Microbes on the Moon
A bathroom mould is not going to spread across the Moon. There is no rain, no breathable air and no stable liquid water on the lunar surface. Yet spores carried from Earth may not die as quickly as that setting suggests.
A NASA-led study published in August 2026 mapped small niches near the lunar south pole where human-associated microbes could remain viable. The most persistent candidate was Aspergillus niger, a darkly pigmented fungus common in warm, damp buildings and repeatedly detected in spacecraft environments, including the International Space Station.
Its advantage was specific. Among the organisms considered, A. niger had the highest measured resistance to ultraviolet radiation, surpassing even Deinococcus radiodurans, a bacterium so resistant to radiation and desiccation that it is routinely used as a benchmark for biological toughness.
The new work did not place living mould on the Moon. It combined existing laboratory survival measurements with detailed models of sunlight, temperature and terrain. What emerged was a map of where dormant microbial cells might endure for days, not where they could grow into a lunar ecosystem.
Survival Models and Lunar Geography
The study in Science Advances was led by planetary scientist Prabal Saxena of NASA’s Goddard Space Flight Center. Its question was practical: if astronauts and spacecraft deliver Earth microbes to the lunar south pole, which patches of ground might fail to kill them immediately?
The team analysed three regions being considered for human exploration: Nobile Rim, Connecting Ridge and De Gerlache Rim. The researchers combined topographic and temperature information from NASA’s Lunar Reconnaissance Orbiter with a model of how solar ultraviolet radiation strikes the surface.
They then brought in survival limits reported by earlier microbiology experiments. Each organism’s tolerance profile was compared with the maximum temperature and accumulated ultraviolet dose predicted for each mapped location. This produced potential survival zones at several spatial scales.
No organism in the study was physically exposed at those lunar sites. The maps are predictions based on remote sensing, illumination modelling and laboratory measurements obtained under particular conditions. Real lunar dust, vacuum, radiation, temperature cycles and the way cells clump or hide inside materials could change the outcome.
Comparing Potential Survivors
The researchers selected organisms associated with humans, indoor spacecraft environments or earlier exposure studies. They included the bacteria Bacillus subtilis, Staphylococcus aureus and Deinococcus radiodurans, along with Aspergillus niger and several species of the fungus Fusarium.
D. radiodurans was the obvious heavyweight. It can repair severe DNA damage and withstand doses of ionising radiation that kill most life. Aggregates of related Deinococcus cells have survived years of exposure outside the ISS, reinforcing the bacterium’s reputation as one of Earth’s most radiation-resistant organisms.
A. niger comes from a more familiar world. It thrives in warm, damp settings such as bathrooms and heating, ventilation and air-conditioning systems. It has been sampled inside the ISS, and earlier experiments found fungal spores capable of surviving beyond the station’s protective walls.
That does not mean the exact spores modelled here were scraped from an orbital wall or a bathroom tile. The study compared species-level resistance information. The connection matters because A. niger is a plausible human or spacecraft stowaway, not because every strain is identical.
Ultraviolet Resistance and Terrain Shadows
The fungus owes much of its durability to its spores. They have thick cell walls, dark pigment and low metabolic activity, all of which help them remain intact through drying and other stresses. Their black colour gives A. niger its name.
In a 2020 laboratory study of space-radiation resistance, researchers exposed wild-type A. niger spores and several mutants to X-rays, helium and iron ions, and UV-C light. The UV-C dose required to inactivate 90 per cent of wild-type spores, known as the LD90, was 1,038 joules per square metre. The corresponding published LD90 used for D. radiodurans was 660 joules per square metre.
The Moon’s axis is tilted by only about 1.5 degrees, so the Sun stays close to the horizon at the poles. Ridges and crater walls cast long shadows. Even small bumps, rocks, rover tracks or boot prints could reduce the direct ultraviolet dose reaching the ground behind them.
To capture that geometry, the researchers used ray tracing, a technique better known for modelling the paths of light in computer graphics. Combined with laser-altimeter topography, it allowed the team to estimate direct and scattered ultraviolet exposure around the candidate south-polar regions.
Implications for Science
Humans shed microbes continuously. Suits, airlocks, habitats, tools and rovers will carry biological material even under careful contamination control. Robotic spacecraft can be baked or treated aggressively, but hardware designed around living crews cannot be sterilised to the same standard.
If cells or biological fragments persist in cold shadows, later instruments might detect material brought from Earth and mistake it for something older. The south pole is scientifically valuable partly because permanently shadowed ice may preserve a record of water, organic chemistry and impacts reaching deep into lunar history.
A living spore can be metabolically quiet. In the study’s context, survival means remaining viable for at least one Earth day, and in some modelled locations up to a week. It does not mean the microbe is active.
The authors want higher-resolution topography and more detailed illumination models. They also see the Moon as a natural laboratory. A carefully documented deposit in a shaded location could test how long selected microbes remain viable under genuine lunar conditions. In a landscape where the Sun scrapes the horizon, the difference between immediate sterilisation and days of suspended survival may be nothing larger than a ridge or a boot print.