Key points: Spores of the moss Physcomitrium patens survived 283 days outside the ISS and returned to Earth in January 2023. About 80% of spores remained viable and could germinate; roughly 11% failed to germinate. Researchers attribute survival to protective spore coats, and modelling suggests encased spores might endure up to ~5,600 days (≈15 years) in space. The study, published in iScience, raises prospects for future space agriculture and ecosystem experiments.
“Astonishing” Moss Survives Nine Months Exposed to Space — 80% of Spores Returned Viable
Key points: Spores of the moss Physcomitrium patens survived 283 days outside the ISS and returned to Earth in January 2023. About 80% of spores remained viable and could germinate; roughly 11% failed to germinate. Researchers attribute survival to protective spore coats, and modelling suggests encased spores might endure up to ~5,600 days (≈15 years) in space. The study, published in iScience, raises prospects for future space agriculture and ecosystem experiments.
09:47 AM, 11/21/2025Science
Moss spores that spent nine months directly exposed to space on the exterior of the International Space Station (ISS) returned to Earth still alive, a result that surprised the research team and fuels fresh interest in the possibility of growing plants beyond Earth.
In March 2022, Japanese researchers sent hundreds of spores of the well-studied moss Physcomitrium patens to the ISS aboard a resupply mission. Astronauts attached the samples to the station’s exterior, where they were exposed to vacuum, extreme temperature swings and intense ultraviolet radiation for a total of 283 days. The samples were returned to Earth on a SpaceX flight in January 2023 and analyzed in the laboratory.
“We expected almost zero survival, but the result was the opposite: most of the spores survived,”
— Dr Tomomichi Fujita, Hokkaido University
Remarkably, about 80% of the spores survived the mission and were capable of germination after their return. The team reported that roughly 11% of spores failed to germinate; the remaining fraction showed varying degrees of damage or uncertain viability in follow-up tests.
How the spores endured
Researchers believe the protective coat surrounding each spore acted as a shield: absorbing harmful ultraviolet radiation and chemically and physically protecting the inner cell. This natural shielding is consistent with how mosses and other extremophiles survive harsh environments on Earth, from Antarctic ice to volcanic rocks.
Implications for space biology and agriculture
Previous experiments had shown that certain algae and lichens can survive short exposures to space, but this is one of the first demonstrations that a more complex plant can remain viable after prolonged direct exposure. The finding suggests that some terrestrial life forms possess cellular-level mechanisms capable of withstanding space conditions for extended periods.
Using measurements taken before and after the mission, the team developed a model estimating that encased spores could potentially survive up to about 5,600 days (roughly 15 years) under the space conditions modelled. While this does not mean full-scale farming on the Moon or Mars is imminent, the result strengthens the idea that growing at least some plant species off Earth could be feasible as part of future life-support or ecosystem experiments.
Dr Fujita said the researchers hope the work will serve as an initial step toward constructing robust extraterrestrial ecosystems on bodies such as the Moon and Mars. The study was published in the journal iScience.