Water from the sun has been found on the moon: ScienceAlert
A new analysis of fabric retrieved from the moon suggests that water bound in the lunar surface could have come from the sun.
More specifically, it could be the result of a bombardment of hydrogen ions from the solar wind, which slam into the lunar surface, interacting with mineral oxides and attaching themselves to the dislodged oxygen. The result is water that could be hiding in the moon’s regolith in significant amounts at mid and high latitudes.
This has implications for our understanding of the origin and distribution of water on the moon – and may even be relevant to our understanding of the origin of water on Earth.
The moon looks like a rather dry ball of dust, but recent studies have shown that it is one much more water up there than anyone ever suspected. It obviously doesn’t float around in lakes and lagoons; to be bound in lunar regolithpossibly lurking like ice in permanently shadowed cratersand enclosed balls of volcanic glass.
That naturally raises questions, such as how much water is there exactly? How is it distributed? And where the hell did it come from? The last question probably has several answers.
To be fair, the sun isn’t exactly dripping with moisture, but the wind is certainly a reliable source of fast hydrogen ions. Evidence that includes an analysis of moon debris from the Apollo missions has previously raised the strong possibility that the solar wind is responsible for at least some of the moon’s ingredients for water.
Now, a team of researchers led by Chinese Academy of Sciences geochemists Yuchen Xu and Heng-Ci Tian has found chemistry in grains retrieved by the Chang’e-5 mission further supporting a solar source of lunar water.
They studied 17 grains: 7 olivine, 1 pyroxene, 4 plagioclase and 5 glass. These were all, unlike low-latitude samples collected by Apollo and Luna, from a mid-latitude region from the moon, and collected from the youngest known volcanic basalt of the moon, from the driest basaltic basement.
Using Raman spectroscopy and energy dispersive X-ray spectroscopy, they studied the chemical composition of the edges of these grains – the outermost, 100 nanometer husk of the grain that is the most exposed to space weather and therefore the most altered compared to the grain interior.
Most of these rims showed a very high hydrogen concentration of 1,116 to 2,516 parts per million, and very low deuterium/hydrogen isotope ratios. These ratios match the ratios of these elements in the solar wind, suggesting that the solar wind slammed into the moon and deposited hydrogen on the lunar surface.
The water content derived from the solar wind present at Chang’e-5’s landing site, they found, should be about 46 parts per million. This corresponds to remote sensing measurements.
To determine whether hydrogen could be stored in lunar minerals, the researchers then performed heating experiments on some of their grains. They discovered that the grains can indeed retain hydrogen after burial.
Finally, the researchers performed simulations on the retention of hydrogen in the lunar soil at different temperatures. This showed that temperature plays an important role in the implantation, migration and outgassing of hydrogen on the moon. This implies that a significant amount of water from the solar wind can be retained at mid and high latitudes, where temperatures are cooler.
A model based on these findings suggests that the polar regions of the Moon could be much richer in water created by the solar wind – information that could be very useful in planning future lunar exploration missions.
“The polar lunar soils may hold more water than Chang’e-5 samples,” says cosmochemist Yangting Lin from the Chinese Academy of Sciences.
“This discovery is of great importance for the future use of lunar water resources. Particle sorting and heating also make it relatively easy to exploit and use the water in the lunar soil.”
The research has been published in PNAS.
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