How to extract water from the lunar soil? Scientists try microwaves

The team was able to extract 55 to 67 percent of the water using a low-power microwave oven (only 250 Watts). 
Mrigakshi Dixit
Earth's moon.

Water is known to be locked in pockets across many locations on the lunar surface. Scientific evidence has already shown that water can be found in the grains of the surface lunar dust, while a higher concentration of water is locked in the permanently shadowed regions at the poles of the Moon.

The Moon stores enough water collectively to support a future lunar colony. However, it is not easily accessible for drinking or other uses, and the real challenge is figuring out how to extract it.

A new study by researchers from the Open University and the University of Central Florida proposes a simple method for extracting this water. Thirsty astronauts could do so by simply microwaving a cup of Moon soil. According to a report, this technology is based on the principle that water molecules become highly excited when exposed to microwave heat. Once heated, the microwave causes the water molecules in the material to be heated to migrate to the surface. To put it into perspective, when you reheat your pizza slice, the surface occasionally releases some water. That’s exactly the case here. 

The team attempted to test this method on the water molecules found in lunar soil.

Extracting water from the lunar soil

This method was tested on two versions of simulated lunar regolith samples in this study: lunar highlands (LHS-1) and lunar mare region (LMS-1). Following that, the researchers assessed how efficiently water could be extracted from samples with varying levels of ice content.

This technique was successful in extracting some amounts of water from the simulated lunar sample. Surprisingly, the team was able to extract 55 to 67% of the water in less than half an hour using a low-power microwave oven (only 250 Watts). 

However, this experiment also demonstrated that the method is less effective on materials with higher water content. “Water-saturated samples show low extraction compared to low-water-content samples,” highlighted the research paper.

The microwave technology employed in the study is said to be simple to construct and maintain on the Moon. 

The results have been published in the journal Acta Astronautica. 

Study abstract:

Identifying the best technique for extracting water ice deposits in permanently shadowed regions at the lunar poles will be crucial in determining how successful a long-term or permanent settlement at these locations will be for future scientific and technology missions. This study uses a low-power microwave heating method to extract water from icy lunar simulants. Samples of lunar highland and mare simulants at different water contents (3–15 wt %) were heated using 250 W, 2.45 GHz microwaves. A maximum of 67 ± 5% [2SD] of the water was extracted during heating runs of 25 min. Water was extracted more efficiently from the highland simulant than from the mare simulant. A significant reason for the different efficiency of water extraction in icy lunar simulants was the differing porosity of the samples made from different simulants. Pore space filled with ice leads to a reduced contact area between grains and an increased area of free ice, which causes poor heating performance. The results indicated that differences in chemical composition between the simulants had a negligible effect on water extraction, as the contact area between grains seems to dominate water extraction. This study found that low-power microwave heating is an effective technique for extracting water from cryogenic Icy simulants. It was also found that using a simple input energy principle (Input Energy = Absorbed Power x Heating Time) to estimate the additional heating time was sufficient to overcome inefficient heating due to differing absorbed powers. For undersaturated samples, microwave heating was an efficient heating mechanism, but is less efficient for saturated samples where alternative heating methods may be more efficient at melting free ice before employing microwave heating.

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