Microbes may make it on the Moon

This scanning electron micrograph reveals a closeup look at the spore-bearing head of Aspergillus niger — commonly referred to as black mold. The toughest of the five human-associated microbes tested in a new study, this mold proved most likely to survive for a week or longer in the shadowed terrain near the Moon's poles. Credit: Mogana Das Murtey and Patchamuthu Ramasamy, via Wikimedia Commons, CC BY-SA 3.0 According to a new study, bacteria and fungi shed by humans could survive on the lunar surface for up to a week or longer. The study, published in Science Advances Aug. 19, paired microbiologists with researchers who model lunar surface conditions. Led by Prabal Saxena, research space scientist at Goddard Space Flight Center, the team mapped where five common microbes could withstand the ultraviolet (UV) radiation near the Moon’s poles. The researchers expected surviving microbes, if there were any, to cluster near the permanently shadowed regions that never see sunlight. Instead, they found survivable pockets spread across the entirety of the polar regions. The results suggest that future astronauts conducting science and collecting samples in those regions will have to be more cautious than previously expected when accounting for possible contamination from microbes carried with them from Earth. “[W]e were actually very surprised when we mapped the lunar poles,” Stefano Bertone, co-author and University of Maryland associate research scientist, tells Astronomy, “to see that … there are very large regions — even far away from the permanently shadowed regions — where at least one of the species we analyzed can survive for several hours to several days.” Why the poles? It might seem strange to worry that astronauts could be shedding microbes as they explore the Moon in their air-tight spacesuits. However, Bertone explains, spacesuits are not completely sealed: They vent the astronauts’ breath, which can cause microbes from Earth to be littered across the surface of the Moon as astronauts move about. The paper notes another leak point, too. Airlocks, which spacecraft use to move people and equipment between their sealed interiors and the vacuum outside, are also a likely source of venting. Any microbes shed inside the spacecraft could potentially escape through the airlock. As Bertone puts it, “decontamination procedures of anything are not perfect.” Despite best efforts to mitigate contamination, some amount of microbe shedding is inevitable. When the Apollo astronauts walked on the Moon between 1969 and 1972, they landed close to the lunar equator, and, without knowing it, in one of the most hostile spots on the surface for the microbes riding along. The Sun climbs high overhead there, casting very few shadows to block its UV radiation — the biggest threat to microbes. Earlier studies have suggested that any microbes those astronauts left stood almost no chance of survival. But the Artemis program is headed somewhere different. NASA’s return to the Moon, along with its plans for a permanent lunar base, targets the south pole — chosen largely for the water ice locked away in its permanently shadowed regions, in craters so deep the Sun never reaches their floors. It’s that same geography that also makes the south pole a friendlier place for microbes. Because the Moon tilts only slightly on its axis, the Sun never climbs far above the horizon at the poles, meaning they receive lower levels of UV radiation than the equator. And the smallest surface bumps and crater rims still can throw shadows that — even if they aren’t deep enough to harbor ice — can shelter microbes. If you’re going to investigate whether microbes can survive on the lunar surface, the poles are an obvious candidate, both for their relatively hospitable environment and the fact that humans might soon set foot there. RELATED: Why NASA is targeting the Moon’s south pole for Artemis Purple splotches across the Moon’s north and south poles (top) mark how much ultraviolet radiation reaches the surface over a single lunar day — the darker the shade, the lower the dose of UV. Below, the same terrain is colored to indicate microbe survivability. Lavender marks ground where only the toughest of five tested microbes, the fungus Aspergillus, can survive. Red, yellow, blue, and orange patches in the insets show spots hospitable enough for multiple species. White squares mark candidate landing regions for NASA’s Artemis missions — revealing that the areas astronauts will be exploring and the areas where microbes can survive are very often one and the same. Credit: Saxena et al., Sci. Adv. 12, eaec0811 (2026) Mapping microbes Bertone and his team didn’t send microbe samples to the Moon to see if they survived. Instead, they combined two existing datasets and modeled survivability. Crucially, they also accounted for something earlier models had ignored: the shape of the ground itself. The five organisms Bertone’s team chose were common and hardy — the kind of microbes both known to be carried by humans and particularly hard to kill. Three are bacteria: Bacillus, Staphylococcus, and Deinococcus. Two are fungi: Aspergillus and Fusarium. “We selected them because they’re usually found around humans,” Bertone tells Astronomy. “We carry a lot of them on us. … Some of them have been observed on the International Space Station, so they’re known to be pretty hardy.” The team’s microbiologists started with published research on how much UV radiation and heat it takes to kill off the selected bacteria and fungi. The lack of air and the extreme low temperatures of the Moon were not a factor; microbes can sit in a vacuum for months without dying, and freezing is a common way to preserve them on Earth. The team then calculated a “survivability threshold” for each microbe — effectively the UV dose and amount of heat that would wipe it out. From there, the team needed to know where on the Moon’s surface UV radiation and temperature would rise above those thresholds. Earlier models had estimated this using latitude alone, treating the Moon as essentially flat — an approach that didn’t account for how dramatically topography and shadows can alter UV flux near the poles. That’s where the planetary scientists came in. Working from the Lunar Reconnaissance