NASA's miscalculation? Microbes leaking from spacesuits could survive on the moon

The lunar south pole harbors craters that have never seen sunlight — places where organic matter from the earliest days of the solar system is believed to lie frozen and undisturbed. That is one of the main reasons humans want to go to the moon.

New calculations suggest those same craters could also be places where microbes carried from Earth might survive.

Until now, scientists assumed the harsh conditions on the lunar surface would kill any microbes on their own, which is why spacecraft bound for the moon have faced no sterilization requirements before launch.

A research team led by Prabal Saxena at NASA's Goddard Space Flight Center published findings challenging that assumption in volume 12, issue 34 of the international journal Science Advances.

A 2019 study concluded that microbes left near the lunar equator by Apollo-era astronauts were unlikely to have survived, given the unfiltered ultraviolet radiation in the absence of an atmosphere and the intense surface heat during the lunar day. Contamination control standards for lunar missions have since been based on that research.

The Saxena team noticed that the earlier study had not accounted for terrain, and set out to redo the calculations with topographic data included.

At the lunar south pole, the sun sits low on the horizon. Near the equator, the sun rises nearly overhead and casts little shadow, but at the poles the oblique angle creates long shadows. In some areas, hills and crater walls block sunlight from ever reaching the ground, leaving water ice intact.

The team overlaid surface temperature measurements from the Lunar Reconnaissance Orbiter with topographic maps built from laser altimeter data to calculate how much ultraviolet radiation accumulates at each point across the south pole. For the Artemis 3 candidate landing sites, they traced where sunlight strikes the terrain and where shadows fall, mapping conditions down to 5-meter-by-5-meter grid squares.

The team selected microbes repeatedly detected aboard the International Space Station or cultured in NASA clean rooms — organisms with a realistic chance of hitching a ride to the moon — and tested whether they could survive there. The five candidates were three bacterial species and two fungal species.

The upper temperature limit for growth among all five ranged from 41 to 58 degrees Celsius, and surface temperatures across nearly the entire lunar south pole in midsummer fell below that threshold. In terms of temperature alone, survival at the lunar south pole is possible.

The decisive factor turned out to be ultraviolet radiation. The team set the lethal dose as the amount of UV needed to reduce a population of one million microbes to a single survivor.

The most resilient organism was black mold (Aspergillus niger), commonly found on the space station. Its exceptional ability to repair damaged DNA means the UV dose required to kill it was far higher than for the bacterial species tested.

Calculations showed that black mold could survive for more than a day across up to 30 percent of the Artemis 3 candidate landing sites in winter conditions. Deinococcus — a bacterium known for its radiation resistance — fared one-fifth to one-ninth as well as the black mold, while Staphylococcus aureus and Bacillus subtilis survived across one-eleventh to one-thirtieth as much area.

Inside permanently shadowed craters that receive no sunlight, all five organisms survived for more than a week.

The research team drew a line at suggesting microbes could actually grow on the moon. Growth requires liquid water, and without an atmosphere the lunar surface cannot hold it — what the study confirmed is that microbes could persist in a dormant, metabolically inactive state.

However, the team argued that mere persistence is already a problem. The permanently shadowed craters are precisely the places expected to hold organic material from the early solar system.

Those craters are destinations scientists want to visit to understand where the building blocks of life came from. If Earth microbes establish themselves there first, any organic material discovered later could not be reliably identified as primordial — it might simply be contamination brought by humans.

Artemis 3, a crewed lunar mission scheduled for launch in 2027, is planned as the first human landing at the lunar south pole. The candidate landing sites are also under consideration as locations for a future lunar base.

Microbes could reach the lunar surface in several ways — when air is vented from an airlock, for instance, or when organic matter leaks from a spacesuit.

Footprints left by astronauts, rover wheel tracks and holes dug with shovels during lunar exploration could also become habitats for microbes.

In response, the team recommended that current contamination control standards be reviewed.

Meanwhile, the team acknowledged a limitation in their study: they did not factor in the ability of microbes to repair UV-damaged DNA, a calculation they said was too complex to include. Accounting for that capacity, they noted, would likely expand the estimated survival range further.

DOI: 10.1126/sciadv.aec0811

Paper information: Prabal Saxena et al., "Potential survivable niches for microbial life on the lunar south pole." Sci. Adv. 12, eaec0811 (2026).