Moss Spores Survive 283 Days Outside ISS, Showing High Germination Rate

Samples of *Physcomitrium patens*, or spreading earthmoss, successfully endured 283 days attached to the exterior of the International Space Station (ISS) before being returned to Earth for analysis. The experiment, which began with the deployment of the spores on March 4, 2022, concluded with their recovery via a SpaceX capsule. Subsequent germination tests revealed a high rate of biological viability following prolonged exposure to the space environment.

The moss specimens were subjected to the vacuum, fluctuating extreme temperatures, microgravity, and unfiltered cosmic and ultraviolet (UV) radiation outside the orbital laboratory. Research led by Professor Tomomichi Fujita of Hokkaido University in Japan documented the findings, which were officially published on November 20, 2025, in the scientific journal *iScience*. The investigation established that over 80% of the spores directly exposed to the full spectrum of space conditions remained capable of growth, successfully germinating into normal plant structures upon return to terrestrial conditions.

Comparative analysis provided context for the resilience observed. A control group maintained under standard Earth conditions exhibited a 97% germination rate. Furthermore, a shielded set of spores, protected only from direct UV radiation, also registered a 97% germination rate, isolating the impact of the unfiltered UV component on the unprotected samples. This contrasts with prior research by Fujita’s group, which indicated that simpler moss filaments succumbed rapidly when confronted with UV radiation alone.

Professor Fujita hypothesizes that the multi-layered structure of the *P. patens* spore walls functions as an evolutionary, passive shielding mechanism against the cumulative stresses encountered in space. The unshielded spores achieved an 86% germination rate after the extended exposure. Mathematical modeling projections by the team suggest these specific spores could maintain functional viability in the vacuum of space for an estimated period of up to 15 years.

This study marks a significant benchmark, representing the first documented instance where a land plant species has demonstrated such prolonged survival capability while continuously exposed to the unfiltered rigors of the space environment outside Earth's protective atmosphere. The ISS, orbiting at approximately 400 kilometers, served as the testing platform for this research, which offers valuable data for astrobiology and planning for future long-duration crewed missions beyond low Earth orbit.

Professor Fujita continues his scientific inquiry at Hokkaido University's Faculty of Science, emphasizing that these findings substantially bolster the scientific understanding of life's inherent robustness and its potential persistence beyond Earth's confines.