NASA scientists say some microbes carried into space by human explorers may be able to survive in sheltered, shadowed areas near the Moon’s South Pole.
The findings, published on Aug. 19, 2026, in Science Advances, underscore the importance of understanding how long Earth microbes can persist in extreme lunar environments. As people establish a more permanent presence on the Moon, contamination from astronauts could make it harder for scientists to separate ancient lunar chemistry from material introduced by humans. Researchers say the same issue will matter when missions eventually search for signs of life on Mars.
“Humans are natural explorers, and with them come their voices, their memories … and their microbes,” said Prabal Saxena, a planetary scientist who led the study from NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “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.”
Microbial Hitchhikers Are Unavoidable
Humans inevitably carry microbes with them. On average, about 1 million bacteria live on every patch of skin roughly the size of a pencil eraser. Some of these organisms can escape from spacesuits and habitats into the surrounding environment.
That creates a challenge for scientists hoping to study chemical evidence connected to the Moon’s ancient geology or possible biology. At the same time, the researchers argue that the Moon could serve as a valuable natural laboratory. Carefully monitored shadowed regions near the South Pole could allow scientists to test the real limits of microbial survival under conditions that are extremely difficult to reproduce on Earth.
Before those experiments can begin, however, researchers need to establish a clear baseline showing what contaminants humans introduce.
“We need to understand what was there before us, because when 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,” said Andrew Needham, a NASA Goddard-based paper co-author who is an Artemis contamination-control scientist for lunar samples.
Some Microbes Are Surprisingly Tough
Even rigorous sterilization cannot eliminate every hardy organism. One example is Aspergillus niger, a fungus that commonly grows in warm, humid environments such as bathrooms and heating, ventilation, and air conditioning systems.
Astronauts have collected samples of the fungus aboard the International Space Station, and previous experiments have shown that it can also survive outside the station. Aspergillus niger was one of five microbes examined in the new study because of its demonstrated resilience in spaceflight conditions.
Scientists were surprised that microbes like these could endure exposure on the exterior of the space station. According to Aaron Regberg, a geomicrobiologist at NASA’s Johnson Space Center in Houston, these organisms are not usually classified as “extremophiles” capable of surviving conditions such as the vacuum of space.
“I would have expected these microbes to have dried out,” said Regberg, who studies space station bacteria and was a co-author on the paper.
NASA can reduce biological contamination on robotic spacecraft by heating them to more than 400 degrees Fahrenheit. That approach is not possible for crewed missions, which means microbial contamination becomes a much more complicated issue when astronauts explore the Moon’s south polar region.
Why Lunar Shadows Matter
To determine where microbes might survive, researchers first examined the unusual way sunlight reaches the lunar poles. In this study, survival means that a microbe remains alive for at least one Earth day. It does not mean the organism is able to grow or reproduce.
Because the Moon has only a slight axial tilt, the Sun appears to stay very close to the horizon when viewed from the poles. Its light sweeps across the surface almost like a flashlight lying flat on a table.
That low angle means crater rims, mountains, ridges, and even small surface bumps can block sunlight from reaching lower terrain. The result is a patchwork of shadowed areas that can stay extremely cold, preserve water, and protect delicate molecules and potential microorganisms from damaging radiation.
Testing Microbes at the Lunar South Pole
Using that environment as a guide, the researchers examined which Earth microbes could potentially withstand conditions near the Moon’s South Pole.
They selected organisms found in spaceflight settings as well as microbes commonly associated with humans. In addition to Aspergillus niger, the group included Bacillus subtilis, Staphylococcus aureus, Deinococcus radiodurans, and several species of Fusarium.
Drawing on an analysis of earlier research, the team determined how much heat and ultraviolet (UV) radiation each organism could tolerate.
The scientists then modeled conditions in three locations near the lunar South Pole — Nobile Rim, Connecting Ridge, and De Gerlache Rim. The simulations relied on detailed maps of elevation and temperature generated from data collected by instruments aboard NASA’s Lunar Reconnaissance Orbiter, along with models showing how radiation reaches the lunar surface.
Microbial Refuges as Small as a Boot Print
The resulting maps identified “survivable niches” ranging from crater floors several miles across to areas no larger than an astronaut’s boot print.
Aspergillus niger proved especially resilient. Because it was the most resistant to UV radiation, the fungus could potentially survive even in locations exposed to some sunlight. UV radiation is deadly enough to many microorganisms that hospitals routinely use it for sterilization.
“When we think of the Moon, we don’t typically think of biology,” said Heather Graham, a paper co-author at NASA Goddard who helps develop tools and techniques for detecting biology that may look nothing like Earth’s. “But the Moon is a place where a cell can survive, so our first exploration of these sites should pay extra attention to our microbial hitchhikers and work hard to characterize lunar chemistry before our visits change what we will find.”
The researchers emphasize that surviving is not the same as thriving. Some microbes may remain dormant in protected regions near the South Pole and potentially complicate future scientific studies, but there is no evidence that the Moon provides the conditions needed for them to grow and reproduce.
Among the missing ingredients is liquid water, which generally depends on the presence of an atmosphere and moderate temperatures.