Orbiter’s laser altimeter elevation data, temperature readings from its Diviner instrument, and models tracing how sunlight reflects across the terrain throughout the Moon’s seasons, they built 3D maps capturing the so-called “UV flux” at every point on the surface. This time, the maps accounted for the terrain’s real shape. The poles turned out to be cool enough, even at their warmest, to not threaten the microbes in any of the regions, making UV the only remaining threat. The researchers worked in two passes: a broad first look across both poles using a simplified model with UV flux determined at roughly 60 meters (or around 200 feet) per pixel, followed by a much finer analysis zoomed into three candidate Artemis landing regions. In those regions they used ray tracing (tracing the path of sunlight, ray by ray, as it travels from Sun to the surface, accounting for every object that blocks or bounces the light) to capture the UV flux of the terrain in increased detail down to 5 meters (approximately 16.5 feet) per pixel. The last step was laying one dataset over the other. Everywhere the modeled UV flux stayed under a microbe’s threshold, that microbe could theoretically survive; everywhere it didn’t, the microbe couldn’t. When that comparison was run for all five microbes, across multiple regions, stretches of time, and seasons, the result was a set of maps, colored patchworks showing exactly where, and for how long, each organism could survive. Surprising results The process for producing those maps carried an element of surprise. Bertone would receive the data from the microbiologists, and run the model in software on his computer. “I get a file as output [from] my software,” he explains, “and then I need to put it in some GIS mapping visualization tool.” Finally, he would open the output in the GIS tool and set the colors. Only then would the results materialize for the first time. Much to Bertone’s surprise, the first map came back covered in color. The team had expected small pockets of survivability — a smear of color hugging the rims of the permanently shadowed craters, maybe, and not much else. “So much for ‘nothing can survive on the Moon,'” Bertone said in a press release. Wide stretches of the lunar poles, far beyond the shadowed craters, turned out to be survivable for at least one of the five microbes. Bertone’s first instinct was doubt, not celebration. He went back through the numbers, checking the UV flux against the lethal doses the microbiologists had supplied, looking for a mistake. There wasn’t one. Staphylococcus and Bacillus fared worst, confined to the smallest slivers of terrain mostly along crater rims. Deinococcus and Fusarium did somewhat better, with their survivability range burgeoning out slightly farther. But each of these four microbes was limited to areas where topography offered some protection from high UV doses. On map after map, the fungus Aspergillus outlasted all of them — surviving across roughly 2 to 9% of sunlit terrain in summer and 15 to 30% in winter, with pockets in every region the team studied holding out for a week or longer. Even inside the permanently shadowed craters, where scattered light barely trickles in, the other four microbes could hang on in only limited spots, but Aspergillus survived widely. The team attributed Aspergillus’s widespread survivability to its high UV tolerance. Relative to the bacteria studied, Aspergillus can tolerate anywhere from 13 to over 100 times more cumulative UV exposure before dying off. Relative to Fusarium, the other fungus in the study, it can tolerate roughly nine times more. Because Aspergillus’s survivability threshold sits so far above the other species, it stays alive across a much wider swath of the polar regions, surviving not just near the deepest shadows but in more well-lit patches the other four microbes can’t handle. Looking ahead The findings have big implications for future missions to the Moon and beyond. For example, Bertone imagines an astronaut two hours into a traverse near the lunar south pole, walking back over ground they crossed earlier that morning to collect a sample. Thanks to the team’s findings, the astronaut will have serious considerations: “If I followed this path two hours ago, and now, going back, I collect a sample — can I be sure that this sample is not contaminated by what I did? … Should I maybe wait a bit longer, or take a slightly different path?” Bertone explains. Bertone says the research isn’t necessarily prescriptive, telling astronauts what to do to minimize their impact, but that it should help inform how decisions are made moving forward. “[A]t this level, it’s really to make people aware of the context of the potential problem — the potential contamination.” That awareness will matter more as human exploration moves past the Moon. Scientists have long eyed Mars as a place that might once have supported life of its own. “[W]hen we go to Mars to search for signs of life beyond our planet, we will want to make sure it’s not stuff we brought,” Saxena said in a press release. Confusing an ancient martian microbe with a modern human stowaway would be a costly mistake, one this kind of survivability mapping could help prevent. But Bertone is careful not to stretch this particular study too far. Mars has an atmosphere, and its greater distance from the Sun likely means lower UV flux than the Moon sees — different variables entirely, requiring their own model. “We haven’t studied, analyzed what this would mean at Mars,” he says. “It’s a good follow-up work … it’s certainly something to check.” RELATED: Hardy desert moss might survive on Mars Bertone says he and his colleagues are working on extending the analysis to every Artemis candidate landing region, using a newly released set of higher-resolution topographic maps and more detailed modeling of how UV radiation shifts over time. The team is also planning new lab experiments, aiming to test these microbes and others under more controlled conditions to pin down more precisely how long each one can survive. Brooks Mendenhall is a staff writer at Astronomy, based in Chattanooga, Tennessee, fueled by an unending curiosity about the universe. A former classroom teacher, he has a knack for breaking down complex concepts for a wide audience.