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No matter where we go in the universe, we will need water. So far, human missions to Earth orbit and the moon have taken water with them. But while that works for short missions, it’s not practical in the long run. Water is heavy, and it would take far too much fuel to bring enough water to sustain long-term bases on the Moon or Mars. So we have to use the water we can get on site.
Fortunately, water is a common molecule in the universe. Even the moon has enough water to support a lunar colony. The only real challenge is extracting them. As a recently published study in Acta Astronautica shows, this could be as simple as putting things in a microwave oven.
Although water is present in minute amounts all over the moon, it is most concentrated in the polar regions. Pockets of ice are concentrated in the shaded regions of the poles. The consistency of these pockets of ice is similar to snow mixed with mostly dusty sand particles. Imagine trying to extract potable water from such material. If you tried to heat it on your stovetop, it would be so dry that it wouldn’t heat evenly. And even if you did manage to melt the ice, you would end up with a wet mud.
Previous studies using simulated lunar material have shown that while traditional conductive heating can extract water, it is not particularly effective. So it takes a lot of power, making it difficult to scale enough to get a colony. So in this study, the team looked at using microwaves to extract water.
If you’ve ever reheated something in a microwave oven, you know that a common problem is that it can sometimes hit and miss. Not only can you get hot regions and icy regions side by side, like a badly cooked hot pocket, you can also heat things up so that they’re slightly soggy. That’s because water molecules are highly excited by microwaves, and your oven can cause them to shift in a material, usually toward the surface. So we have known for a long time that microwave cooking can extract water from material. The team wanted to know if they could work effectively with lunar material.
The team focused on two simulated lunar materials. One simulated the lunar highlands (LHS-1) and one simulated the lunar mare region (LMS-1). They then investigated how efficiently water can be extracted at different ice contents. They found that using a special microwave oven at just 250 watts, they could extract about 55% to 67% of the water in about half an hour. That’s handy enough to get a lot of water out of the polar regions, and the microwave technology they use would be easy to build and maintain on the moon. Interestingly, the method is less effective when you get to higher water content materials where traditional conductive heating is more effective.
James D. Cole et al, Water Extraction from Icy Lunar Simulants Using Low Power Microwave Heating, Acta Astronautica (2023). DOI: 10.1016/j.actaastro.2023.04.035