For billions of years, the Moon’s almost airless surface has been exposed to the solar wind, letting helium-3 become trapped in its soil — making the Moon the most tempting nearby reservoir of a fusion fuel that is almost nonexistent on Earth.

The Moon has no helium-3 mine, and no power grid on Earth is waiting for lunar fuel to arrive. The attraction begins with a simpler physical fact: most of the lunar surface sits exposed to the solar wind in a way Earth does not. That exposure has been going on for a very long time. [...] The post For billions of years, the Moon’s almost airless surface has been exposed to the solar wind, letting helium-3 become trapped in its soil — making the Moon the most tempting nearby reservoir of a fusion