NASA follows international guidelines called the Planetary Protection protocol, aimed at making sure Earth’s biology doesn’t taint celestial bodies, and vice versa. The agency also has a dedicated team, the Jet Propulsion Laboratory’s biotechnology and planetary protection group, or B.P.P.G., that oversees efforts to avoid cross-contamination on missions.
Several scientists behind the new research, including the study’s leader, Kasthuri Venkateswaran, a former senior scientist at the Jet Propulsion Laboratory, have worked in the protection group, so they knew firsthand that hardy microbes existed. Still, Dr. Venkateswaran called the fungal strain’s survival “remarkable.”
Previous studies have identified various bacteria and fungi on NASA facility surfaces, including the ultrafiltered clean rooms, where spacecraft are constructed and tested. There, employees involved in assembly wear full-body coveralls and masks, but decontamination techniques are currently focused on eliminating bacteria, not fungi.
In the study, researchers examined 27 fungal strains they had acquired from the floors of NASA clean rooms used in the Mars 2020 mission, which landed the Perseverance rover on Mars, plus two control microbes known to tolerate radiation well. Most of the samples that survived a preliminary ultraviolet screening and underwent more intense treatments died quickly, but the A. calidoustus, which had been taken from a Florida assembly facility, endured.
The scientists subjected the A. calidoustus spores to six months of chronic neutron radiation — mimicking space travel — and almost half of them survived. They heated them with 125 degree Celsius dry heat, typically used to sterilize spacecraft components, and the spores outlasted even Bacillus pumilus, a species that NASA often uses as a benchmark. And they treated the spores with harsh conditions that mirrored the experience on Mars itself: 24 hours of extreme UV radiation, plus low atmospheric pressure and the average annual Mars surface temperature of negative 60 degrees Celsius.
