International Space Station
An experiment showed that the moss lived for 283 days outside the International Space Station and a mathematical model estimates that it could survive up to 15 years in the inhospitable conditions of Space.
Mosses conquered some of the most inhospitable environments on Earth long before humans arrived. They cling to Himalayan peaks, spread across Antarctic ice and colonize recent volcanic lava. These ancient plants, among the first to migrate from water to land 500 million years ago, survived multiple extinctions en masse thanks to its resilience.
Researcher Tomomichi Fujita, from Hokkaido University, wondered whether this resilience extended beyond the Earth’s atmosphere, so he sent mosses to the ultimate extreme environment: the vacuum of Space.
Space is spectacularly hostile to life. The vacuum would make human blood boil. Cosmic radiation passes through unprotected cells. Temperatures fluctuate drastically between extremes. Unfiltered solar ultraviolet light breaks down organic molecules with ruthless efficiency. Most organisms, including humans, would die in seconds after exposure.
The experience of sending mosses to Space seems absurdly simple. In March 2022, hundreds of moss sporophytes, tiny capsules containing reproductive spores, were launched to the International Space Station aboard a Cygnus cargo spacecraft. The astronauts fixed the samples outside the stationwhere they remained completely exposed to space for 283 days before returning to Earth in January 2023. No protection, no shielding, just moss against the universe.
The moss not only survived. More than 80% of spores returned aliveand all but 11% of the survivors successfully germinated in the laboratory, growing into healthy new moss plants. Chlorophyll levels remained largely normal, with only a modest 20% reduction in a photosensitive compound, which did not affect the overall health of the spores.
Before sending the moss into orbit, Fujita’s team carried out extensive tests on the ground using low-lying terrestrial moss, a species well studied for its genetics and development. They subjected young mosses, stem cells specialized in responding to stress, and sporophytes to simulated spatial conditions. The young mosses died quickly. Stem cells fared better, but still had high mortality. The sporophytes turned out to be remarkably resistant, demonstrating a tolerance to ultraviolet radiation about 1000 times greater than that of other parts of the moss.
This protective advantage comes from the structure surrounding the spore, which acts as physical barrier and chemical shieldabsorbing harmful radiation before it reaches the vulnerable genetic material inside. This adaptation likely allowed bryophytes, the group of plants that includes mosses, to colonize the earth 500 million years ago and survive subsequent extinction events.
Using data from the mission, researchers built a mathematical model that predicts that these spores could survive for approximately 5600 days in Spacearound 15 years, although they emphasize that this is still a rough estimate that requires more data.
