The moon is a treasure trove of valuable resources. Gold, platinum, and many rare Earth metals await extraction to be used in next-generation electronics. Non-radioactive helium-3 could one day power nuclear fusion reactors. But there’s one resource in particular that has excited scientists, rocket engineers, space agency officials, industry entrepreneurs—virtually anyone with a vested interest in making spaceflight to distant worlds more affordable. It’s water.
Why? If you split water into hydrogen and oxygen, and then liquefy those constituents, you have rocket fuel. If you can stop at the moon’s orbit or a lunar base to refuel, you no longer need to bring all your propellant with you as you take off, making your spacecraft significantly lighter and cheaper to launch. That’s important because Earth’s atmosphere and gravitational pull necessitate use of tons of fuel per second when rockets launch. Creating a sustainable source of fuel in space could reduce the costs and hazards associated with heavy liftoffs. One NASA estimate suggests there might be 600 million metric tons of lunar ice to harvest, and other higher-end estimates say one billion metric tons is a possibility.
In other words, if you could mine it effectively, the moon would become a cost-cutting interplanetary gas station for trips to Mars and elsewhere.
Show me the money
Everyone wants a piece of the action. The European Space Agency has a loose vision to build a “moon village” that would include mining operations. China’s Chang’e 5 lunar exploration and sample return mission is thought to be a precursor investigation to understanding more about lunar water content. India’s failed lunar rover mission last August was supposed to map water ice at the lunar south pole.
The US has designs on lunar water too, of course. On May 15, NASA announced the Artemis Accords (PDF)—a proposed legal framework for mining on the moon, named after NASA’s Artemis program to return astronauts to the lunar surface in 2024. Artemis is the most important step toward establishing a permanent American presence on the moon. The tenets touch on issues that include emergency assistance services and interoperability of technology standards. But more importantly, the Artemis Accords reinforce American claims that space mining and claims to space resources are legal. They also propose setting up neutral “safety zones” between different lunar bases to prevent interference and conflict between countries and companies. If most other countries were persuaded to sign the accords, it would allow the US to dictate terms for mining.
But what they can’t tell us is how we’ll actually access the moon’s water. There are plenty of obstacles. The cold temperatures and radiation could endanger humans and degrade sensitive equipment. It’s not ideal to have a large crew of human beings running these kinds of operations day in and day out, but it’s equally unclear how much can be delegated to autonomous systems. Lunar soil itself—coarse and jagged, and prone to sticking to everything—could wreck machinery and pose safety issues to workers in spacesuits. Although we’ve shown the feasibility of refueling satellites in orbit, doing the same thing for large spacecraft on the moon or in lunar orbit will create its own set of challenges thanks to microgravity and regolith, the layer of loose material covering the lunar bedrock.
And we would still need to have astronauts living semi-permanently on the moon’s surface. NASA’s ambitious Artemis plans call for building a lunar base by 2028 (along with a lunar space station called Gateway that’s supposed to facilitate trips beyond the moon),