Earth Electrons Contribute to Moon's Water

Scientists determined that high energy electrons in Earth's plasma sheet are contributing to weathering processes on the Moon's surface and may have contributed to the development of water on the lunar surface.

Nature Astronomy reported the research findings.

Understanding the distribution and concentrations of water on the Moon is crucial for understanding its genesis and evolution, as well as providing water resources for future human exploration.

The new discovery could also help explain the creation of previously observed water ice in the Moon's permanently shadowed regions.

Because of Earth's magnetic, a force field known as the magnetosphere surrounds the planet, protecting it from space weathering and harmful solar radiation.

The solar wind pushes and reshapes the magnetosphere, resulting in a lengthy tail on the night side.

This magnetotail's plasma sheet is an area made up of high-energy electrons and ions that could come from Earth or the solar wind.

Scientists previously focused on the role of high-energy ions in the weathering of the Moon and other airless surfaces in space. The solar wind, which is composed of high-energy particles such as protons, bombards the lunar surface and is regarded to be one of the primary sources of water on the Moon.

Shuai Li, the assistant researcher at the UH Manoa School of Ocean and Earth Science and Technology (SOEST), was interested in investigating the changes in surface weathering as the Moon passes through Earth's magnetotail, an area that almost completely shields the Moon from the solar wind but not the Sun's light photons, based on his previous work that showed oxygen in Earth's magnetotail is rusting iron in the Moon's polar regions.

“This provides a natural laboratory for studying the formation processes of lunar surface water,” said Li.

“When the Moon is outside of the magnetotail, the lunar surface is bombarded with solar wind. Inside he magnetotail, there are almost no solar wind protons and water formation was expected to drop to nearly zero.”

Li and colleagues examined remote sensing data collected by India's Chandrayaan 1 mission's Moon Mineralogy Mapper instrument between 2008 and 2009. They looked at how water formation changed as the Moon passed through Earth's magnetotail, which includes the plasma sheet.

“To my surprise, the remote sensing observations showed that the water formation in Earth’s magnetotail is almost identical to the time when the Moon was outside of the Earth’s magnetotail,” said Li.

“This indicates that, in the magnetotail, there may be additional formation processes or new sources of water not directly associated with the implantation of solar wind protons. In particular, radiation by high energy electrons exhibits similar effects as the solar wind protons.”

“Altogether, this finding and my previous findings of rusty lunar poles indicate that Mother Earth is strongly tied with its Moon in many unrecognized aspects,” said Li.