BELLEVUE, WASHINGTON – Like anyone who has ever had a mold attack, the fungi can be very hard to kill. It has been found that molds are also very resistant to the harsh conditions in space. Its spores can survive radiation doses 200 times higher than those that would kill a human, researchers reported today at the Astrobiology Science Conference. Such hardiness in winter could make it difficult to eliminate the health risks of mold for astronauts. Molds could someday also threaten other parts of the solar system – hitching mold spores from Earth.
Astronauts on the International Space Station (ISS) are already constantly struggling with mold growing on the walls and equipment of the station. Of course, this shape is in a protected structure in a near-Earth orbit where the radiation doses are low. Outside the station, the cans are higher – and they would be even higher on the hull of a spacecraft going to or beyond Mars.
Marta Cortesão, microbiologist at the German Aerospace Center (DLR) in Cologne, Germany, and colleagues sprayed X-rays and heavy ions on a black fungus abundant in the ISS called Aspergillus niger . According to Cortesão, the researchers have fired "stupid amounts" of radiation – much more than on a Mars spacecraft (0.6 gray per year) or on the surface of Mars (0.2 gray per year). The gray is a measure of the amount of absorbed radiation energy.
The researchers found that the spores could survive radiation doses of 500 to 1000 gray depending on the type of radiation they were exposed to. In contrast, people dying of doses of 0.5 Gray develop radiation sickness and are killed by 5 Gray. Cortesão also found that the spores survived large amounts of high-energy ultraviolet radiation, which is commonly used as a hospital disinfectant and has been proposed for the sterilization of spacecraft surfaces.
Cortesão warns that her research focused only on radiation and did not consider all aspects of the harsh space environment. However, at least one older study suggests that mold spores in vacuum are even more resistant to radiation. One thing is certain now, she says: "We will certainly have spurs on our space travel. Mushrooms have been forgotten for 20 or 30 years, but it is time to return to them.
Andrew Schuerger, microbiologist and Mars astrobiologist at the University of Florida at North Merritt Island, agrees. So far, the focus of efforts to protect Earth's microorganisms from contaminating other worlds has been bacterial, as most microorganisms on the surface of spacecraft have been bacterial. "I really like a presentation like this [that says]. Let's not forget this other group of microorganisms called mushrooms," he says astrobiologist at New Mexico State University in Las Cruces.
One of the mysteries in the study of the origin of life is that at the beginning of its history, the Earth appears to have transitioned from the prebiotic to a rather complex microorganism. Some scientists believe that more time was needed than had passed since the planet began became habitable for the first time. One idea, Mason says, is that life originated elsewhere, either in our solar system or farther away. "Now that we know that life on Earth can survive in space, it's certainly reasonable to believe that it could have come to Earth from elsewhere," he says.