Tardigrades Are So Tough, They'll Survive Until The Sun Dies

What if you could survive extreme pressures, temperatures, radiation, and asteroid impacts — but only if you shrank to be a millimeter long? That's the life of the tardigrade, a microscopic extremophile that can live through just about anything. And according to a paper published in Scientific Reports, when we say anything, we mean anything.

Tardigrade (water bear)
Waterbear Don't Give A Care
Here's just how tough tardigrades are: researchers have frozen them to -328 degrees Fahrenheit, heated them beyond 300 degrees Fahrenheit, subjected them to pressures 6,000 times that of our own atmosphere, and exposed them to doses of radiation thousands of times greater than it would take to kill a human. That's why when Oxford researchers wanted to figure out what it would take to wipe out all life on Earth, they turned to the tardigrade. Forget cockroaches surviving nuclear war; tardigrades will probably survive until the death of the solar system.

The researchers figured that if anything will decimate all life on our planet, it'll either be a massive asteroid impact, a nearby supernova, or a powerful gamma-ray burst. (Spoiler alert.) For their calculations, they assumed that whatever the event, it would have to be strong enough to at least boil off the Earth's oceans — whether tardigrades would survive beyond that as a species is anyone's guess, but it's a conservative starting place. Here's what they found.

Asteroids schmasteroids: For an asteroid to be large enough to boil off the oceans, it would have to weigh 2x1018 kilograms, or just a smidge less than Pluto. There are only about a dozen known asteroids and dwarf planets that match those numbers, but none of them are set to cross paths with Earth. Cross an asteroid impact off the list.
More like SuperNOva: A supernova — the giant explosion at the end of a massive star's life — with enough power to boil our oceans would need to happen 0.14 light years away. Our sun is too small to go supernova, and the next closest star is four light years away.
Gamma ray #burstworldproblems: Gamma-ray bursts are hundreds of times more powerful than supernovae, and generally happen during a supernova or in the creation of a black hole. But even they probably won't kill off the tardigrades: gamma-ray bursts are incredibly rare, and to boil the oceans, one would have to occur no more than 40 light years away. That gives it a pretty slim chance of happening.



Extraterrestrial Extremophiles
That's impressive, but is it important? If finding life on other planets is important, then yes. If there's an organism that can survive an asteroid, a supernova, and a gamma ray burst, then life as a concept is hardier than we thought. "Tardigrades are as close to indestructible as it gets on Earth, but it is possible that there are other resilient species examples elsewhere in the universe," says co-author Dr. Rafael Alves Batista. 

"In this context there is a real case for looking for life on Mars and in other areas of the solar system in general. If tardigrades are earth's most resilient species, who knows what else is out there."