Earth’s most rugged plant just proved its resilience in space

Space keeps showing us how strange and unpredictable it can be. It is a place with no air, harsh radiation, and temperature swings that would shut down almost any living thing.

Yet we keep sending up new experiments because every so often, something survives that shouldn’t. Those moments remind us how much we still have to learn about life and its limits.

Why moss was sent to space

Moss grows on rooftops, sidewalks, rocks, and pretty much anywhere it can settle. It handles freezing winds and blazing heat. It hangs on in deserts and near volcanoes. That toughness made researchers wonder how far its limits actually go.

The experts sent a batch of moss spores on a trip that very few living things could survive. Those spores spent nine months on the outside of the International Space Station, facing everything space could throw at them.

When they came back, more than 80% were still alive and able to grow. This is the first time scientists have shown that an early land plant can handle long exposure to the raw conditions of space.

“Most living organisms, including humans, cannot survive even briefly in the vacuum of space,” said lead author Tomomichi Fujita of Hokkaido University.

“However, the moss spores retained their vitality after nine months of direct exposure. This provides striking evidence that the life that has evolved on Earth possesses, at the cellular level, intrinsic mechanisms to endure the conditions of space.”

How the idea took root

The project grew from basic questions about how plants evolve and handle stress. Fujita noticed how moss manages to colonize some of the toughest spots on Earth.

“I began to wonder: could this small yet remarkably robust plant also survive in space?”

Before sending anything into orbit, the team ran trials here on Earth. They worked with Physcomitrium patens, also known as spreading earthmoss.

The researchers tested three parts of the moss: juvenile moss called protonemata, brood cells that appear when the plant is stressed, and sporophytes that hold spores. They put these structures through conditions meant to mirror space.

“We anticipated that the combined stresses of space, including vacuum, cosmic radiation, extreme temperature fluctuations, and microgravity, would cause far greater damage than any single stress alone,” said Fujita.

What survived and what didn’t

UV radiation was the hardest challenge. Juvenile moss didn’t make it through high UV levels or extreme temperature swings. Brood cells did better.

The spores, tucked inside sporophytes, were in a league of their own. They showed about 1,000 times more tolerance to UV radiation than the other moss forms.

The spores also survived a week at −196°F and a month at 55°F without losing the ability to grow. The tough shell around the spores acted as a barrier. It soaked up UV radiation and protected the inner cell.

Mosses belong to a plant group that branched out onto land roughly 500 million years ago, long before roots or flowers existed. That protective structure likely helped early plants face sunlight, dryness, and other hazards on land.

From lab tests to outer space

To see if spores could handle actual space, the team loaded hundreds of sporophytes onto the Cygnus NG-17 spacecraft in March 2022.

Once they reached the International Space Station, astronauts mounted the spores on the station’s exterior, where they stayed for 283 days. The moss spores came home in January 2023 on SpaceX CRS-16. Back in the lab, the team checked how many survived.

“We expected almost zero survival, but the result was the opposite: most of the spores survived,” Fujita said. “We were genuinely astonished by the extraordinary durability of these tiny plant cells.”

More than 80% made it through the mission. Of those survivors, all but 11% germinated once they were placed in growing conditions.

Astonishing resilience of life

Chlorophyll levels were also measured, and everything looked normal except for a 20% drop in chlorophyll a. That compound reacts strongly to visible light. Even so, the spores grew just fine.

“This study demonstrates the astonishing resilience of life that originated on Earth,” Fujita said.

Curiosity pushed the researchers one step further. They combined their lab and space data to build a mathematical model.

The results suggested the spores could last up to 5,600 days in space, which is about 15 years.

The team noted that the estimate is rough. They would need more data to know how long moss could truly last beyond Earth.

Why this matters for the future

Moss is simple, and its spores pack serious staying power. That makes it an interesting candidate for early steps toward growing plants off-world.

Moss does not need much to survive. It can help build soil, support other organisms, and even handle long dormancy.

“Ultimately, we hope this work opens a new frontier toward constructing ecosystems in extraterrestrial environments such as the Moon and Mars,” Fujita said. “I hope that our moss research will serve as a starting point.”

If life on Earth can handle space better than expected, that could shape how future explorers grow food, recycle air, and build sustainable systems beyond our planet.

Moss might not look impressive at first glance, but this study shows just how much strength can come in a tiny package.

The full study was published in the journal iScience.

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