The Moon, often perceived as a barren celestial body, may contain more water than previously believed, according to recent research suggesting that some of this water could have originated from Earth’s atmosphere. This discovery adds a new dimension to our understanding of lunar hydration.
Over the past decade, various space missions have detected water on the Moon, primarily in the form of ice near the poles. Other regions may contain water-rich minerals. This finding is crucial for planning future manned lunar missions, as identifying water sources can determine landing sites and support sustained human presence.
The prevailing theory was that the Moon’s water primarily formed from comets and asteroids colliding with it over billions of years. Additionally, some water may have resulted from the impact of solar wind hydrogen and oxygen ions. Another hypothesis links lunar water to the Moon’s formation through a colossal collision between a protoplanet and a young Earth 4.4 billion years ago.
However, researchers from the University of Alaska in Fairbanks propose a new mechanism: Earth’s atmosphere may be a source of some lunar water. This occurs during the Moon’s monthly passage through Earth’s magnetosphere.
Earth’s magnetosphere, a protective bubble of the magnetic field, resembles a comet with a rounded front and a trailing tail extending away from the planet. Approximately every month, for about five days, the Moon traverses through this tail.
During this period, the Earth’s magnetic field lines, which sometimes break, allow hydrogen and oxygen ions from Earth’s atmosphere to escape into space. When the Moon passes through the magnetospheric tail, some of these broken lines rejoin, directing ions back toward Earth. Over time, some of these ions reach the Moon’s surface.
Günter Kletetschka, the lead researcher of the study, compares this process to a “shower,” where water ions from Earth reach the Moon’s surface. Scientists estimate that this mechanism could accumulate around 3,500 cubic kilometers of water at the Moon’s poles over billions of years, based on conservative calculations indicating that only one percent of ions leaving Earth reach the Moon.
