This Microscopic Fungus Survived NASA’s Sterilization Protocols—and Is Hardy Enough to Potentially Contaminate Mars

The microbe was gathered from the agency’s clean rooms, where experts build spacecraft in carefully controlled environments. The findings reveal gaps in the agency’s procedures to prevent durable hitchhikers

May 13, 2026 2:57 p.m.

A NASA cleanroom as seen from an elevated point of view with lots of equipment — A shell that protected the Perseverance rover during its descent to Mars in a clean room at NASA's Jet Propulsion Laboratory NASA / JPL-Caltech

As scientists search for life beyond Earth, spacecraft need to avoid accidentally bringing organisms from our home planet to other celestial bodies. It would be unfortunate to discover that an “alien” life form was simply a hitchhiker.

That’s why NASA and other countries’ space agencies follow “planetary protection” protocols, which call for sterilization and other measures to curb potential contamination. They mostly focus on getting rid of Earthly bacteria.

However, some microbes might be slipping through the cleaning cracks. In a study published April 20 in the journal Applied and Environmental Microbiology, researchers found that a fungus called Aspergillus calidoustus—collected from some of NASA’s clean rooms—could endure simulated conditions associated with space travel and Mars. The findings hint that the agency needs to update its planetary protection procedures.

“This is really about doing exploration responsibly,” study co-author Atul M. Chander, a microbiologist at the University of Mississippi, tells the New York Times’ Emily Baumgaertner Nunn. “As we explore this universe, we want to be able to send aircraft without bringing any hardy Earth microbes.”

Fun fact: A bacterium’s resilience supports a curious hypothesis about Earthly life’s origins

In a study published earlier this year, researchers found that Deinococcus radiodurans—an extremophile that lives in Chile’s high-altitude deserts—could probably survive the immense pressure of being ejected from Mars. The findings support the plausibility of the lithopanspermia hypothesis, which posits that rocky debris expelled from planets during impacts could ferry microbes to other worlds—including Earth.

NASA’s clean rooms are where experts assemble spacecraft hardware like rovers and landers. The areas are specially designed to control particulate, molecular and biological contamination.

To search for potential hitchhikers—particularly those that could reach Mars, where researchers are racing to find signs of ancient microbial life—Chander and his colleagues gathered samples from clean rooms at the Kennedy Space Center in Florida and the Jet Propulsion Lab in California. They identified 27 fungal strains from assembly facilities used during the Mars 2020 mission, which got the Perseverance rover to the Red Planet.

Exposing the fungi to conditions mimicking those of space revealed the extreme resilience of A. calidoustus, specifically its reproductive spores. Nearly half of the tested spores survived six months of high radiation, similar to what they’d experience during space travel. They also fared well after two hours of dry heat at 257 degrees Fahrenheit, a procedure often used to sterilize spacecraft parts. Creating Mars-like conditions—with its dirt, low atmospheric pressure, frigid temperatures and high solar radiation—also proved the fungus’s hardiness.

In the end, the spores succumbed only to the combination of severe cold and high radiation.

The results didn’t surprise Cassie Conley, a plant biologist and former NASA planetary protection officer who wasn’t involved in the study. “The whole point [is] that we don’t know all the capabilities of life on Earth—and shouldn’t pretend we do,” she tells Scientific American’s Leonard David. “Most extremophile biologists who spend two seconds thinking about it would be pretty sure that Earth organisms able to survive on Mars do exist.”

Study co-author Kasthuri Venkateswaran, a former microbiologist at NASA’s Jet Propulsion Laboratory, points out that the results don’t mean that Earthly fungi have made their way to Mars. The findings will, however, help experts better understand microbial resilience, he says in a statement.

“Together, these investigations help refine NASA’s planetary protection strategies and microbial risk assessment approaches for current and future space exploration missions,” he adds.

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