Moss Spores Survive 9 Months on ISS Exterior

Researchers at Hokkaido University in Japan have demonstrated that spores of the moss species Physcomitrium patens can endure nine months of exposure to the harsh conditions outside the International Space Station, with more than 80 percent remaining viable and capable of normal germination upon return to Earth.

The experiment began in March 2022, when astronauts attached samples containing thousands of moss spores, encased in protective sporophytes, to the exterior of the ISS via the Cygnus NG17 spacecraft. The spores faced a barrage of environmental stresses, including the vacuum of space, temperatures ranging from minus 196 degrees Celsius to 55 degrees Celsius, ultraviolet radiation, cosmic rays, and microgravity. After 283 days, the samples were retrieved and returned to Earth in January 2023 aboard a SpaceX CRS-16 capsule. Laboratory tests revealed that 86 percent of the spores exposed to full space conditions germinated successfully, nearly matching the 97 percent rate of control spores kept on Earth. Even those shielded only from ultraviolet radiation showed similar viability.

Tomomichi Fujita, a biologist at Hokkaido University and lead author of the study published...