The Moon is airless, radiation-drenched and can swing from about minus 173 to plus 127 degrees Celsius, yet NASA-led modelling found that some common Earth fungi and bacteria—from human skin, soil and damp bathrooms—could survive dormant for weeks or even months in cold, shaded niches near the lunar poles.

The Moon appears to offer Earth microbes nowhere to hide. It has almost no atmosphere, no stable liquid water on its surface and no shield against ultraviolet light or energetic radiation. NASA’s standard lunar figures put a surface in full sunlight near 127 degrees Celsius and one in darkness near minus 173 degrees.

Now a NASA-led modelling study has found a loophole in that hostility. Near the lunar south pole, cold shadows can remove two of the fastest short-term killers, intense ultraviolet exposure and heat. Hardy fungi and bacteria deposited by astronauts or spacecraft might then remain dormant and viable for days, weeks or, under especially favourable assumptions, months.

That is not evidence of a lunar ecosystem. No organism was put on the Moon, none was shown growing there, and the model does not supply food, an atmosphere or liquid water. It asks whether some terrestrial cells could arrive alive and avoid immediate destruction. This is one study, not settled evidence that microbes already inhabit the lunar surface.

The headline temperatures are real, but they do not describe every patch

The familiar swing from minus 173 to plus 127 degrees Celsius captures the violence of a lunar night and day. It is not a forecast for every square metre, especially near the poles. The Moon’s axis is tilted only slightly, so the Sun stays close to the horizon there. Low sunlight can warm one ridge while leaving a neighbouring depression in darkness.

Some crater floors never receive direct sunlight and are called permanently shadowed regions. NASA’s Lunar Reconnaissance Orbiter has measured portions of polar craters below minus 246 degrees Celsius. The result is a patchwork: intensely lit slopes, seasonal shadows and exceptionally cold traps can sit close together.

This distinction matters because the study did not take a single Moon-wide temperature and apply it to every cell. Its predictions depend on local terrain, illumination, season and the maximum temperature reached within a particular patch.

No microbes were placed on the Moon

The work, published in Science Advances on August 19, 2026, combined orbital observations with microbial survival limits measured in earlier laboratory experiments. Lead author Prabal Saxena of NASA’s Goddard Space Flight Center and colleagues studied Nobile Rim, Connecting Ridge and De Gerlache Rim, three south-polar regions relevant to future exploration.

The team modelled incoming ultraviolet light and maximum surface temperature. Regional maps reached roughly 60 metres per pixel for ultraviolet exposure and 240 metres per pixel for temperature. Selected candidate sites were examined at about five metres per pixel. Ray tracing then followed the changing angle of sunlight over periods from one day to at least seven days.

The open manuscript makes the boundary explicit: vacuum, energetic radiation and low temperature were considered less important than solar ultraviolet light and peak heat over the short timescales examined. That is a modelling choice based on previous tolerance measurements, not a claim that radiation or vacuum never matters.

Five ordinary hitchhikers were tested

The model included two fungi and three bacteria with very terrestrial addresses. Aspergillus niger is a dark-spored mould found in soil and damp indoor spaces, including bathrooms and air-conditioning systems. It has also been sampled aboard the International Space Station. Several Fusarium species, fungi commonly associated with soil and plants, formed the second group.

The bacteria were Bacillus subtilis, associated with soil, vegetation and the human gut; Staphylococcus aureus, commonly carried on skin and in nasal passages; and Deinococcus radiodurans, known for tolerating desiccation and doses of ionising radiation that kill most organisms.

These choices do not mean every bathroom mould or skin bacterium would behave identically. Strains differ, and a laboratory survival threshold is an imperfect stand-in for a cell attached to dust, fabric or spacecraft hardware. They are useful test cases because they span familiar human-associated organisms and unusually resistant ones.

The NASA explanation of the study notes the practical reason for examining them. People continuously shed biological material, and crewed vehicles cannot be treated with every microbial-reduction method used on a small robotic probe. A human skin patch the size of a pencil eraser can carry about a million bacteria.

Cold and vacuum can preserve instead of sterilise

On an exposed lunar surface, unfiltered solar ultraviolet light can break DNA and damage proteins quickly. Shade sharply reduces that dose. Permanently shadowed regions still receive weaker scattered light, but they avoid direct sunlight, while temporary shadows can protect material for hours or days.

