We could terraform Mars with desert moss — but does that mean we should?

Artist's illustration depicting the terraforming of Mars — turning into a more Earth-like world.
A visualization of what Mars might look like over time, if humans managed to terraform the planet. (Image credit: Daein Ballard, CC BY-SA)

A desert moss could be the key to terraforming Mars, according to a recent study published by Chinese scientists.

Due to its extraordinary resilience, Syntrichia caninervis (S. caninervis), a moss found in extreme desert environments from Tibet to Antarctica, has been touted a "pioneer plant" for establishing a livable environment on Mars. Basically, scientists believe this plant could enrich the planet's rocky surface to enable the growth of other plants.

A few studies have explored alternative possibilities of these terraforming seeds, such as algae and lichens. "However, plants such as mosses offer key benefits for terraforming, including stress tolerance, a high capacity for photoautotrophic growth, and the potential to produce substantial amounts of biomass under challenging conditions," the new study's team wrote in the paper.

Mosses are believed to have been the first true land plants on Earth. As such, they developed a tolerance to extreme stress that allowed them to survive in our planet's very harsh early environment. 

But how extreme are we talking?

Related: If alien terraforming emits greenhouse gases, our telescopes could detect it

The moss trials 

The scientists subjected whole S. caninervis plants to conditions typically found on Mars: high doses of gamma radiation, low oxygen, extreme cold and drought. They report that the plants could withstand combinations of these conditions, even losing over 98% of their water content and still bouncing back within seconds —"drying without dying” is the term that was used. Perhaps even more astounding is the plant's ability to recover and grow new branches after being stored in a freezer at −80 degrees Celsius (-112 degrees Fahrenheit) for five years or in liquid nitrogen (-195.8 degrees C; -320.44 degrees F) for one month.

"Unique morphological features of S. caninervis, such as twisted leaves, conserve water by minimizing surface area and reducing transpiration, and the awns provide efficient photoprotection from intense UV radiation, extreme temperatures and water loss," wrote the team. "Meanwhile, the cell wall, cell membrane, and chloroplast and its membrane structure remain intact even in a completely dehydrated state." 

Under stress, S. caninervis enters a state of "selective metabolic dormancy," strategically preserving key metabolites — products of cellular metabolic pathways — needed for its speedy resurrection. "For example, S. caninervis plants maintain high levels of sucrose and maltose following stress; these sugars serve as osmotic agents and protectants that help preserve and stabilize cellular architecture," wrote the scientists. "Subsequently, the sugars provide the energy needed for rapid recovery upon relief from stressful conditions."

The Syntrichia caninervis moss.  (Image credit: Sheri Hagwood, hosted by the USDA-NRCS PLANTS Database)

Stress also triggers genes that encode for photoprotective proteins and enzymes that help scavenge harmful reactive oxygen species generated under radiation. "The multi-layered tolerance [provides] protection under stressful conditions and enables rapid cellular repair and the recovery of physiological activity when conditions suitable for growth arise," stated the team.

These findings, the scientists continue, lay the groundwork for building sustainable human habitats beyond Earth. Whether this statement is an exaggeration will depend on future experimentation — and may not even be achievable within our lifetime — but one important element missing from the discussion is not the feasibility of the science but the ethics behind it.

Do humans belong on Mars? 

This concept of terraforming another planet is not a new one and has its roots in science fiction. And, while the concept has been romanticized and thrown around in the media of late, there are serious concerns around social consequences on an extraterrestrial scale as a result of completely transforming an entire planet for human occupation.

In her essay titled The Thorny Ethics of Planetary Engineering, for instance, astrophysicist and NASA researcher Erika Nesvold outlines the dilemma quite clearly: "The goal of terraforming is to intentionally create an entire ecosystem on a global scale, which would more than likely destroy any existing ecosystem," she wrote. "Terraforming technology might even become feasible before we definitively determine whether extraterrestrial life exists on the planet or moon that we hope to transform. 

"But suppose we do discover evidence of existing microbial life on a planet like Mars," she continued. "Should this disqualify Mars as a target for terraforming? Should we avoid settling on Mars at all?"

