By Rebecca Boyle Read more: Click here to read the original, longer version of this story. Sunrise at the Tycho crater, as seen by the Lunar Reconnaissance Orbiter (Image: NASA/Goddard Space Flight Center/Arizona State University) 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 evidence of abundant water, especially at the moon’s poles. 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 where the sun is just rising – the dawn terminator. A lunar “day” lasts a month, 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. “We just drop a clear plastic dome over our collecting surface and let the sun turn it back into vapour,” Livengood says. The vapour then frosts up the inside of the dome, where it can be harvested. Using data taken between 2009 and 2011 by NASA’s Lunar Reconnaissance Orbiter, Livengood calculates that the frost build-up at the terminator would be just under 0.2 millimetres thick – enough to yield about 190 millilitres of water per square metre per lunar day with a suitable set-up (Icarus, doi.org/4ss). “The quantity of water is much less than what we could dig up at the lunar poles, but we get it with very little energy investment on our part,” Livengood says. “We just need to be patient.” The quantity of water is low, but we get it with very little energy investment. We just need to be patient This article appeared in print under the headline “Parched on the moon?