A desert moss that has the potential to grow on Mars

The desert moss Syntrichia caninervis is a promising candidate for colonization on Mars thanks to its extreme ability to endure harsh conditions that are lethal to most life forms. The moss is known for its ability to tolerate drought, but researchers report in the journal The innovation that it can also survive freezing temperatures as low as -196°C, high levels of gamma radiation, and simulated Martian conditions with all three stressors combined. In all cases, prior desiccation seemed to help the plants cope.

“Our study shows that the environmental resilience of S. caninervis is better than that of some highly stress-resistant microorganisms and tardigrades,” write the researchers, including ecologists Daoyuan Zhang and Yuanming Zhang and botanist Tingyun Kuang of the Chinese Academy of Sciences.

“S. caninervis is a promising candidate pioneer plant for the colonization of extraterrestrial environments and lays the foundation for the construction of biologically sustainable human habitats beyond Earth.”

There have been some previous studies on the ability of microorganisms, algae, lichens and plant spores to withstand the extreme conditions in space or on Mars. However, this is the first study to test whole plants.

Syntrichia caninervis is a common moss species with a widespread worldwide distribution. It grows in remarkably extreme desert environments, including Tibet, Antarctica, and the circumpolar regions, as part of the biological soil crust, a widespread and resilient type of ground cover often found in dry regions. Given the moss’s ability to survive extreme environmental conditions, the researchers decided to test its limits in the laboratory.

To test the moss’s cold tolerance, the researchers stored plants at -80°C (in an ultracold freezer) for three and five years, and at -196°C (in a tank of liquid nitrogen) for 15 and 30 days. In all cases, the plants regenerated when thawed, although their recovery was slower compared to control samples that had been dehydrated but not frozen, and plants that had not been dehydrated before freezing recovered more slowly than plants that had been dried and then frozen.

The moss also showed that it is able to survive exposure to gamma radiation, which would kill most plants, and doses of 500 Gy even appeared to promote growth in the plants. In comparison, humans experience severe convulsions and death when exposed to about 50 Gy. “Our results indicate that S. caninervis is among the most radiation-tolerant organisms known,” the researchers write.

Finally, the researchers tested the moss’s ability to withstand Mars-like conditions using the Chinese Academy of Sciences’ Planetary Atmospheres Simulation Facility. The simulator’s Martian conditions include air that is 95 percent CO₂temperatures fluctuating between -60°C and 20°C, high levels of UV radiation and low atmospheric pressure.

Dried moss plants reached a 100% regeneration rate within 30 days after being exposed to Martian conditions for one, two, three, and seven days. Hydrated plants, exposed to the simulator for only one day, also survived, although they regenerated more slowly than their dehydrated counterparts.

“Although there is still a long way to go before self-sustaining habitats can be created on other planets, we have demonstrated the great potential of S. caninervis as a pioneer plant for growth on Mars,” the researchers write.

“Looking ahead, we expect that this promising moss could be taken to Mars or the Moon to further test the possibilities for colonizing and growing plants in space.”