Credit: NASAThe next astronauts to walk near the Moon’s south pole will bring drills, rovers, spacesuits—and an unavoidable piece of Earth.
In some of these spots, Earth bacteria and fungi could remain alive for days, weeks, or potentially longer.
Surviving for some time, even if we’re talking about months, does not mean the microbes could colonize the Moon.
Credit: Wikimedia CommonsThat problem is particularly urgent because scientists value the lunar poles precisely for what they may have preserved.
Scientists might characterize a site before astronauts arrive, record which microbes a mission brings, and return months or years later.
The dark side of the moon from NASA’s Artemis II mission. Credit: NASA
The next astronauts to walk near the Moon’s south pole will bring drills, rovers, spacesuits—and an unavoidable piece of Earth.
Bacteria live on our skin and inside our bodies. Fungi settle into spacecraft and ventilation systems. Some of those organisms will almost certainly escape through airlocks, cling to equipment or shed from spacesuits onto the lunar surface.
Scientists have long assumed the Moon would quickly destroy most microbial stowaways. After all, it’s barren, lifeless rock for a reason. But a new NASA-led study is here to say: “Not so fast…”
Near the poles, craters and other terrain create patches of permanent or prolonged shadow, shielding microbes from the Sun’s lethal ultraviolet radiation. In some of these spots, Earth bacteria and fungi could remain alive for days, weeks, or potentially longer.
Now that’s a problem. Contamination could make it harder to distinguish pristine lunar chemistry from material humans introduced. Yet if biological contamination cannot be eliminated, researchers argue that carefully tracking it could turn the Moon into an extraordinary experiment in how life survives beyond Earth.
“Humans are natural explorers, and with them come their voices, their memories … and their microbes,” said Prabal Saxena, a planetary scientist at NASA’s Goddard Space Flight Center and the study’s lead author.
“For some scientists, myself included, that reality can be unsettling. But it also creates an opportunity to turn an imperfect situation into a useful experiment.”
The Moon’s Microbial Hiding Spots
Black mold growing on the International Space Station. Of course it had to be black mold. Credit: NASA
Saxena and his colleagues combined laboratory measurements of microbial resistance with maps of temperature and sunlight around the lunar poles made with NASA’s Lunar Reconnaissance Orbiter.
They focused on five organisms likely to accompany humans into space: Bacillus subtilis, Staphylococcus aureus, the famously radiation-resistant Deinococcus radiodurans, several species of Fusarium fungi, and Aspergillus niger, a common fungus already found in bathrooms, HVAC systems, and even aboard the International Space Station.
The Moon’s poles offer very different conditions from the equatorial sites visited during Apollo. Because the Sun sits extremely low on the horizon there, crater walls and ridges cast long shadows. Some crater floors never receive direct sunlight at all.
Such shadowy regions can become extraordinarily cold, but cold itself is not necessarily lethal to microbes. Freeze-drying is routinely used on Earth to preserve microorganisms. Over the short periods studied here, ultraviolet radiation appears to be a more effective killer than either vacuum or low temperature. So shade is support important for any microbe that might survive on the moon for any meaningful amount of time.
(A) Microbial survivability map showing which species can survive at least 1 day within the PSR when accounting for scattered UV light. (B) Aspergillus survival duration map showing survival time in days within the PSR. Credit: Science Advances
The researchers modeled Nobile Rim, Connecting Ridge and De Gerlache Rim, regions relevant to future south-polar exploration. The standout survivor was Aspergillus niger. Outside permanently shadowed regions, conditions suitable for its survival covered roughly 2 to 9% of the mapped terrain during lunar summer and 15 to 30% in winter. About 3% of each region could allow it to persist for at least seven Earth days.
Inside permanently shadowed areas, all five microbes had some potential refuges lasting more than a week. Earlier research published in Astrobiology in 2025 had already suggested that some lunar permanent shadows may be unusually poor at sterilizing terrestrial microbes. The new study broadens that picture by examining several human-associated organisms and more detailed terrain.
Let’s get something clear first. Surviving for some time, even if we’re talking about months, does not mean the microbes could colonize the Moon. The researchers found no evidence they could grow or reproduce there. Stable liquid water, among other essentials, is missing.
But even dormant or dead cells can be consequential. Their proteins and other organic molecules could remain in lunar samples for years and confuse future measurements.
Contamination Hazard?
Buzz Aldrin’s footprint—potential future microbial shelter. Credit: Wikimedia Commons
That problem is particularly urgent because scientists value the lunar poles precisely for what they may have preserved.
Permanently shadowed craters contain water ice and other volatile compounds that could preserve clues about material delivered by comets, asteroids and the solar wind. Human activity will add a new chemical layer to that archive, which will later have to be disentangled from lab results.
“Contamination is unavoidable, so we need to track what we’re bringing with us so that we can later distinguish lunar chemistry from stuff we brought from Earth,” study co-author Heather Graham told Reuters.
Humans may also create new microbial shelters themselves. At extreme polar latitudes, the Sun is so low that boot prints, rover tracks and small excavations could form shadowed depressions, the authors note.
The researchers argue that these microbial hiding places do not necessarily need to be left untouched. Scientists could return to them again and again to see what survives over time.
Scientists might characterize a site before astronauts arrive, record which microbes a mission brings, and return months or years later. Which species disappear? Which remain? Does burial beneath lunar soil prolong survival? How much difference does permanent shadow make?
The lesson could become even more important on Mars, where conditions are considerably more favorable to terrestrial microbes and where scientists hope to search for evidence of past (or, who knows, present) indigenous life.
The Moon could become a real-world test of a small piece of panspermia: can microbes survive the trip between worlds and persist after they arrive? Tracking what lasts, where, and for how long could offer rare clues about how life might spread through space.
The study was published in the journal Science Advances.
