Map of water content on the surface of the Moon. Credit: Li, et al., 2023
Scientists from the University of Hawai’i found that Earth plasma sheet electrons affect the weathering of the Moon and may aid in the formation of water. This discovery deepens our understanding of the Earth-Moon relationship and points to future opportunities for exploration.
A team of researchers led by a University of Hawai’i (UH) planetary scientist at Mānoa found that high-energy electrons in Earth’s plasma sheet contribute to weathering processes on the Moon’s surface, and importantly, the electrons may have aided the formation. water on the lunar surface. The study was published on September 14 in the journal Astronomy of nature.
Understanding the concentrations and distribution of water on the Moon is essential to understanding its formation and evolution and to securing water resources for future human exploration. The new discovery may also help explain the origin of water ice earlier discovered in lunar permanently shadowed regions.
Earth’s magnetosphere and its effects
The influence of the Earth’s magnetism creates a force field around the planet, referred to as the magnetosphere, which protects the Earth from cosmic weathering and harmful radiation from the Sun. The solar wind pushes and reshapes the magnetosphere, creating a long tail on the night side. The plasma layer in this magnetotail is a region consisting of high-energy electrons and ions that may come from Earth and the solar wind.
Previously, scientists mostly focused on the role of high-energy ions in space weathering of the Moon and other airless bodies. The solar wind, which consists of high-energy particles such as protons, bombards the lunar surface and is thought to be one of the primary ways water formed on the moon.
Graphic showing the magnetosphere and plasma sheet. Credit: NASA/Goddard/Aaron Kaase
Impact of the Earth’s magnetotail on the Moon
Based on his previous work showing that oxygen in Earth’s magnetotail corrodes iron in the Moon’s polar regions, Shuai Li, an assistant research scientist at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), was interested in investigating changes in surface weathering. when the Moon passes through Earth’s magnetotail, a region that almost completely shields the Moon from the solar wind, but not the Sun’s light photons.
“This provides a natural laboratory for studying lunar surface water formation processes,” Li said. “When the Moon is outside the magnetotail, the lunar surface is bombarded by the solar wind.” There are almost no protons in the solar wind inside the magnetotail, and water formation was expected to drop to almost zero.
Li and co-authors analyzed remote sensing data collected by the Moon Mineralogy Mapper instrument aboard India’s Chandrayaan 1 mission between 2008 and 2009. Specifically, they assessed changes in water formation as the Moon passed through Earth’s magnetotail, which includes plasma. sheet.
“To my surprise, the remote sensing observations showed that the formation of water in the Earth’s magnetotail is almost identical to when the Moon was outside the Earth’s magnetotail,” Li said. “This suggests that there may be other formation processes or new sources of water in the magnetotail that are not directly linked to the implantation of solar wind protons. In particular, high-energy electron radiation shows similar effects to solar wind protons.
“Overall, this finding and my previous findings of rusty lunar poles suggest that Mother Earth is strongly tied to her Moon in many unrecognized aspects,” Li said.
Future research avenues
In future research, Li aims to work on a lunar mission NASAThe Artemis programs monitor the plasma environment and water content of the lunar polar surface when the Moon is in various phases during the Earth’s magnetotail transition.
Reference: “Formation of lunar surface water associated with high-energy electrons in Earth’s magnetotail” by S. Li, AR Poppe, TM Orlando, BM Jones, OJ Tucker, WM Farrell, and AR Hendrix, 14 Sep 2023, Astronomy of nature.
DOI: 10.1038/s41550-023-02081-y
