In a discovery that has stunned biologists and space enthusiasts alike, a humble species of moss has survived nine months completely exposed to the vacuum of space outside the International Space Station (ISS). Not only did it endure the freezing void and intense cosmic radiation, but it also successfully regenerated and grew once returned to Earth.
The findings, led by researchers at Japan's Hokkaido University, represent a significant leap forward in our understanding of life's resilience and have profound implications for future space travel and the potential terraforming of other planets like Mars.
The Experiment: A "Suicide Mission" for Plants
The study, published in the journal iScience, focused on Physcomitrium patens (also known as Physcomitrella patens), a common species known as "spreading earthmoss." While scientists have long known that simple organisms like bacteria and tardigrades can survive in space, complex multicellular plants were thought to be far too fragile for such an environment.
To test this, Professor Tomomichi Fujita and his team devised an experiment that exposed the moss to the harshest conditions imaginable. They prepared samples of the moss in various stages of life and attached them to the outcome of the ISS, specifically on the Exposed Facility of the Kibo module.
For 283 days (about 9 months), the moss sat in the open void, subjected to:
The Vacuum of Space: A complete lack of pressure and water.
Extreme Temperatures: Wild fluctuations between freezing darkness and scorching sunlight as the ISS orbited Earth.
Cosmic Radiation: High doses of ultraviolet (UV) and cosmic rays that usually destroy DNA.
The Astonishing Results
When the samples were retrieved and brought back to Earth, the team expected the worst. "We expected almost zero survival," Professor Fujita admitted. "But the result was the opposite."
The team found that while the juvenile moss plants (protonemata) and leafy stems mostly perished, the sporophytes—specialized reproductive structures that encase spores—showed incredible resilience.
Survival Rate: More than 80% of the sporophytes survived the journey.
Regeneration: Once rehydrated in the lab, nearly all of the surviving spores germinated and grew into new, healthy moss colonies.
Damage Report: The only significant sign of stress was minor DNA damage and a reduction in chlorophyll levels, but the plants were otherwise functional.
"We were genuinely astonished by the extraordinary durability of these tiny plant cells," Fujita said.
How Did It Survive?
The secret lies in the moss's evolutionary history. Mosses were among the first plants to move from water to land millions of years ago. To survive that transition, they evolved mechanisms to withstand dehydration and intense sunlight—traits that accidentally prepared them for the vacuum of space.
The researchers believe the sporophyte structure acts like a heavy-duty spacesuit. It has a tough outer layer that likely shielded the delicate spores inside from the worst of the UV radiation and vacuum effects, allowing the genetic material to remain intact in a dormant state.
Implications for Mars and Beyond
This discovery is more than just a biological curiosity; it is a potential game-changer for space exploration:
Terraforming Mars: If moss can survive the vacuum of space, it is a prime candidate for being a "pioneer plant" on Mars. Its ability to turn rock into soil (a process it performs on Earth) could be the first step in creating a habitable environment on the Red Planet.
Life Support Systems: Moss is lightweight, hardy, and requires little maintenance. It could be used in future space colonies to produce oxygen, recycle waste, and even create soil for growing edible crops.
The "Panspermia" Theory: The survival of these spores lends weight to the theory of panspermia—the idea that life can hop between planets by hitching a ride on meteors or comets. If moss spores can survive months in space, it is theoretically possible for life to travel from one world to another.
A Note on Syntrichia caninervis
This finding complements another recent breakthrough involving a different moss, Syntrichia caninervis. In separate ground-based experiments, Chinese researchers found that S. caninervis could survive simulated Mars conditions (including extreme cold and high radiation) in a lab.
While S. caninervis was tested in a simulator, the Physcomitrium patens study is unique because it survived the actual environment of space for an extended period. Together, these studies suggest that mosses are likely to be the first "earthlings" to permanently colonize other worlds.
The Future
Professor Fujita's team is now looking into what specific genes allow the moss to repair its DNA after such heavy radiation exposure. Unlocking these genetic secrets could not only help us grow plants in space but might also lead to radiation-resistant crops for harsh climates here on Earth.
For now, the humble earthmoss has earned its place in history as one of the toughest travellers to ever leave our atmosphere.