The study was published on July 1 in the journal The Innovation. 

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Victoria Corless
Contributing Writer

A chemist turned science writer, Victoria Corless completed her Ph.D. in organic synthesis at the University of Toronto and, ever the cliché, realized lab work was not something she wanted to do for the rest of her days. After dabbling in science writing and a brief stint as a medical writer, Victoria joined Wiley’s Advanced Science News where she works as an editor and writer. On the side, she freelances for various outlets, including Research2Reality and Chemistry World.

  • Unclear Engineer
    A couple of thoughts:

    1. For this moss to spread and more or less cover Mars, it would need to be compatible with the chemicals in the surface of Mars. Mars has a lot of perchlorates in its soil. Have experiments been performed here on Earth to see how that would affect the spread of the moss? See https://en.wikipedia.org/wiki/Martian_soil for other issues with Martian soil supporting vegetation.

    2. Even if this moss could cover Mars, eventually, what effects would it have on the Martian atmosphere? Would it become more dense? Would it get a breathable percentage of oxygen? What are the actual benefits of getting Mars covered with this moss?

    Regarding the "ethics" of changing the ecosystem on Mars, it seems to me that we first need to determine whether there is any ecosystem on Mars. And, I think that determination should have a high priority - mainly because it is a matter of knowledge that could be lost if not properly investigated.

    But, once understood to be abiotic, I see no reason not to introduce biological elements to the Martian surface.

    On the other hand, if we do discover some sort of life on Mars, then I think we need to be careful not to disrupt it before we understand it. That is not because I think we need to be "fair" to bacteria or even amoebas - it is because it is in our own best interest to learn as much as we can about life that evolved somewhere besides on Earth. So long as humans still eat cows, pigs, chickens and just about all other forms of life on Earth, it would seem strange to give Martian microscopic life forms more rights than we give animals on our home planet.

    However, if we discover an underground society of large animals, that would get into some more ethical issues. But, I don't think anybody is expecting that.
  • Classical Motion
    Is the surface of Mars under constant radiation? Will Mars allow any life in the soil? Can any plant live thru that quick change in temp? It's a whopper and doesn't take months of steps to change.

    There really wasn't much information about growing there. It reverted to the big questions of going and what to do there.

    It might be a question of what is permissible. Mars might not be green. Or at least not Earth green.
  • Ken Fabian
    I'm not aware of any conditions under which such a plant could get liquid water - no rain, no dew, no frost melt because water vapor content of atmosphere is too low. I think the moss will just get desiccated and die. And if I understand correctly moss reproduction requires the presence of liquid water for the gametes to meet.
  • Classical Motion
    If moss was one of the first plants, it does seem reasonable that the water requirement would be high. The moss I know of live in damp areas.

    But I might have seen dormant dried up moss in arid regions and not know it. I only know the wet kind.
  • tkt
    If an atmosphere is created, what keeps it on the planet?
  • Classical Motion
    Gravity with and ionized air cap on top. The top cap works with the Earth's M and E fields to bound the top ionized layer. Earth's EM fields also keep that air from being blown away with solar wind.

    What air does escape is replaced with natural re-cycle processes. We do leave a trail thru space. A debris trail. All planets do, maybe not Mercury. Some say a faint trail.

    This ionized blanket can wave much faster than water. And might turn out to become a very sensitive and valuable instrument. A large sensitive instrument.

    The high atmosphere has properties just like quantum sensors do. If we could find a quick and precise alignment method, we might use it to detect the smallest of space "distortions". And one heck of a radio receiving antenna.

    Many possibilities.
  • Unclear Engineer
  • Classical Motion
    Maybe the easiest way to get an atmosphere on Mars is to take it out to a gas planet and dip it.
  • ThinkitThroughPeople
    There are a number of ways to regulate terraforming. You can ban it entirely, encourage it, or set up rules and criteria. The author of the article appears to be for banning. First off, if there is the potential for a large profit or gain, the ban everything position will be crushed. So how do we limit damage, call it the "Pandora" problem. A planet with something of value, inhabited, but not hospitable (even a chlorine vs oxygen based animal life atmosphere).