May 6, 2026

4 min read

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Could this fungus live on Mars? Maybe it already does

An almost unkillable fungal strain isolated from NASA’s ultrasterile clean rooms hints at “critical gaps” in interplanetary quarantine

By Leonard David edited by Lee Billings

This selfie-style composite image from May 10, 2025 shows NASA’s Perseverance rover on the surface of Mars. Within clean rooms where Perseverance and other spacecraft were tested and assembled, scientists have discovered extremely tough microbes that might survive a voyage to Mars—and even the hostile conditions on the planet’s surface.

NASA/JPL-Caltech/MSSS

The greatest pitfall in the search for extraterrestrial life—according to science fiction, anyway—is foolhardy researchers somehow bringing aliens to Earth to wreak havoc.

But after decades of exploring our seemingly sterile solar system, real-world scientists today are much more concerned with the opposite problem: The possibility that Earth’s life will escape our planet to contaminate other worlds, sabotaging the quest to find any genuine “second genesis” of biology around the sun. Imagine that a multibillion-dollar robotic mission found wriggling microbes on Mars and that follow-up studies then revealing those “aliens” had DNA and other biomolecular machinery that showed they were emigrants from Earth.

Astrobiologically speaking, we would have met the enemy—and it would be us. Taking a cue from sci-fi, you might call such life-forms “Klingons,” for their presumptive hitchhike to the Red Planet as stowaways in spacecraft sent from Earth.

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“Planetary protection” is the term scientists use for efforts to prevent otherworldly invasions of all sorts; to date, most of it has focused on Mars, but the practice applies to all potentially habitable environments within reach of our spacecraft. In the 1970s, for example, NASA did its best to keep its twin Viking landers Klingon-free before launching them to Mars. And if the NASA-led international Mars Sample Return effort ever manages to bring its precious payload back to Earth, the agency will be tasked with quarantining those specimens as if they contain extreme biohazards rather than lifeless bits of rock and soil.

So far, bacteria have been the bogeymen that most planetary protection protocols have been designed to defeat. Now, however, it appears that there’s another type of terrestrial life to be worried about.

A new study has found about two dozen fungal strains isolated from NASA spacecraft assembly clean rooms that are capable of surviving a pretakeoff cleansing of ultraviolet radiation exposure. One in particular—a fungus called Aspergillus calidoustus—proved exceptionally resilient, surviving extended exposures not only to ultraviolet irradiation but also to conditions mimicking the vacuum of space and the surface of Mars. A. calidoustus even withstood the baking at 125 degrees Celsius that NASA now uses to notionally sterilize spacecraft destined for the surface of that world.

The results, published last month in the journal Applied and Environmental Microbiology, suggest that NASA, other space agencies and even private aerospace companies must revise clean room protocols to address nigh-unkillable fungi and bacterial brethren alike. The findings also raise the remote but alarming prospect that previous missions have already exported hardy Earthly microbes to Mars.

An “Entirely Predictable” Critical Gap

The hyper-resilience of A. calidoustus and other fungi represent a “critical gap” in planetary protection strategies, says the study’s lead author Atul Chander, a postdoctoral microbiologist at the University of Mississippi.

The need to close that gap is growing more urgent, thanks to a new generation of ambitious missions that aim to send more landers, rovers and even helicopters to Mars—and beyond. It’s also growing more complicated, thanks to the expanding list of nations—as well as private companies—that are planning interplanetary missions, some of which involve returning extraterrestrial samples to Earth.

This overhead view from November 2019 shows NASA’s Perseverance rover (above center) in the High Bay 1 clean room of the Spacecraft Assembly Facility at NASA’s Jet Propulsion Laboratory.

NASA/JPL-Caltech

Planetary protection policies are coordinated at an international level through the Committee on Space Research (COSPAR), which provides guidelines to support compliance with the United Nations’ Outer Space Treaty of 1967.

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