This Moss Could Help Terraform Mars

Mosses rank among Earth’s most effective terraformers: they transform bare rock into productive soil. A group of scientists now suggests that these non-vascular plants might one day perform a comparable role on Mars.

Whether humanity should transport terrestrial life to our red neighbour is a separate matter - our record of introducing species on Earth is far from reassuring.

Yet, if we decide that altering Martian soil is justified in order to establish a second home for people from Earth, ecologist Xiaoshuang Li and colleagues at the Chinese Academy of Sciences believe they have identified a suitable candidate.

Mosses as Earth’s original terraformers

Earth’s land surface was once exceptionally hostile to life. That did not prevent bryophytes - the group now encompassing mosses, liverworts and hornworts - from leaving the relative security and fertility of the oceans to explore new territory.

These pioneers of land life succeeded because they could capture and process nutrients leaching from, or running across, rocks, while withstanding conditions harsh enough to destroy many other organisms. As bryophytes spread through Earth’s stony landscapes, they formed soils that ultimately enabled less resilient forms of life to make their way onto land.

That same genetic resilience still benefits mosses worldwide. The researchers believe their innate abilities could be used to colonise Mars, preparing the ground for less hardy organisms such as crops.

Syntrichia caninervis and its extreme habitats

Unlike the lush woodland mosses that may first come to mind, which live relatively comfortably compared with their ancestors, Syntrichia caninervis persists with remarkably few resources. It flourishes in deserts across China and the US, as well as in the frigid Pamir and Tibetan mountains, the Middle East, Antarctica and circumpolar regions.

North-west China’s Gurbantunggut Desert is a major centre for S. caninervis. The moss grows there more densely than anywhere else on the planet, despite temperatures spanning -40 °C to 65 °C (-40 °F to 149 °F) and relative humidity falling as low as 1.4 percent.

Li and the team subjected the moss to a series of trials, although forcing S. caninervis beyond its already extraordinary tolerance range proved difficult.

In laboratory experiments, they assessed its response to, and recovery after, severe dehydration, extended freezing (-80 °C for 3 or 5 years, and -196 °C for 15 or 30 days), radiation (at doses of 500 to 16,000 Gy), and Mars-like settings in the Chinese Academy of Sciences’ Planetary Atmospheres Simulation Facility (PASF).

Testing moss survival under Mars-like conditions

For the Mars simulation, the plants experienced pressure of roughly 650 pascals (Pa), close to Mars’s 680–790 Pa. Temperatures reached -60 °C at night and 20 °C by day, matching conditions in Martian equatorial and mid-latitude areas. The researchers also recreated atmospheric gas composition and ultraviolet radiation levels more closely resembling those on Mars.

For S. caninervis, dehydration was effortless. It also coped readily with severe cold: every frozen plant regenerated after thawing, while specimens dehydrated before freezing recovered substantially faster than those that remained waterlogged.

When exposed to radiation doses of 50 Gy - levels lethal to humans - S. caninervis showed no apparent ill effects. Its growth even appeared to accelerate at 500 Gy.

Mosses dried out before being placed in Mars-like conditions behaved as though nothing had occurred after only 30 days of recovery. Their hydrated equivalents required somewhat more time to recover, but nevertheless survived.

"Although there is still a long way to go to create self-sufficient habitats on other planets, we demonstrated 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 outer space."

Even if putting moss on Mars proves to be an awful idea, S. caninervis offers encouragement for life on Earth. Its ability to convert completely dry ground into a ‘living skin’, even after enduring such extreme conditions, suggests that life on our planet may be more resilient than we sometimes recognise.

The research was published in The Innovation.