NASA has its sights set on establishing a permanent base on the moon within the next decade, which means infrastructure and construction. Now, samples of potential moon-based building materials have spent six months in space, and some of them came back stronger.

The trick with construction on the moon is that we need to either take materials with us or use what is already there.

A lab at the University of Delaware is developing geopolymers (concrete-like substances made from natural materials and chemical activating solutions) that can be made on the moon using lunar dust known as regolith.

The lab made four types of geopolymers using different source materials:

• Simulated lunar regolith (aka moon dust)
• Samples from the Black Point basalt flow in Arizona
• Simulated Martian regolith
• Commercially available mineral known as metakaolin (on Earth, obviously, not on the moon).

(MORE: NASA fast-tracks its plans for a moon base with 3 launches in 2026)

Samples were then sent to space and attached to the outside of the International Space Station for six months, where they were exposed to low-Earth orbit conditions, like temperatures ranging from about 11 degrees Fahrenheit to 95 degrees.

As a related aside, the moon’s South Pole, where NASA plans to build its future base, ranges in temperature from as low as minus 334 degrees Fahrenheit in the permanently shaded areas to 130 degrees in the sunnier spots.

Once the geopolymers returned to Earth, they were tested for strength and chemical composition to see if anything changed compared to control samples left behind.

Not only did three out of the four materials show no sign of degradation, but the lunar regolith simulant was 35% stronger than the control sample that remained on Earth.

What comes next?

This is just one step of many that will eventually allow us to achieve the goal of a permanent base on the moon, but it is an important one. The use of lunar dust in geopolymers would reduce the amount of material needed to be flown to the moon ahead of construction.

(MORE: From the moon to Mars: What’s next for NASA’s Artemis mission?)

Instead of taking everything with them, NASA and its partners will be able to transport an activating solution that can turn the dust already there into usable materials for future infrastructure, like landing pads, radiation shielding and transportation.

Now that geopolymers made of lunar regolith have been proven to be viable options for construction and development of the future moon base, the next stages for research like this will include testing materials on the moon itself and optimizing the geopolymers to use less activator compound, resist degradation from micrometeorite strikes and remain stable under the actual temperature conditions of the moon.

There’s still a lot of work to be done, but this is a big step for humanity’s future in exploring space, the final frontier.

Sara Tonks is a content meteorologist with weather.com and has a bachelor’s and a master’s degree from Georgia Tech in Earth and Atmospheric Sciences along with a master’s degree from Unity Environmental University in Marine Science.