- The researchers recently sent the mold growing at the Chernobyl nuclear fusion site to the International Space Station for study.
- Mold appears to be fueled by radiation, so early research suggests it might help protect astronauts from dangerous space radioactivity.
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Astronauts are at high risk in space, but exposing yourself to dangerous radiation is one of the greatest. On the International Space Station, astronauts are exposed to up to 160 millisieverts of radiation during a six-month mission, according to NASA, that is, about 1,600 chest x-rays, and 26 times more than what the average American citizen receives. Mars is even worse; an astronaut making an 18-month round trip to the red planet would be exposed to 1,000 millisieverts of radiation, or the value of 10,000 chest x-rays.
For protection, astronauts generally rely on radiation shields made of plastics or metals such as aluminum and stainless steel. But these can be heavy and vulnerable to damage.
So in 2018, some high school students from Durham County, North Carolina came up with an unusual solution to this problem: making a moldy shield.
Specifically, they suggested cladosporium sphaerospermum, an organism that appears to feed on nuclear radiation in the same way that most plants feed on sunlight. Mold has thrived in the Chernobyl Exclusion Zone, the 1986 nuclear meltdown site, which remains one of the most radioactive locations on Earth.
The students, led by Graham Shunk, now an incoming sophomore at the North Carolina School of Science and Mathematics, obtained samples of mold species from a company in Minnesota. With the help of research company Space Tango, they were launched into outer space in December 2018.
On the International Space Station, astronauts put mold samples on Petri dishes, leaving one side of each plate empty. Geiger counters then measured radiation levels under the dishes every 110 seconds for 30 days. The results showed that the radiation levels decreased at the height of mold growth: the counters measured a 2.4% decrease in the average radiation levels below the moldy sides.
The preliminary findings from that experiment were uploaded to the bioRxiv research archive on July 17, but have not yet been peer-reviewed. Still, they suggest that the mold could act as a shield against radiation in space.
This is because mold seems to absorb radiation and convert it to chemical energy in a process called radiosynthesis. It is similar to photosynthesis, the process most plants use to convert sunlight into energy.
Shunk and the other researchers suggested that if the mold were about 21 centimeters thick, it could provide humans with adequate protection against radiation levels on Mars. They think that the protection would be stronger if the mold surrounded an object completely, instead of protecting only one side as it did in the studio.
The researchers also noted that mold has a great advantage over other types of radiation shields, as it can grow and replenish in space. That means that a microscopic amount of C. sphaerospermum might be all that is needed at the start of a launch, so it would not add additional weight to a rocket. That could change the game, as NASA estimates that launching something into space costs around $ 10,000 per pound.