Scientists at the University of Hawaii have found that electrons from Earth's plasma sheet affect the moon's weathering and may contribute to the formation of water. This discovery deepens our understanding of the relationship between the Earth and the Moon and provides opportunities for future exploration.
A team of researchers led by planetary scientists at the University of Hawaii at Manoa has found that high-energy electrons in Earth's plasma sheet are contributing to the weathering process on the moon's surface and, importantly, these electrons may contribute to the formation of water on the moon's surface. The research was published in the journal Nature Astronomy on September 14.
Understanding the concentration and distribution of water on the Moon is critical to understanding the Moon's formation and evolution and providing water resources for future human exploration. The new discovery also helps explain the origin of water ice previously found in the moon's permanently shadowed regions.
Due to the Earth's magnetism, there is a force field around the Earth called the magnetosphere that protects the Earth from space weathering and damaging radiation from the Sun. The solar wind pushes and reshapes the magnetosphere, forming a long tail on the night side. The sheet of plasma within the magnetotail is a region composed of high-energy electrons and ions, which may originate from the Earth and the solar wind.
Previously, scientists have focused primarily on the role of high-energy ions in space weathering of the Moon and other airless bodies. The solar wind, composed of high-energy particles such as protons, bombards the lunar surface and is considered to be one of the main ways in which water forms on the moon.
Shuai Li, an associate researcher at Mānoa University's School of Ocean and Earth Science and Technology (SOEST), has previously shown that oxygen in Earth's magnetotail is corroding iron in the moon's polar regions.
"This provides a natural laboratory for studying the formation of water on the lunar surface." When the moon is outside the magnetotail, the lunar surface is bombarded by the solar wind. Inside the magnetotail, where there are almost no solar wind protons, water formation is expected to drop to almost zero.
Li and co-authors analyzed remote sensing data collected by India's Moon Mineralogy Mapper instrument between 2008 and 2009. They assessed changes in water formation as the moon passes through Earth's magnetotail, which includes the plasma sheet.
"To my surprise, remote sensing observations showed that the formation of water in the Earth's magnetotail is almost the same as when the Moon is outside the Earth's magnetotail," said Li. "This suggests that there may be other water formation processes or new water sources in the magnetotail that are not directly related to solar wind proton implantation. In particular, the radiation of high-energy electrons exhibits similar effects to solar wind protons. This discovery and my previous discovery of rusty lunar poles suggest that Mother Earth is closely connected to the Moon in many unrecognized ways."
In future research, Li hopes to participate in lunar missions through NASA's Artemis program to monitor the plasma environment and water content on the lunar polar surface as the moon is at different stages of its journey through Earth's magnetotail.