how do you extract water that is likely locked up as small concentrations of ice in the lunar soil? Microwaves could provide the key, according to work by Edwin Ethridge of NASA’s Marshall Space Flight Center and William Kaukler of the University of Alabama, both in Huntsville, who first demonstrated the technique in 2006.
They used an ordinary microwave oven to zap simulated lunar soil that had been cooled to moon-like temperatures of -150 °C.
Keeping the soil in a vacuum to simulate lunar conditions, they found that heating it to just -50 °C with microwaves made the water ice sublimate, or transform directly from solid to vapour. The vapour then diffused out from higher-pressure pores in the soil to the low-pressure vacuum above.
Extracting lunar water woudl use 100 times less energy as would be needed to extract hydrogen and oxygen from the lunar soil.