Moss could survive in space for up to 15 years, according to international researchers, who sent moss spore samples to the International Space Station, where they survived in the vacuum of space for nine months before returning to Earth.
The samples had an 80% survival rate and were able to successfully germinate when they returned to the planet. The researchers analysed how well the moss survived with a computer model, which predicted that the spores could have survived for up to 5600 days – around 15 years.
The researchers found that UV radiation was the toughest element to survive, and the sporophytes were by far the most resilient of the three moss parts. None of the juvenile moss survived high UV levels or extreme temperatures. The brood cells had a higher rate of survival, but the encased spores exhibited ~1,000x more tolerance to UV radiation. The spores were also able to survive and germinate after being exposed to −196°C for over a week, as well as after living in 55°C heat for a month.
The team suggested that the structure surrounding the spore serves as a protective barrier, absorbing UV radiation and blanketing the inner spore both physically and chemically to prevent damage. The researchers note that this is likely an evolutionary adaptation that allowed bryophytes–the group of plants to which mosses belong–to transition from aquatic to terrestrial plants 500 million years ago and survive several mass extinction events since then.
In March 2022, the researchers sent hundreds of sporophytes to the ISS aboard the Cygnus NG-17 spacecraft. Once they arrived, the astronauts attached the sporophyte samples to the outside of the ISS, where they were exposed to space for a total of 283 days. The moss then hitched a ride back to Earth on SpaceX CRS-16 in January 2023 and was returned to the lab for testing.
The researchers hope that their work helps advance research on the potential of extraterrestrial soils for facilitating plant growth and inspires exploration into using mosses to develop agricultural systems in space.