Water on the Moon may have come from Earth’s atmosphere

An additional way to explain how water accumulates on the moon.


NASA has confirmed the presence of water molecules in the sunlit areas of the Moon, indicating that water is widely distributed across the lunar surface.

A majority of the lunar water is generally believed to have been deposited by asteroids and comets that collided with the Moon during the Late Heavy Bombardment period. During that period, the early inner planets and Earth’s Moon were believed to sustain an unusually heavy impact from asteroids.

A new study by the University of Alaska Fairbanks Geophysical Institute suggests that Earth’s atmosphere may be the source of some lunar water. According to scientists, water molecules- H2O- escaping from Earth’s upper atmosphere and combining on the Moon could be the source of lunar water and ice.

How do the water molecules accumulate there?

The solar wind is believed to be a possible source. It may be carrying oxygen and hydrogen ions, which may have combined and been deposited on the Moon as water molecules.

Now, scientists offered another explanation- suggesting that water molecules are driven into the Moon when it passes through the tail of the Earth’s magnetosphere, which it does on five days of the Moon’s monthly trip around the planet.

The Moon’s presence in the magnetosphere’s tail, known as the magnetotail, briefly influences some of Earth’s magnetic field lines, particularly those that are broken and trail off into space for thousands of miles. This presence causes some of these broken field lines to reconnect with their opposing counterparts. When that happens, hydrogen and oxygen ions that had escaped Earth rush to those reconnected field lines and are accelerated back toward Earth.

UAF Geophysical Institute associate research professor Gunther Kletetschka said“Many of those returning ions hit the passing Moon, which has no magnetosphere to repel them. It is like the Moon is in the shower — a shower of water ions coming back to Earth, falling on the Moon’s surface.”

The ions then combine to form the lunar permafrost. Through geologic and other processes such as asteroid impacts, some of that is driven below the surface, where it can become liquid water.

Journal Reference:

  1. Kletetschka, G., Klokočník, J., Hasson, N. et al. Distribution of water phase near the poles of the Moon from gravity aspects. Sci Rep 12, 4501 (2022). DOI: 10.1038/s41598-022-08305-x
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