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.
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 astatement. “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.”