Charged particles wafting from Earth might help to keep the Moon hydrated.
Earth might be blowing some of the raw ingredients for water to the Moon.
Charged particles flowing from the Sun bombard the Moon’s surface. Among them are protons, which bond with oxygen to make some of the Moon’s water. But for several days a month, Earth lies between the Moon and the Sun, blocking the flood of solar particles.
Jiang Zhang and Quanqi Shi at Shandong University in Weihai, China, and their colleagues used data from the Chandrayaan-1 spacecraft to map water at the Moon’s poles. They found that water levels remain about the same all month, and don’t change during the period when Earth shields the Moon from the solar wind.
During that period, charged particles from Earth’s protective magnetic shield might be blowing to the Moon, where they would pelt the surface and create water much as those from the solar wind do. In this way, Earth’s ‘wind’ might serve as a bridge to the Moon, providing an additional source of water.