On March 4, 2022, astronauts placed 20,000 moss spores outside the International Space Station, where they endured extreme space conditions for 283 days. Following their retrieval, the spores were brought back to Earth in a SpaceX capsule for scientists to attempt germination. Remarkably, these attempts proved successful.

Mosses, one of the oldest land plants, are renowned for thriving in some of the planet’s harshest environments, such as Antarctica, volcanic terrains, and arid deserts. Tomomichi Fujita was part of the research team from Hokkaido University in Japan that conducted this groundbreaking experiment.

“We were curious whether these spores could withstand conditions in one of the most extreme environments imaginable: outer space,” he remarks.

Numerous studies have simulated the survival of various mosses and plants under extraterrestrial conditions, particularly those anticipated on Mars. However, this marks the first instance where researchers examined whether a specific type of moss can endure the actual conditions of space. The spores originated from the species Physcomitrium Patent.

A control group of spores that remained on Earth exhibited a 97 percent germination rate, comparable to another group of spores that were shielded from the damaging ultraviolet rays while still in space.

Astoundingly, over 80 percent of the spores that faced the totality of space—its vacuum, extreme temperatures, microgravity, ultraviolet light, and cosmic radiation—survived and grew into healthy plants. Researchers predict that some spores could remain viable in space for as long as 15 years based on these experimental results.

“Opening the sample felt akin to unlocking a biological time capsule: life that has endured the void of space and returned to full functionality,” Fujita expresses.

Prior to the experiment, the researchers had already assessed other living components of the moss, such as its filaments, under simulated conditions. They discovered that other life stages of this moss succumb to environmental factors like UV radiation, extreme temperature fluctuations, high salinity, and dehydration within days to weeks.

However, the spores appeared to withstand all these adversities. This is particularly impressive given that the spores outside the space station faced simultaneous attacks, while the Earth-based tests evaluated only one stressor at a time.

Fujita noted that the multilayered spore wall encasing the reproductive tissue acts as a “passive shield against harsh spatial conditions.”

He likens the spores to residing within their own spaceship, suggesting this might be an adaptive feature they developed to deal with the extreme environmental pressures present during the early stages of terrestrial life, hundreds of millions of years ago.

“Spores are, in essence, compact life capsules that lie dormant but are ready to reactivate when conditions are favorable,” he states. “It feels like evolution has given them their own survival pods designed to travel across time and space.”

Fujita cautioned that this research does not confirm the presence of extraterrestrial life, but it does bolster the concept that once life appears, it can be incredibly resilient. “The ability of terrestrial life to thrive under space-like conditions suggests that the fundamental building blocks of life might be more abundant and persistent than we typically assume.”

David Eldridge and fellow researchers from the University of New South Wales in Sydney emphasize that the ultimate test is not merely whether the spores can germinate on Earth, but if they can thrive in space.

“The critical point is to evaluate the growth rates of these taxa in space and determine if they can reproduce,” he concludes.