding of the origin and distribution of water on the Moon – and also for understanding the origins of water on Earth.
The moon looks pretty dusty, but recent studies have found that there’s a lot more water out there than anyone suspected. There are no lakes and ponds running. bound up in the lunar regolith, perhaps hidden as the perpetual outline of the ice in the craters, and locked away in beads of molar glass.
This naturally leads to the questions, how much water is there? How is it distributed? And where the heck did it come from? The last question probably has several answers.
Some could have come from asteroid impacts. Some from the earth. However, it may be that it is hardly the first thing that comes to mind when cosmic rain clouds are imagined.
To be fair, the Sun is not exactly wet with water, but its wind is the most reliable source of high-velocity hydrogen ions. Evidence that includes analysis of lunar mud from previous Apollo missions has raised the strong possibility that the solar wind is responsible for at least some of the composition of the Moon’s water.
Now, a team of researchers led by geochemists Yuchen Xu and Heng-Ci Tian of the Chinese Academy of Sciences have analyzed the chemistry of grains recovered from the Chang’e-5 mission that supports a further source of lunar solar water.
They studied 17 grains: 7 olivine, 1 pyroxene, 4 plagioclase, and 5 glass. All these, except for the low-latitude specimens, collected from Apollo and the Moon, from the mid-latitudes of the Moon, and from the smallest known lunar basalt, collected from the driest basalt base.
Using Raman spectroscopy and x-ray energy dispersive spectroscopy, the chemical composition of the cracks of these grains – the outer shell, the 100 nanometer grain space is the most exposed to weathering, and therefore the most changed in comparison to the grain. interior
The majority of these cracks show very high hydrogen concentrations of 1,116 to 2,516 parts per million, and very low deuterium/hydrogen isotope ratios. These ratios are consistent with the ratios of these elements found in the solar wind, suggesting that the solar wind pushed onto the Moon, depositing hydrogen on the Moon’s surface.
The water content of the solar wind present in the Chang’e-5 region of the site, they found, should be about 46 parts per million. This is consistent with remote sensing measurements.
To determine whether hydrogen can be stored in lunar minerals, the researchers then performed heating experiments on some of their grains. After burial they found that the grains actually retain hydrogen.
Finally, the researchers conducted simulations of the preservation of hydrogen in the lunar soil at different temperatures. This revealed that temperature plays a significant role in the implantation, migration, and extravasation of hydrogen on the Moon. This implies that a significant amount of water derived from the solar wind can be retained in the middle and high latitudes, where temperatures are cooler.
A model based on these findings suggests that the polar regions of the Moon are much richer in water created by the solar wind – information that could be extremely useful for designing future lunar explorations.
“The lunar polar probe could hold more water than the samples of Chang’e-5,” says cosmochemist Yangting Lin of the Chinese Academy of Sciences.
“This discovery is of great significance for the future use of water resources on the Moon. Also, through particle sorting and heating, it is easy to use the water contained in the lunar soil.”
The research was published in PNAS.
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