Between 1969 and 1972, Apollo astronauts brought just under 842 pounds of rocks and regolith back from the Moon. In 1985, engineers at the University of Wisconsin discovered significant amounts of Helium-3 in the lunar soil.

Helium-3 is a stable isotope of helium — the gas we use to fill party balloons with — and is notable because it’s missing a neutron, an important property that means we can used it in nuclear fusion reactions to produce clean energy. Unfortunately, our most plentiful stores of the isotope are a quarter of a million miles away.

ANALYSIS: This Moon was Made for Mining (Helium-3)
Current nuclear power plants use fission reactors, splitting uranium nuclei to release energy. This heat turns water into steam that drives a turbine to produce electricity. Unfortunately, radioactivity, spent nuclear fuel reprocessed into uranium, plutonium, and radioactive waste are by-products of this reaction.

To get away from fission power, scientists have been working on nuclear fusion energy.

Nuclear fusion is the same reaction that fuels the sun; high temperatures and dense concentrations of gas allow positively-charged nuclei to get close enough to each other that the attractive nuclear force overcomes the repulsive electrical force. They fuse, producing new elements and energy. Helium as the fuel in this type of reaction can provide energy without radioactivity and nuclear by-products.

Fusion reactors fueled by tritium and deuterium — both isotopes of helium — lose more energy than they produce, making them poor fuel sources. But fusion reactions between Helium-3 and deuterium, which creates normal helium and a proton without a neutron, wastes less energy. It’s the proton that’s important; manipulating it in an electric field produces energy. The Helium-3 fusion process is about 70 percent efficient compared to coal and natural gas, which are only about 20 percent efficient.

ANALYSIS: Asteroid Forensics May Point to Alien Space Miners
So we know how to harness the energy potential in Helium-3 (even though the technology to do so efficiently is a few years off), we just don’t have enough of it on Earth to make it a viable energy source. That’s because Helium-3 is carried by the solar wind and has a hard time getting through our planet’s magnetic field.

We can make it — tritium, hydrogen with two neutrons, and deuterium, hydrogen with an extra neutron, both decay into Helium-3. It’s also a byproduct of nuclear weapons testing. But this still isn’t enough. The United States’ entire Helium-3 reserve is a little under 65 pounds; a country this size would need about 50,000 pounds — 25 tons — for a year’s worth of power.

The moon’s lack of magnetic field means Helium-3 can build up on its surface. As Apollo 17’s lunar module pilot Harrison “Jack” Schmitt sees it, there are very few disadvantages to mining Helium-3 from the moon. Aside from it being a hard thing to do. Hard, but not impossible.

Schmitt has pointed out that we more or less know how to get to the moon — we’ve been there — so we can estimate the cost and figure out whether it would be worth the investment. Then we’d have to set up a base on the moon before starting to mine the isotope. We would also need a steady stream of shuttles between the Earth and the moon to bring canisters of Helium-3 back.

The only real downside, says Schmitt, is that mining the moon will force people to work in the dangerous and punishing lunar environment. (Though with a stunning view of the Earth I think many would accept the job hazards with a smile.) It might even open up a new branch of the tourism industry: ride to the moon and back next to a batch of Helium-3 canisters!

ANALYSIS: Strip Mine the Moon to Fuel Space Exploration
But there’s an ethical question to ask beyond space-labor laws. Do we strip the moon, potentially destroying its appearance in the night sky, for clean energy source for Earth? Schmitt says yes, but his opinion isn’t shared by everyone.

Another moonwalker is inclined to leave the moon alone. Apollo 14′s lunar module pilot Ed Mitchell says going to the moon was a turning point for him. Looking up at the Earth he realized that we on our planet are a tiny speck in the larger scheme of things. We ought to explore, he says, without consuming the resources of one planet after another as we go. In our rush to exploit the resources on planets and satellites, we might miss to exciting science that’s right in front of us. Before trying to leave Earth, we ought to learn to live within our means.

There’s another tricky side to mining the moon, and that’s the political aspect. It could happen that the first nation to land and establish a mining operation on the moon will get the monopoly over the resources and, by extension, the world’s energy. It could end up being a multinational endeavor, a group of nations taking on the expensive task of establishing a base, mining the Helium-3, and transporting it back to Earth.

Of course, if none of these mining ventures come to fruition, there’s still the possibility of using the stores of Helium-3 on the moon as an interplanetary gas station. Instead of carrying all the fuel a mission or crew would need, the spacecraft could stop on the moon, mine enough Helium-3 to fuel the mission, then set off into deep space. That sounds like an equally exciting prospect.