Earth microbes carried by future astronauts could remain alive in protected pockets near the Moon's south pole for at least one day, according to a NASA-led study published in Science Advances on August 19. The finding raises a practical concern for crewed lunar exploration: organisms released from people, spacesuits or habitats could complicate efforts to identify the Moon's original chemistry and, eventually, signs of life on Mars.
The researchers did not find that microbes can multiply on the Moon. Survival in the study meant remaining viable for at least one Earth day, while the lunar surface still lacks liquid water, an atmosphere and moderate temperatures needed for growth. NASA said human contamination is difficult to avoid because bacteria naturally leave skin and can escape from suits and living quarters, making baseline measurements before crews arrive especially important.
The team compared known heat and ultraviolet tolerances of bacteria and fungi with detailed simulations of Nobile Rim, Connecting Ridge and De Gerlache Rim. Those models combined elevation and temperature observations from NASA's Lunar Reconnaissance Orbiter with calculations of radiation reaching the surface. Because sunlight stays low on the polar horizon, craters, ridges and even small terrain features can create cold shadows that block lethal ultraviolet exposure.
Five kinds of microorganisms associated with people or spaceflight environments were assessed, including Bacillus subtilis, Staphylococcus aureus, Deinococcus radiodurans, Fusarium species and the fungus Aspergillus niger. The models produced possible refuges ranging from broad crater floors to areas as small as a boot print. Aspergillus niger, the most ultraviolet-resistant organism examined, could persist even in some partly illuminated locations, the researchers reported.
The result matters for planetary protection as space agencies prepare for sustained activity around the lunar south pole. Apollo astronauts visited equatorial sites, but polar terrain combines long shadows that may preserve water and fragile molecules with sunlit ridges attractive for power generation. NASA researchers said samples should be characterized before human visits alter them, so scientists can separate native lunar material from biological traces delivered from Earth.
The authors also see an opportunity to use carefully monitored lunar sites as natural laboratories for testing microbial endurance under conditions that are hard to reproduce on Earth. Their next challenge is to measure what astronauts and hardware carry, establish contamination controls and test the models on the surface. The work does not suggest an inhabited Moon; it shows that dormant terrestrial cells may last long enough to affect how future discoveries are interpreted.
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