In June a four-person crew will enter a hangar at NASA’s Johnson Space Center in Houston, Texas, and spend one year inside a 3D-printed building. Made of a slurry that—before it dried—looked like neatly laid lines of soft-serve ice cream, Mars Dune Alpha has crew quarters, shared living space, and dedicated areas for administering medical care and growing food. The 1,700-square-foot space, which is the color of Martian soil, was designed by architecture firm BIG-Bjarke Ingels Group and 3D printed by Icon Technology.

Experiments inside the structure will focus on the physical and behavioral health challenges people will encounter during long-term residencies in space. But it’s also the first structure built for a NASA mission by the Moon to Mars Planetary Autonomous Construction Technology (MMPACT) team, which is preparing now for the first construction projects on a planetary body beyond Earth.

When humanity returns to the Moon as part of NASA’s Artemis program, astronauts will first live in places like an orbiting space station, on a lunar lander, or in inflatable surface habitats. But the MMPACT team is preparing for the construction of sustainable, long-lasting structures. To avoid the high cost of shipping material from Earth, which would require massive rockets and fuel expenditures, that means using the regolith that’s already there, turning it into a paste that can be 3D printed into thin layers or different shapes.

The team’s first off-planet project is tentatively scheduled for late 2027. For that mission, a robotic arm with an excavator, which will be attached to the side of a lunar lander, will sort and stack regolith, says principal investigator Corky Clinton. Subsequent missions will focus on using semiautonomous excavators and other machines to build living quarters, roads, greenhouses, power plants, and blast shields that will surround rocket launch pads.

The first step toward 3D printing on the Moon will involve using lasers or microwaves to melt regolith, says MMPACT team lead Jennifer Edmunson. Then it must cool to allow gases to escape; failure to do so can leave the material riddled with holes like a sponge. The material can then be printed into desired shapes. How to assemble finished pieces is still being decided. To keep astronauts out of harm’s way, Edmunson says the goal is to make construction as autonomous as possible, but she adds, “I can’t rule out the use of humans to maintain and repair our full-scale equipment in the future.”

One of the challenges the team faces now is how to make the lunar regolith into a building material strong enough and durable enough to protect human life. For one thing, since future Artemis missions will be near the Moon’s south pole, the regolith could contain ice. And for another, it’s not as if NASA has mounds of real moon dust and rocks to experiment with—just samples from the Apollo 16 mission.

So the MMPACT team has to make their own synthetic versions.

Edmunson keeps buckets in her office of about a dozen combinations of what NASA expects to find on the Moon. The recipes include varying mixtures of basalt, calcium, iron, magnesium, and a mineral named anorthite that doesn’t occur naturally on Earth. Edmunson suspects that white and shiny synthetic anorthite being developed in collaboration with the Colorado School of Mining is representative of what NASA expects to find on the lunar crust.

Yet while the team feels that they can do a “reasonably good job” of matching the geochemical properties of the regolith, says Clinton, “it's very hard to make the geotechnical properties, the shape of the different tiny pieces of aggregate, because they’re built up by collisions with meteorites and whatever has hit the Moon over 4 billion years.”

There are other X factors to account for when building on the Moon—and a lot can go wrong. Gravity is much weaker, there’s a chance of moonquakes that can create vibrations for up to 45 minutes, and temperatures at the south pole can get as high as 130° Fahrenheit in sunlight and as low as –400° at night. Abrasive moon dust can clog machinery joints and bring hardware to a screeching halt. During the Apollo missions, regolith damaged space suits, and inhaling dust caused astronauts to experience hay-fever-like symptoms.

Constructing Mars Dune Alpha, the test habitat in Texas, had an even bigger X factor: The human race has never brought a sample of Martian soil back to Earth, so Icon had to simulate the material, based on predictions of what it is made out of—such as that it’s rich in basalt. (They call their building material “lavacrete.”) The most important part to NASA officials, says CEO Jason Ballard, was getting the Martian soil’s color match right, to accurately mimic what it would be like to live on the red planet.