A group of Japanese scientists conducted experiments on the model moss species protenema (larval mosses), brood cells (specialized stem cells activated under stress), and sporophytes (protected spores). They investigated Physcomitrium patent to identify the most resilient spores under simulated space conditions, which were then sent to the external environment of the International Space Station (ISS). After nine months in space, over 80% of the spores survived and maintained their capacity to germinate. These findings highlight the potential of land plants like Physcomitrium patent to endure extreme environments when studied in space.

With the recent rapid changes in the global environment, exploring new avenues for the survival of life beyond Earth has become essential.

Understanding how Earth-origin organisms adapt to extreme and unfamiliar conditions, such as those found in space, is crucial for expanding human habitats on the Moon and Mars.

Researching the survival limits of organisms in both terrestrial and extraterrestrial conditions enhances our comprehension of their adaptability and prepares us for the challenges of ecosystem maintenance.

“Most living organisms, including humans, cannot endure even a brief exposure to the vacuum of space,” explains Dr. Tomomichi Fujita, a researcher at Hokkaido University.

“Yet, the moss spores maintained their vitality even after nine months of direct exposure.”

“This offers astonishing evidence that life forms evolved on Earth possess unique cellular mechanisms to withstand the challenges of space.”

In this study, Dr. Fujita and colleagues examined Physcomitrium patent, a well-studied moss commonly referred to as spread earth moss, under simulated space conditions, which included high levels of ultraviolet radiation, extreme temperature fluctuations, and vacuum settings.

They assessed three structures: Physcomitrium patent — protenema, brood cell, and sporophyte — to determine which is best suited for survival in space.

“We anticipated that the combination of space-related stressors, like vacuum, cosmic radiation, extreme temperature changes, and microgravity, would result in greater damage than any isolated stressor,” remarked Dr. Fujita.

The research revealed that UV light posed the greatest threat to survival, with sporophytes exhibiting the highest resilience among the three moss structures.

Young moss could not tolerate elevated UV levels or extreme temperatures.

Although brood cell viability was significant, the encased spores demonstrated a resistance to UV light that was 1,000 times greater.

These spores survived and germinated after enduring temperatures as low as -196 degrees Celsius for over a week and withstanding heat up to 55 degrees Celsius for a month.

The scientists proposed that the protective structures surrounding the spores may absorb UV light while physically and chemically shielding the spores inside from damage.

This resilience is likely the result of evolutionary adaptations. Moss plants, which evolved from aquatic to terrestrial species approximately 500 million years ago, have survived multiple mass extinctions.

In March 2022, the researchers sent hundreds of sporophytes aboard the Cygnus NG-17 spacecraft to the ISS.

Upon arrival, astronauts affixed the sporophyte samples to the ISS’s exterior, exposing them to space for a total of 283 days.

The spores made their return trip to Earth aboard SpaceX CRS-16, which was returned to the laboratory for analysis in January 2023.

“We had anticipated the survival rate to be nearly zero, but the results were the opposite: the majority of spores survived,” said Dr. Fujita.

“We were truly astounded by the remarkable durability of these tiny plant cells.”

Over 80% of the spores successfully completed the intergalactic journey, with nearly all of them—except for 11%—able to germinate upon returning to the lab.

The research team measured chlorophyll levels in the spores, discovering that all types exhibited normal levels, apart from a 20% reduction in chlorophyll a. Though chlorophyll a is sensitive to changes in light, this decrease did not appear to hinder the spores’ health.

“This study exemplifies the incredible resilience of life that has developed on Earth,” said Dr. Fujita.

Curious about the duration spores could survive in space, the researchers utilized pre- and post-expedition data to formulate a mathematical model.

They projected that the encased spores could endure up to 5,600 days, or around 15 years, under space conditions.

However, they emphasize that this estimate requires further validation through larger datasets to more accurately assess how long moss can thrive in space.

“Ultimately, we hope that this research paves the way for developing ecosystems in extraterrestrial environments like the Moon and Mars,” Dr. Fujita concluded.

“We desire that our moss research can serve as a foundation.”

For further details, refer to the published paper in iscience.

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Meng Chang Hyun et al. The extreme environmental resistance and space survivability of moss, Physcomitrium patent. iscience, published online on November 20, 2025. doi: 10.1016/j.isci.2025.113827