How do you find water on the Moon?
“We have a very good idea of where we can find it,” says Kiewiet, a researcher at DLR, the German Aerospace Center(opens in new window). “It must be near the poles.” Liquid water cannot exist on the Moon, because of the deep vacuum of space. With almost no pressure from the atmosphere, a drop of water would simply turn to gas, and float around the surface until it reached a spot cold enough to condense as ice, where it would remain for a long period of time. So the most promising water spots for rovers or astronauts to look – and where we’ve found some evidence of it – is at the lunar poles. Here, large, deep craters are permanently shadowed from the sun, providing the constant cold necessary for ice to survive for potentially billions of years. Back in 2009, NASA’s LCROSS mission targeted a crater near the Moon’s south pole in search of water ice. On reaching the Moon, a spent part of the rocket deliberately crashed into the crater to eject a plume of debris. A trailing scientific probe then flew through the plume to analyse it – and found clear evidence of water. Other modelling suggests water ice could exist in ‘micro cold traps’: regions just below the lunar surface that appear to be cold enough. “That would be good, because those are much easier to reach,” says Kiewiet. “Not having to go four kilometres deep into an extremely cold crater with your tiny rover is, of course, much, much better,” he adds. Finding water on the Moon is key for future space missions, either for establishing lunar bases or for fuelling space travel. Lunar water could be converted into rocket fuel, for astronauts to either return to Earth – or perhaps journey onward to Mars. In the LUWEX project, Kiewiet and his colleagues developed a system designed to process lunar regolith and extract water from it. They tested their system on simulated regolith in conditions similar to that on the lunar surface, purifying the extracted water through a series of methods. They successfully gathered water that either would be safe enough for astronauts to drink, or could be turned into rocket fuel. Remote observations are used to search for potential water sources on the Moon, though these can only look a few metres below the surface. So it’s possible, Kiewiet says, that if we dig deeper, we could find larger chunks of ice. “This is very much unknown, but the hope is, of course, that there is more so we can utilise more,” he notes. Also of interest to space agencies are the rims of large, permanently shadowed craters on the poles. If you were standing on one of these rims, you’d be in almost permanent sunshine, likely with water ice at your feet. “You have the resource that could most easily provide you with a good propellant for your rockets,” explains Kiewiet. “And right next to that is the place where you can most easily harvest solar energy.” Click here to find out more about Luca Kiewet’s research: A water extraction system for the Moon.