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Earth's last survivors are going to be water bears

15 July 2017

Scientists have known for some time that tardigrades are almost impossible to kill - although they dwell in water, they can be without it for 30 years - but research published Friday in Scientific Reports takes that notion a step further: The species will live through every disaster until the sun itself explodes.

Boffins have named a super-hardy, water-dwelling lifeform only half a millimetre in size as the Earth's toughest species.

It can live for up to 30 years without food or water, endure temperatures as high as 150C, and even survive in the frozen vacuum of space.

Instead, scientists considered star explosions (both supernovae and gamma ray bursts) and a major asteroid impact.

None of these events was thought to pose a lethal threat to the hardy tardigrade.

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"A lot of previous work has focused on "doomsday" scenarios on Earth - astrophysical events like supernovae that could wipe out the human race", Dr David Sloan, one of the researchers of Oxford University said.

"Because [tardigrades] are so hardy it means that events that we are anxious about as human beings, and rightly so, certainly wouldn't concern you if you just considered all life", he told The Guardian. "As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is".

"Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on", he said.

Now, a team of Oxford and Harvard researchers has found that tardigrades survive all astrophysical calamities, such as an asteroid, since they will never be strong enough to boil off the world's oceans.

"Tardigrades are as close to indestructible as it gets on Earth", study co-author Rafael Batista, from Oxford University, said in a statement.

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The tardigrade's extreme resilience points to another tantalising possibility - the existence of life elsewhere in our Solar System in places once thought too hostile. But researchers wanted to know what it would take to annihilate one of the world's most resilient creatures, so they turned to tardigrades. "The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions".

If a monster space rock crashes into our planet or radiation from an exploding star boils our oceans, humans and most other life forms will disappear. The physicists threw gamma rays, asteroids and supernovae at the tardigrades, and the little guys pretty much hung around, according to the mathematical models used in the experiment.

"This can guide us in which environments we should not search for life", astronomer Avi Loeb tells Dvorsky. But life that lived below ground or in large bodies of water would be shielded from harm and could survive, including the tardigrade. The tardigrade deemed to be an ultimate survivor on the Earth.

Supernovae or gamma-ray bursts, electromagnetic explosions that happen in other galaxies, could deplete the Earth's protective ozone layer which protects us from radiation.

"The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars". There are also no stars close enough to Earth capable of going supernova, which is when stars explode brightly in a final gasp before dying.

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"Without our technology protecting us, humans are a very sensitive species", Batista said. Life on this planet can continue long after humans are gone.

Earth's last survivors are going to be water bears