The desert moss Syntrichia caninervis is a promising candidate for colonization of Mars due to its extreme ability to tolerate harsh conditions that are fatal to most life forms. The moss is known for its ability to tolerate drought, but researchers report June 30 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 these three stressors combined. In all cases, prior desiccation seemed to help the plants cope.
“Our research shows that the ecological resilience of S. caninervis is superior to that of some highly stress-tolerant 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 colonizing extraterrestrial environments, laying the foundation for building biologically sustainable human habitats beyond Earth.”
A small number of previous studies have tested the ability of microorganisms, algae, lichens and plant spores to withstand the extreme environments of space or Mars, but 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 ground cover often found in arid regions. Given the moss’s ability to survive extreme environmental conditions, the researchers decided to test its limits in the lab.
To test the moss’s cold tolerance, the researchers stored plants at -80°C (in an ultracold freezer) for 3 and 5 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 plant growth. By comparison, humans experience severe convulsions and death when exposed to about 50 Gy. “Our results indicate that S. caninervis is among the organisms that are most resistant to radiation,” the researchers write.
Finally, the researchers tested the moss's ability to endure Mars-like conditions using the Chinese Academy of Sciences' Planetary Atmospheres Simulation Facility. The simulator's Martian conditions included air that was 95% CO2temperatures ranging from −60°C to 20°C, high levels of UV radiation, and low atmospheric pressure. Dried moss plants achieved a 100% regeneration rate within 30 days after being exposed to Martian conditions for 1, 2, 3, and 7 days. Hydrated plants, exposed to the simulator for only one day, also survived, although they regenerated more slowly than their dehydrated counterparts.
'While there is still a long way to go to create self-sustaining habitats on other planets, we have realized the great potential of S. caninervis as a pioneer plant for growth on Mars,” the researchers write. “Looking to the future, we expect that this promising moss could be brought to Mars or the Moon to further test the possibility of plant colonization and growth in space.”
This research was supported by the Chinese Academy of Sciences, the Leading Talents in Technological Innovation Program and the Third Xinjiang Scientific Expedition Program.
