South Korea is getting ready to launch its first mission to the Moon. Among other things, it’ll scope out lunar resources — things like water ice, aluminum, and silicon — that could support future colonies. But it’ll also look for a resource that no one will be able to use for many decades, if ever. Helium-3 is a form of the second-most common element in the universe. While “normal” helium has two protons and two neutrons, helium-3 has only one neutron. Helium-3 could someday be used as a fuel for nuclear fusion. It would produce less radioactive waste than normal helium, and it should “burn” more efficiently. Here on Earth, it’s quite rare — only about three atoms for every 10,000 atoms of regular helium. But it’s a lot more common on the Moon. That’s because there’s a fair amount of it in the solar wind. The Moon has no magnetic field or atmosphere to stop the solar wind, so its particles embed in the surface. So some folks have dreamed of pulling the helium-3 from the lunar dirt and
