We know there is ice on the moon – it’s less clear where it came from. A new study suggests that electron waves, coming indirectly from Earth and the Sun, contribute to the formation of frozen water on the lunar surface.
These electrons strike the Moon as it passes in and out of the Earth magnetotailthat our planet leaves behind as it hurtles through space.
Inside the magnetotail is a layer of plasma composed of highly charged electrons and ions drawn from Earth’s atmosphere and solar wind radiation from the Sun.
Scientists have previously looked at the role of the magnetotail and the larger magnetosphere in the formation of lunar water. The magnetosphere is formed when Earth’s protective magnetic field repels the Sun’s solar wind, creating various effects in its wake.
“This provides a natural laboratory for studying lunar surface water formation processes,” he says planetary scientist Shuai Li of the University of Hawai’i at Mānoa.
“When the Moon is outside the magnetotail, the lunar surface is bombarded by the solar wind. There are almost no solar wind protons inside the magnetotail, and water formation was expected to drop to almost zero.”
However, remote analysis suggests that this is not the case. Earlier studies pointed to hydrogen ions from the solar winds generating water on the moon, but this water appears to still form when the lunar surface is shielded from the solar winds, inside the magnetotail.
Scientists think there are other forces at play—namely, electrons. One way this can happen is through high-energy electrons reacting with the lunar soil to release the trapped hydrogen which can then form water.
“There may be other formation processes or new sources of water in the magnetotail that are not directly related to the implantation of solar wind protons,” he says If. “In particular, high-energy electron radiation exhibits similar effects to solar wind protons.”
More observations and experiments on the lunar surface will be needed to know for sure, but it’s an intriguing suggestion — one of many that scientists are investigating to try to determine where lunar water first appeared.
And there are many reasons why the moon’s water source fascinates scientists: It teaches us more about its past, and it’s also vital to figuring out how we might live long-term on the lunar surface.
“Overall, this find and my previous findings of rusty lunar poles suggest that Mother Earth is strongly tied to her Moon in many unrecognized aspects,” he says If.
The research was published in Astronomy of nature.
