One of the biggest challenges facing crewed missions to Mars is figuring out how to protect crewmembers from the onslaught of deadly cosmic rays.

Now, scientists at a number of universities say there’s growing evidence that an unusual solution could be effective: building shields out of a radiation-absorbing fungus that grows near the Chernobyl Nuclear Power Plant.

Apart from distance, one of the greatest challenges facing crewed missions to Mars is cosmic radiation. The deadly cosmic rays found outside the Earth’s protective layer pose a significant threat to the health of crew members, making it essential that we figure out how to protect them.

After conducting a small test on the International Space Station, scientists from the John Hopkins University and Stanford found that an extremely thin sample of the fungus Cryptococcus neoformans was able to block and absorb two percent of the cosmic rays that hit it while it was on the ISS.

That’s certainly not enough to protect astronauts, but the sample in question was only two millimeters thick. A layer just 21 centimeters thick, the scientists say, would be enough to keep future Mars settlers safe.

Another interesting thing about the potential solution is that damaged fungus shields would be able to grow back. “What makes the fungus great is that you only need a few grams to start out,” says Stanford researcher and study co-author Nils Averesch. “It self-replicates and self-heals, so even if there’s a solar flare that damages the radiation shield significantly, it will be able to grow back in a few days.”