Moss Spores Survive 9 Months in Space, Offering Hope for Future Space Ecosystems

In a groundbreaking study, researchers have demonstrated that moss spores can survive the harsh conditions of outer space for nine months and still germinate upon return to Earth, suggesting potential applications in future space exploration.

The experiment, led by Dr. Tomomichi Fujita from Hokkaido University and published in iScience on November 20, 2025, involved exposing spores of the moss species Physcomitrium patens to the vacuum, extreme temperatures, and ultraviolet radiation outside the International Space Station (ISS). Remarkably, over 80% of the spores remained viable after the nine-month exposure, indicating their potential role in developing sustainable life-support systems in extraterrestrial habitats.

Mosses are known for their resilience, thriving in extreme environments on Earth, from the peaks of the Himalayas to the sands of Death Valley. This adaptability prompted researchers to investigate their survival capabilities beyond our planet.

The study focused on Physcomitrium patens, commonly known as spreading earthmoss, a model organism in plant biology. The researchers exposed three different structures of the moss to simulated space conditions on Earth:

• Protonemata: Juvenile moss structures.
• Brood cells: Specialized stem cells that emerge under stress conditions.
• Sporophytes: Encapsulated spores.

They found that sporophytes exhibited the highest resilience, particularly against ultraviolet (UV) radiation, extreme temperatures, and vacuum conditions.

Building on these findings, the team conducted an experiment to test the survival of moss spores in actual space conditions:

• Launch and Exposure: In March 2022, hundreds of P. patens sporophytes were sent to the International Space Station (ISS) aboard the Cygnus NG-17 spacecraft. The samples were attached to the exterior of the ISS, exposing them to the vacuum of space, microgravity, extreme temperature fluctuations, and cosmic radiation for 283 days.

• Return and Analysis: The samples were brought back to Earth in January 2023 via SpaceX CRS-16. Upon analysis, over 80% of the spores survived the nine-month exposure and retained their ability to germinate. This marked the first evidence that an early land plant can survive long-term exposure to the elements of space.

The study's findings have significant implications for future space missions:

• Ecosystem Development: The resilience of moss spores suggests that mosses could play a role in establishing basic ecosystems in extraterrestrial environments, such as the Moon and Mars. Their ability to survive and germinate after prolonged space exposure indicates potential for oxygen generation, humidity control, and soil formation in space habitats.

• Biological Research: Understanding the mechanisms behind the moss's resilience could inform the development of other life-supporting systems in space. Dr. Fujita noted, "This study demonstrates the astonishing resilience of life that originated on Earth."

While the results are promising, experts caution against overinterpreting the findings:

• Dr. Agata Zupanska of the SETI Institute emphasized that while spore resilience is important, it represents only an initial step toward the broader goals of growing plants in extraterrestrial environments. She stated, "The value of space plants is realized only if they can actively grow and thrive away from Earth."

This experiment builds upon previous studies that have explored the survival of various organisms in space. However, it is the first to demonstrate that an early land plant can endure long-term exposure to space conditions and remain viable upon return to Earth.

The successful survival and germination of Physcomitrium patens spores after prolonged exposure to space conditions represent a significant step forward in astrobiology and space exploration. These findings open new avenues for research into the use of resilient terrestrial organisms in supporting human life beyond Earth.