Thirsty moon settlers might enjoy a drink with the help of the sun. At sunrise, its warmth drives water molecules from the lunar soil – ripe for harvest with the right know-how.
Since 2009, several lunar probes have found indirect evidence of abundant water on the moon by looking for hydrogen, since the element is present in water molecules. But no one wants the hassle of mining through the dusty surface to drink it.
The moon's gravity is so low and its atmosphere so tenuous that water molecules in the ground turn directly to vapour when heated. Free to bounce around at near the speed of sound, they condense again when they get cold, piling up as frost where temperatures are low. The greatest build-up is at the dawn terminator: the region where the sun is just rising.
A lunar "day" is a full month long, so the water molecules have a lot of time to accumulate. Tim Livengood of NASA's Goddard Space Flight Center in Greenbelt, Maryland wondered how much drinkable water you could collect if you set up a solar-powered distillery to catch the morning frost.
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