The moon is covered in fine, delicate dust called regolith which sticks to absolutely everything and causes all sorts of technical problems. But it is an abundant resource, and plans for making use of it include melting it with lasers to use for 3D printing or packing it into bricks to build habitats. Now, the European Space Agency (ESA) has come up with a different use for the tricky substance: Turning it into oxygen which could be used by lunar explorers for breathing and for the production of fuel.
Moon regolith is known to contain about 40 to 50% oxygen by weight, but it is bound in the form of oxides so it’s not immediately usable. Researchers at the European Space Research and Technology Centre (ESTEC) have been investigating ways to extract this oxygen using a technique called molten salt electrolysis. The regolith is placed in a metal basket along with molten calcium chloride salt and heated to a high temperature, then an electric current is passed through it so the oxygen can be extracted. A bonus of this method is that it also produces usable metal alloys as a by-product.
Artist impression of activities in a Moon Base. Power generation from solar cells, food production in greenhouses and construction using mobile 3D printer-rovers. ESA – P. Carril
This technique was originally developed by the company Metalysis, which wanted a way to extract the metal alloys and considered oxygen the by-product. But scientists realized they could apply the technique to moon exploration. “At Metalysis, oxygen produced by the process is an unwanted by-product and is instead released as carbon dioxide and carbon monoxide, which means the reactors are not designed to withstand oxygen gas itself,” Ph.D. student Beth Lomax of the University of Glasgow explained in a statement. “So we had to redesign the ESTEC version to be able to have the oxygen available to measure. The lab team was very helpful in getting it installed and operating safely.”
Now the researchers are considering how these metal alloys might also be useful for lunar explorers. “The production process leaves behind a tangle of different metals,” ESA research fellow Alexandre Meurisse said. “And this is another useful line of research, to see what are the most useful alloys that could be produced from them, and what kind of applications could they be put to. Could they be 3D printed directly, for example, or would they require refining? The precise combination of metals will depend on where on the Moon the regolith is acquired from — there would be significant regional differences.”