Water for astronauts

Research team gets cool water from moon dust

(Bild: DLR (CC BY-NC-ND 3.0))

The question of the availability of water is a decisive factor in whether an occupied moon base can ever be realized. A research team with Austrian participation has now produced "simulated", pulverized moon rock - so-called lunar regolith - in the laboratory and extracted over three liters of water from it in several experiments.

As part of an EU-funded project called LUWEX, experts from Germany, Poland, Austria and Italy worked together under the leadership of the German Aerospace Center (DLR) in Bremen and the Technical University (TU) of Braunschweig. The aim was to show how water can be extracted from lunar regolith dust, which contains or adheres to ice.

Thinking carefully about what goes into the moon suitcase
If you look towards a hypothetical lunar base that is repeatedly placed in space by space agencies such as the European Space Agency (ESA) or its US counterpart NASA, you have to think very carefully about what you take with you from Earth at a very high cost and what you can extract on site to keep it in circulation for as long as possible, explains project partner Barbara Imhof from the Viennese space architecture platform Liquifer on the project website.

Together with partners, the expert is thinking intensively about what can be found on the Earth's satellite itself that could be used. In 2023, for example, a method was presented in the journal "Scientific Reports" for using concentrated sunlight to make cobblestones from the lunar regolith.

Moon dust on the surface of the Earth's satellite

(Bild: NASA)

But moon rock or moon dust also contains water in the form of ice. It is not clear how much of this is in places where future bases could be established. However, there are estimates that "in the dark craters at the lunar south pole, up to ten percent of water could be found in the upper layers of the soil", says DLR project manager Paul Zabel: "However, this still needs to be confirmed by on-site investigations."

Tests on "Komet" in Braunschweig, Germany
Nevertheless, the scientists took this as an opportunity to consider technical solutions for extracting the water from the dust. The approach was then investigated at the Comet Physics Laboratory (CoPhyLab) in Braunschweig. However, due to a lack of frozen moon dust, this had to be simulated first.

The team prepared a mixture of dust and ice in extreme cold. This produced a mixture containing spherical ice particles with an average radius of just 2.4 micrometres - which corresponds to around one twentieth of the thickness of a hair, the team said in a press release.

The lunar water extraction system built by the German researchers was then brought into contact with the simulated moon dust in the CoPhyLab - a thermal vacuum chamber designed to recreate the conditions on a comet at temperatures as low as minus 170 degrees Celsius. Up to 15 kilograms of "moon rock" could thus be processed under conditions as close to those on the moon as possible.

The mixture was heated and stirred at the same time in the plant. This turned the ice directly into water vapor, which was then used to anneal on the walls of extremely deep-cooled copper pipes. From there, the water can be virtually harvested again as ice, liquefied and purified.

Process to be developed further
This process therefore appears promising, even though it is "very energy-intensive", as Zabel admits. There are also still some unanswered questions regarding the purification of the water. On the one hand, it is difficult to remove any dust particles smaller than one micrometer from the liquid. "On the other hand, the moon rock has never come into contact with liquid water, so it is very likely that metals such as iron and aluminum or even methanol will dissolve from the dust and get into the water. It is essential that these impurities are removed from the water," says Zabel.

Researcher Paul Zabel examines two samples of water extracted from regolith (on the left the water purified with a treatment system, on the right still contaminated with regolith).

(Bild: TU Braunschweig)

With this approach, a "certain degree of technological maturity has now been achieved". However, according to the DLR scientist, "further development steps are necessary before we are ready for possible initial tests on the lunar surface, which we want to tackle over the next few years".

Great potential for procedures
In any case, the potential is great: the water obtained in this way could be used off Earth as drinking water, for the production of oxygen or as a component of a liquid rocket fuel - for the project partners "a decisive step towards supporting sustainable exploration of the solar system".