This moss survived 9 months outside the International Space Station in the harshness of space

Space is a harsh environment: it’s a vacuum with freezing temperatures, super high ultraviolet radiation and, of course, almost no oxygen.

But Japanese researchers have found a type of moss that doesn’t really care about much of that.

In a new study published on Thursday, researchers sent a type of moss called Physcomitrium patens to the International Space Station (ISS). This moss didn’t get to live in the comfy more-or-less Earth-like confines of the station, but rather was put outside into the harshness of space for nine months.

The researchers tested three different stages of the moss: protenemata, (juvenile moss); brood cells, (specialized stem cells); and sporophytes (reproductive structures that encase spores).

Not all of the stages survived.

When it came to the juvenile moss, it was unable to survive the high ultraviolet (UV) radiation or the extreme temperature fluctuations.

The brood cells had a better rate, surviving the freezing temperatures for 30 days, whereas 80 per cent of the sporophytes survived.

“This paper’s research proved that they can survive at least a nine-month exposure without growing at all,” said lead researcher Tomomichi Fujita, who is also a professor at Hokkaido University.

But what’s even better is that, when they were returned to Earth, roughly 90 per cent of the spores were able to germinate and grow in a laboratory setting.

The researchers will need to do further work to look at whether or not the spores changed while in space.

Plants in space

There has been a long history of testing the limits of multicellular organisms in space, particularly plants.

Plants are already grown on the space station.

But why bother?

Scientists say that, if humans are going to eventually live on the moon or even Mars, we need to figure out how to survive, which includes growing food for eating. But it could be about even more.

“I think [plants would] be pretty critical, not just for nutrition, but also just for mental health,” said Catherine Neish, an associate professor in the department of earth sciences at Western University in London, Ont.

“To see green things growing, to eat fresh produce, I mean, I think that would be a huge factor in an astronaut’s mental health.”

Neish was involved in an experiment in 2024 with then-undergraduate student Nima Abbaszadeh that looked at growing plants in lunar regolith (which is rocky material) and Martian regolith. Because regolith doesn’t have any organic elements, they had to add fertilizer to it. 

It worked — for the most part.

“I was surprised that anything grew at all,” she said. “The Mars soil didn’t work, but the lunar — we had two lunar soils, one representing the lava plains, the mare, and one representing the highlands — and yeah, it did a pretty good job growing in both.”

For Fujita, the idea of using moss, specifically Physcomitrium patens, came from the plant’s hardiness.

But how did the spores survive the extreme conditions of space?

The researchers believe that the structure surrounding the spore acts as a protective layer, absorbing the UV radiation. They also suggest that perhaps this layer blankets the inner spore to prevent any damage.

Such protection could also be how this hardy moss group, called bryophytes, may have transitioned from an aquatic plant to terrestrial about 500 million years ago.

Fujita says he hopes the findings help to create ecosystems on the moon and Mars.

“I hope that our moss research will serve as a starting point,” he said.