Extreme cold sounds lethal, yet it often slows chemical reactions rather than instantly destroying a dormant organism. Vacuum pulls water from cells. In combination with cold, the effect resembles freeze-drying, or lyophilisation, a process routinely used on Earth to preserve biological material. A desiccated spore may be inactive without being irreversibly dead.

There is an important limit. Survival in this paper means retaining the potential to become active again under suitable conditions. It does not mean metabolism on the Moon. The surface lacks stable liquid water and a substantial atmosphere, and the researchers found no demonstrated route to feeding or reproduction.

What “weeks or even months” actually means

The study used one Earth day as its basic survival benchmark, partly because that is longer than the greatest interval between Apollo surface excursions. It also mapped uninterrupted protection for at least seven days. All five microbial groups could cross that longer threshold in parts of the permanently shadowed region at De Gerlache.

For Aspergillus niger, the most ultraviolet-tolerant organism considered, the model identified suitable conditions across 2 to 9 per cent of mapped, non-permanently-shadowed terrain in summer and 15 to 30 per cent in winter. Across all three regions, roughly 3 per cent remained suitable for that fungus for at least seven days.

The longer timescale in the headline comes from the lead researcher’s interpretation of the simulations. Saxena told Reuters that some organisms could survive for weeks to months in especially protected settings, including permanently shadowed craters and favourable autumn or winter conditions.

That is not a measured lifetime for every organism or every shadow. The paper directly demonstrates mapped thresholds of a day and, in selected locations, at least a week. It says the upper duration merits further study. Longer exposure could bring damage from ionising radiation, vacuum, abrasive dust and temperature cycling that the short-term screen does not fully capture.

A refuge could be crater-wide or boot-print-small

Lunar Reconnaissance Orbiter data made the exercise possible. Elevation measurements defined the terrain, while temperature and illumination observations constrained the environment. At the south pole, the low Sun gives small changes in topography an outsize effect.

A large crater can hold a permanent shadow, but the same geometry works at human scale. A rock, shallow hollow, rover track or astronaut’s boot print can create a temporary pocket of shade. The paper therefore considers viable niches ranging from parts of crater floors down to features made by exploration itself.

That does not turn every footprint into a biological refuge. A cell would still have to arrive there, tolerate launch and transit, avoid the hottest illuminated period and endure the remaining radiation. The result is probabilistic and spatial. It identifies where survival is physically plausible, not where contamination will certainly persist.

The main risk is confusing Earth material with lunar history

The Moon’s south-polar ice is scientifically valuable partly because it can preserve old volatiles and organic compounds. If future instruments detect familiar biological molecules, researchers will need to know whether they came from the Moon, a meteorite, rocket exhaust, a lander or a person.

That makes dormant cells significant even if they never divide. A viable fungus or bacterium could remain a recognisable Earth signal. Dead cells and fragments can also complicate chemical measurements. The preservation problem is therefore about scientific attribution, not fear that bathroom mould will spread across the Moon.

An earlier SpaceDaily report focused on Aspergillus niger’s ultraviolet tolerance. The broader model adds an operational point: before crews and vehicles heavily disturb a site, missions can record biological and organic baselines. Later detections can then be compared with samples taken before that traffic arrived.

Planetary protection here means records, not a lunar quarantine

Current policy reflects the Moon’s inability to support biological proliferation. A 2026 NASA planetary-protection handout says there are no limits on the types or quantities of organics a mission may bring. Surface missions must document propulsion products, and missions to the poles or permanently shadowed regions must also provide an inventory of organic substances.

The new study does not show that this policy is wrong. It offers evidence that contamination records may need enough spatial and seasonal detail to remain useful. A bag discarded in sunlight, material driven into a wheel track and cells released inside a permanent shadow may not share the same fate.

Future work could expose organisms to combinations of lunar vacuum, ultraviolet light, ionising radiation, dust and extreme cold for longer periods. Sampling around landers and human activity could also test whether the predicted niches retain biological signatures.

The Moon remains hostile to active Earth life. The subtler lesson is that an environment incapable of supporting growth need not sterilise every arrival immediately. At the south pole, a patch of darkness may act less like a habitat than a deep freezer, preserving a terrestrial hitchhiker long enough to matter to the science that follows.