Context

According to a new study, some of the water deposits that scientists believe exist on the moon may have an unexpected source — the atmosphere of Earth.

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Key findings of the study:

• Hydrogen and oxygen from Earth combine to form water on the Moon.
• This process may have created up to 3,500 cubic kilometres of surface permafrost (water ice) or subsurface liquid water.
• The theory has its roots in the earth’s magnetic field, according to the study.
• As the moon orbits the Earth, it passes through the magnetosphere, a vast comet-sized bubble around the planet created by the earth’s magnetic field.
• It keeps the solar material from entering the earth.
• Some of Earth’s magnetic field lines break and trail off into space for thousands of miles.
• The magnetosphere vigorously flaps like a flag in the wind in response to the pressure from the solar wind, the expert highlighted.
• It compresses on the dayside of Earth and stretches into a long tail on the night side.
• The Moon, during its transit, is completely submerged inside the Earth's magnetic field.
• As it passes through the long tail, some of these broken field lines reconnect with their opposing broken counterpart.
• During this time, oxygen and hydrogen ions in the upper parts of the atmosphere (ionosphere), between 80 kilometres and 600 km above the surface, move towards the reconnected lines.
• The presence of water-forming ions as the moon transits through this part of the magnetosphere was established by data from NASA, the European Space Agency, the Japan Aerospace Exploration Agency and the Indian Space Research Organization.
• Some of these ions return to the earth and are likely to fall on the moon.