Mold spores commonly found aboard the International Space Station (ISS) turn out to be radiation resistant enough to survive 200 times the X-ray dose needed to kill a human being. Based on experiments by a team of researchers led by Marta Cortesao, a microbiologist at the German Aerospace Center (DLR) in Cologne, the new study indicates that sterilizing interplanetary spacecraft may be much more difficult than previously thought. New Atlas reports: The researchers exposed samples of Aspergillus and Pennicillium spores to X-rays, heavy ions, and high-frequency ultraviolet light of the kinds and intensities found in space. Such radiation damages DNA and breaks down cell structures, but the spores survived X-rays up to 1,000 gray, heavy ions at 500 gray, and UV rays up to 3,000 joules per meter squared. Gray is a measurement of radiation exposure based on the absorption of one joule of radiation energy per kilogram of matter. To place the results into perspective, five gray will kill a person and 0.7 gray is how much radiation the crew of a Mars mission would receive on a 180-day mission.
Since mold spores can already survive heat, cold, chemicals, and drying out, being able to take on radiation as well poses new challenges. It means that not only will manned missions have to put a lot of effort into keeping the ship clean and healthy, it also means that unmanned planetary missions, which must be free of terrestrial organisms to prevent contaminating other worlds, will be harder to sterilize. But according to Cortesao there is a positive side to this resiliency. Since fungal spores are hard to kill, they’d be easier to carry along and grow under controlled conditions in space, so they can be used as raw materials or act as biological factories.