Mysterious lifeforms may be lurking in the dark shadows of the moon, scientists say.

A new study, although not yet peer-reviewed, proposes the idea that microbes could potentially survive in the perpetual darkness of certain areas on the moon known as ‘permanently shadowed regions’ (PSRs).

These shadowy pockets of the lunar surface lie within craters and depressions near the moon’s poles. Because of the way this rocky satellite’s axis tilts, PSRs remain untouched by sunlight year-round. 

In space, microbes are usually killed by heat and ultraviolet radiation, according to study lead author John Moores, a planetary scientist and associate professor at York University in the UK. 

But because PSRs are so cold and dark, they may provide a safe harbor for bacteria, particularly the species that are typically present on a spacecraft like Bacillus subtilis that is known to improve gut health.

This terrestrial, spore-producing bacteria species usually dwells in soil or the guts of cows and sheep. But it has also been found living on the outside of the International Space Station (ISS). 

It’s possible that Earth-based microbes hitching a ride on spacecraft and astronauts that landed on the moon could have contaminated the lunar surface, potentially taking up residence inside PSRs and surviving for decades in a dormant state.

Figuring out whether these shadowed areas host dormant bacteria would have important implications for future moon missions, as these microbes could tamper with data collected from the lunar surface. 

‘The question then is to what extent does this contamination matter? This will depend on the scientific work being done within the PSRs,’ Moores told Universe Today. 

For example, scientists hope to take samples of ice from inside the PSRs to investigate where it came from. This could include looking at organic molecules inside the ice that are found in other places, like comets, he explained. 

‘That analysis will be easier if contamination from terrestrial sources is minimized,’ Moores said. 

If microbes are living in the moon’s PSRs, they exist in a dormant state, unable to metabolize, reproduce or grow, his findings suggest. 

But they may remain viable for decades until their spores are killed by the vacuum of space, Moores added. 

He has been investigating the presence of microbes on the moon for years, but until recently, he hadn’t thought to look inside the PSRs. 

‘At the time, we did not consider the PSRs because of the complexity of modelling the ultraviolet radiation environment here,’ he said. 

‘However, in the years since, a former student of mine, Dr. Jacob Kloos at the University of Maryland, had developed a sophisticated illumination model.’

Although sunlight never directly touches PSRs, they are exposed to faint sources of radiation such as starlight and scattered sunlight.

These radiation sources are significant because they contribute to the amount of heat and light inside these dark pockets, which are ingredients for life. 

With Kloos’ model, researchers can now survey the illumination conditions inside PSRs.

‘Furthermore, with the renewed interest in PSR exploration, we decided to take another look at these regions and realized we had all the pieces of the puzzle we needed to understand their ability to preserve terrestrial microbial contamination,’ Moores said. 

NASA’s Artemis III mission aims to put humans back on the moon by mid-2027, and has identified 13 PSRs near the lunar South Pole as potential landing sites. 

The agency selected these sites because PSRs are ‘rich in resources and in terrain unexplored by humans,’ according to NASA. For example, future astronauts could use ice that may be trapped within the craters for water, fuel and oxygen. 

To determine whether it would even be possible for microbes to survive in the moon’s PSRs, Moores and his colleagues ran several models to assess whether the trace amounts of heat and UV radiation that infiltrate these areas could sustain life.

The researchers looked at two PSR craters, Shackleton and Faustini, both of which are targeted landing sites for the Artemis mission.

Their findings suggest dormant microbes may be lurking within these shadowy craters. 

What’s more, any bacterial contamination that astronauts and spacecraft introduce to these PSRs ‘could remain detectable for up to tens of millions of years,’ the study states.

The researchers presented their findings at the 56th Lunar and Planetary Science Conference in March. 

‘The chance that there is already terrestrial microbial contamination in the PSRs is low but not zero,’ Moores told Universe Today. 

‘Several spacecraft have impacted within or near the PSRs. Though they all did so at high speed, past research by others has suggested that small numbers of spores can survive simulated impacts into regolith-like materials. 

‘If any microbes survived those impacts, they would have been widely dispersed.’