Also known as "water bears", these eight-legged micro-animals live in the least habitable places on Earth, from Antarctica to the deep sea.
The study, described in the journal Scientific Reports, considered three possible cataclysmic events: an asteroid impact, a supernova and a gamma ray burst. "If tardigrades are Earth's most resilient species, who knows what else is out there".
The tardigrade is basically the poster child for extremophiles. No problem. Temperatures plummeting to -272° Celsius or skyrocketing to 150°?
Calculating the probability of each of those events, and factoring in the heightened temperatures and pressures in which tardigrades can survive, the researchers found an incredibly tiny probability that an ocean-boiling, life-ending event would occur within 10 billion years.
They can survive radiation up to 6,200 gray (Gy). To exterminate tardigrades, something would have to boil the oceans away (no more water means no more water bears).
"Surprisingly we find that although human life is somewhat fragile to nearby events, the resilience of Ecdysozoa such as Milnesium tardigradum renders global sterilisation an unlikely event", the study's conclusion reads.
"They actually ran the numbers on everyone's favorite natural doomsday weapons", marvels Seth Shostak, an astronomer at the SETI Institute in Mountain View, Calif. However, none would be serious enough to completely eradicate all life. A supernova - the explosion of a massive star after it burns through its fuel - would have to happen within 0.13 light-years of Earth, and the closest star big enough to go supernova is almost 147 light-years away.
Researchers from Oxford could find little or no way to eliminate them from Earth, predicting a lifetime of around 10bn years. But the fact that tardigrades are so resistant to other potential apocalypses in the interim implies that "life is tough, once it gets going", Shostak says.More news: American Doctor Approved to Travel to United Kingdom in Charlie Gard Case
"In this context there is a real case for looking for life on Mars and in other areas of the solar system in general", Batista said.
So when that next mass extinction happens, it might be up to tardigrades to ensure life goes on.
Only a dozen objects, including the dwarf planet Pluto, are big enough that they would cause Earth's oceans to boil if they hit, but none are on a trajectory to intersect with our orbit. Of course, other asteroids may crash into the world and kill humans - they just wouldn't wipe out the stalwart tardigrades.
"Without our technology protecting us, humans are a very sensitive species", he said. Even subtle changes to our environment can have a drastic effect on our health.
Gamma-ray bursts would need to be no more than 40 light years away to pose a threat to life on Earth.
"There is a third scenario, where life continues around geothermal vents on a rogue planet until capture by a new host system, or the source of heat is extinguished... life could [endure] on a rogue planet long enough for it to be recaptured [into another solar system]."
A new study examines the ways small organisms called tardigrades could endure even if Earth were faced with gamma-ray bursts, supernova blasts or deadly asteroids. "The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions".