Tardigrades have survived everything Earth has thrown at them over hundreds of millions of years. Now, they will help us understand whether Mars will ever be ready to welcome us.
About a dozen of them could fit into the period at the end of this sentence. Under the microscope, they appear little eight-legged bears moving in slow motion. They have been frozen, boiled, irradiated, thrown into the vacuum of outer space and recovered alive.
Scientists have been studying them for over two hundred years and they continue to have the capacity to surprise. They are called , although most people know them by the much nicer name of water bears.
And right now, they may be one of the best tools we have to understand how to survive on Mars, says .
A team of researchers at Pennsylvania State University just published a study that used tardigrades in a genuinely innovative way — not to test their endurance, but the hostility from Mars.
Specifically, the researchers wanted to understand how the regolith of the planet, the loose mineral deposits that cover the Martian surface, similar to the soil that covers ours, would interact with living animals.
Could be adapted to support the cultivation of plants destined for future human explorers? And could it even help protect the planet from contamination that humans could inadvertently bring with them?
To find out, researchers mixed active tardigradess with two different types of soil simulated martianboth designed to accurately replicate the mineral and chemical composition of regolith collected by NASA’s Curiosity Rover in a region called deposit Rocknestinside Gale Crater.
The first simulant, MGS-1was designed to represent the Martian surface comprehensively, and produced disastrous results. In just 2 days, the tardigrades showed a severely reduced activity. For an animal from space, it is extraordinary.
The second simulant turned out to be equally inhibitory, but much less harmful — which in itself gives researchers important information about which aspects of Martian soil pose the greatest risk.
Then came the surprise. When the team washed the simulant MGS-1 with water before introducing new tardigrades, the damage disappeared almost completely.
Something present not onlypossibly dissolved salts or another soluble compound, was responsible for the damage, and the water eliminated it.
The same property that made the regolith so hostile to life also transforms it into a potential natural barrier against terrestrial contamination. Mars, in a sense, could have its own built-in defense system.
This has a enormous importance for what scientists call planetary protection — the internationally agreed principle that we should not contaminate other worlds with life from Earth, and that we should not bring extraterrestrial contamination back home.
I know Martian soil is naturally hostile to terrestrial organismsthis is a cause for some relief. But at the same time, if a simple washing with water can neutralize this hostility, then future colonists might, after all, be able to treat the regolith to produce food.
Water is, of course, a precious resource on Marsmeaning that washing soil on an industrial scale is not a simple solution. But knowing that the problem has a solution is in itself a significant step forward. As the researchers themselves stated, they are beginning to unravel the components of a system of enormous complexity — piece by piece.
Water bears are what Earth has been able to throw at them over hundreds of millions of years — and they might be just the right animal to help us understand if Mars will be ready someday welcoming us.
