Understanding how to breathe lunar regolith

Oxygen is one of the most important resources to be used in space exploration. Not only is it a critical component of rocket fuel, it is also necessary for astronauts to breathe anywhere outside of Earth’s atmosphere. The availability of this abundant resource is not a problem: it is widely available throughout the solar system. One place where it is particularly common is the lunar regolith, the thin layer of material that makes up the surface of the moon. The difficulty comes from one of the quirks of oxygen: it binds to almost everything.

About 45% of the weight of regolith is oxygen, but it is bonded to materials such as iron and titanium. To use both oxygen and the materials to which it is bound must be separated. And a British company, with the support of the European Space Agency, has begun testing a technique to judge its potential effectiveness on the moon.

The company, called Metalysis, already manufactures Earth-bound machines that can isolate metals in oxygen-bound configurations. In a new phase, the company has used its process to extract oxygen and metals from simulated lunar regolith, which is the best proxy here on Earth for real soil on the moon.

The experiment worked well, although it will require fine tuning to increase the amount of oxygen released. The process immerses the oxygen-containing material in a molten salt bath and then flows an electric current through the combined salt and regolith. The electric charge allows oxygen to break its bonds with the metals that hold it in the form of an oxide, and are therefore free to migrate and reunite in a charged electrode. A mixed metal powder is then left.

This metal, when properly harnessed, can be used in material deposition systems such as 3-D printing, but so far this is putting the cart before the horse. The experiment conducted by Metalysis, which takes place in a specialized chamber the size of a washing machine, is extraordinarily energy-hungry and focuses primarily on extracting metal. All three of these characteristics need to be changed if the process is to be used effectively in space.

The chamber itself will have to shrink to reasonably accommodate other space equipment. Energy needs will have to decrease as there is a severe lack of energy available in situ on the moon. And since oxygen is more valuable than metals on the moon, the process will need to be optimized with different reagents to extract the maximum amount of oxygen from the material.

However, Metalysis and ESA engineers still have some time before their process is needed on the moon. The current ambitious plan of NASA’s Artemis program is to return a person to the moon in four years. If there is a system that can create rocket fuel and breathable gas for them upon arrival, it will be a big step towards the safety of future exploration missions from the lunar surface.