Made on Mars

Interest in Mars is increasing - as made evident by projects such as Mars One. With growing interest in establishing human civilization on Earth's distant neighbor, there is also growing awareness of the challenges that need to be overcome in order to do so. One of these is constructing buildings where settlers can live and work.

The Northwestern University research scientists Lin Wan, Gianluca Cusatis and Roman Wendner have found one possible solution. They managed to create a type of concrete using materials that naturally occur on Mars: sulfur and soil. They did it by heating the sulfur to a high temperature so that it became liquid and then mixing it with the soil. Unlike traditional concrete, this "Martian concrete" does not require water - a very scarce resource on Mars.

Sulfur-based concrete is not a new idea, and there have been some problems with it. The earthly variety has been found to shrink during the cooling process, creating cavities and weakening the mixture. But the Northwestern scientists discovered that using about 50 percent sulfur and 50 percent Martian soil created a material suited to Martian conditions.

"Given the environmental conditions on Mars - i.e., gravity, atmospheric pressure, temperature range, etc. - it is scientifically sound to produce sulfur-based Martian concrete," Wan told DW. "However, we were a bit surprised by the high sulfur content needed to be mixed with the soil."

The resulting concrete is two times stronger than the typical sulfur-based variety, most likely because sulfur bonds chemically with the minerals found in Martian soil. It is also 100 percent recyclable as sulfur can be melted and reused.

Useful discovery

The project started off as a lunar concrete study. However, Dr. Wan said, the team faced the problem of sulfur's transforming from a solid into a gas in the moon's near-vacuum environment - a process known as sublimation. For this reason the researchers decided that Martian concrete "would be a great alternative."

"Mars has a much higher atmospheric pressure than the moon," Wan said, "and thus sublimation is not an issue there."

Wan believes that the next logical step would be to combine the Martian concrete concept with 3-D printing technologies.

But the execution of this plan is still years away, and in the meantime the study has been submitted for peer review. Despite the initial success, some time will pass before this new concrete receives the full go-ahead.

"Long-term performance of Martian concrete still needs to be studied," Wan said.