Resilient Fungi in Spacecraft Clean Rooms Challenge Mars Planetary Protection

A recent study published in *Applied and Environmental Microbiology* identified 23 fungal strains isolated from NASA spacecraft-assembly clean rooms that survive a pre-launch ultraviolet (UV) decontamination step. One strain, the fungus *Aspergillus calidoustus*, withstood prolonged UV exposure, simulated vacuum, and the 125 °C baking protocol currently used to sterilize hardware destined for the Martian surface. The authors describe the organism’s ability to endure conditions that mimic the harsh environment of Mars, highlighting a “critical gap” in existing planetary-protection strategies.

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“Planetary protection” refers to efforts that prevent forward contamination of extraterrestrial bodies. Since the 1970s, NASA has applied stringent bacterial-spore reduction measures to missions such as the Viking landers. Internationally, the Committee on Space Research (COSPAR) issues guidelines that support compliance with the United Nations Outer Space Treaty of 1967. These guidelines are intended for all space-faring nations, not a single country.

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The study’s lead author, postdoctoral microbiologist Atul Chander of the University of Mississippi, coordinated the work with NASA’s Jet Propulsion Laboratory (JPL). Moogega Cooper, a planetary-protection engineer at JPL, oversees NASA’s COSPAR-compliant procedures. Nick Benardini, NASA’s planetary-protection officer in Washington, D.C., is directing the development of new metagenomic tools. Former planetary-protection officer Cassie Conley (2006-2017) provided critical commentary on the findings. COSPAR’s Panel on Planetary Protection and signatory space agencies are also implicated in revising standards.

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• 23 fungal isolates recovered from clean-room surfaces.

Outward Bound – The Issue of Planetary Protection by Earthly Critters

• *A. calidoustus* survived extended UV irradiation, vacuum conditions, and 125 °C heat treatment.

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• The study suggests that current bacterial-focused assays may miss similarly robust fungal taxa.

Outward Bound – The Issue of Planetary Protection by Earthly Critters

NASA maintains a suite of COSPAR-aligned handbooks, training courses, and assay protocols, according to Moogega Cooper. Nick Benardini notes that emerging tools will incorporate “metagenomics”—the assessment of microbial communities directly in their natural environments—to improve monitoring of clean-room microbiomes. COSPAR’s guidelines, as highlighted by Chander, are designed for universal adoption by all signatory nations and private entities operating under national flags.

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Cassie Conley argues that the longstanding emphasis on bacterial spores reflects an assumption that Martian conditions would be sterilizing, a view she calls “only by people who wished that Mars conditions would be sterilizing.” She stresses that the unknown capabilities of Earth life demand broader protective measures.

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The authors caution that, while the resilience of these fungi raises the “remote but alarming prospect” that earlier missions may have unintentionally delivered hardy microbes to Mars, no direct detection of such organisms on the planet has been reported. The extent to which current decontamination practices mitigate this risk remains uncertain.

Scientific American

• “Planetary protection” is the term scientists use for efforts to prevent otherworldly invasions of all sorts. — *Scientific American* article (definition)

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• “These guidelines are not specific to any single country but are intended to be followed by all spacefaring nations,” — Atul Chander

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• “critical gap” — Atul Chander (describing fungal resilience)

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• “The whole point [is] that we don’t know all the capabilities of life on Earth—and shouldn’t pretend we do,” — Cassie Conley

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• “metagenomics”—the assessment of communities of microbial organisms directly in their natural environments. — Nick Benardini

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NASA is expanding support for the commercial sector by developing metagenomic mapping tools to track clean-room microbiomes. These efforts aim to integrate fungal monitoring into planetary-protection protocols ahead of upcoming Mars Sample Return missions and prospective human expeditions, thereby addressing the identified gap before further interplanetary travel.

Scientific American