Plants can be quite tough – they will survive forgetful caretakers, aggressive pets, and other potentially life-threatening events. Apparently, these dangers cannot be compared to the ability of some plants to survive: the extreme conditions of outer space.
According to a new study published today in iScience, Physcomitrium patents—an extremely common algal species—can survive for up to 9 months outside the International Space Station. Additionally, 80% of the algal spores returned to Earth and continued to grow healthy, breaking new ground in astronomy research at the beginning of humanity’s missions to the Moon, Mars, and beyond.
“Space imposes several extreme stresses simultaneously, and we expected that almost all the spores might die,” senior author Tomomichi Fujita, a biologist at Hokkaido University in Japan, told Gizmodo in an email. “Instead, many remained viable and apparently evolved into completely normal plants. It also contributes to the discussion about the resilience of life beyond Earth.”
life beyond earth
This is not the first time that researchers have tested how the extreme conditions of outer space affect Earth-born creatures. In fact, astrobiologists often recruit particularly robust creatures – usually microbes or other microorganisms such as tardigrades – that are known to withstand the harsh conditions on Earth. An experiment in 2005 sent lichens into space for about two weeks, while in 2022 researchers found that cyanobacteria and fungi can withstand extraterrestrial conditions for months.
Moss, on the other hand, was already known for its remarkable survivability, being “one of the earliest plants to colonize land,” and known to thrive in Antarctica, volcanic areas, mountain peaks and more, Fujita explained.
“We wondered: If mosses could lead to barren lands on the early Earth, could their spores also withstand the space environment and contribute to future efforts to green the Moon or Mars?” Fujita thought. Physcomitrium patents It was also well understood genetically among researchers, making it an ideal species for analyzing the effects of outer space on the plant’s genetic material.
The moss, a dried, mature sporophyte – moss structures that contain thousands of spores – flew into space aboard Cygnus NG-17 in early 2022 and returned to Earth aboard SpaceX’s CRS-16 in 2023. Excluding brief storage periods, Kai remained exposed to space on a specially designed panel for 283 days (fun fact: that’s three days less than the famously “stranded” Starliner crew earlier this year, although these human astronauts were inside the ISS, not outside).
moss life in space
While in space, Kai endured “vacuum, cosmic radiation, extreme temperature fluctuations, and microgravity,” Fujita explained. To put this in perspective, the temperature alone was anywhere between -320.8 and 131 degrees Fahrenheit (-196 and 55 degrees Celsius). And so, Fujita’s team expected that “the survival rate may be close to zero.”
“The biggest challenge was uncertainty,” he said. “We had no way of knowing how much damage the combined stresses of space would cause because such conditions cannot be replicated on the ground.”
To their pleasant surprise, they were completely wrong. Upon the moss’s return to Earth, Fujita’s team assessed the combined effects of such elements on the moss’s germination rate, growth pattern, photosynthetic activity, and cellular integrity.
They found that an astonishing 80% of the spores survived the space journey, while about 90% of the spores that survived were able to germinate or grow. Chlorophyll levels in the moss were also generally consistent, according to the paper.
That said, the study focused on a single type of moss, meaning it can’t capture the full extent of how mosses — or plants, for that matter — respond to similar conditions, the paper noted. Space experiments are generally difficult to conduct, but Fujita is determined to continue building on the latest findings.
“This is not just a ‘Kai in space’ story,” Fujita said. “It’s part of a larger scientific effort to understand how life adapts to extreme environments, how ecosystems can be created in closed systems […] It is also a powerful reminder that life is more resilient than we can imagine.”