Tardigrades: Earth's unlikely beacon of life that can survive a cosmic catacylsm

Joan Terry
July 14, 2017

But before that point, the star would get hot and close enough to sterilize Earth for good, boiling away the world's oceans before consuming the planet or knocking it out of orbit - ending the tardigrades' reign at last. This finding, published July 14 in Scientific Reports, suggests that complex life can be extremely hard to destroy, which bodes well for anyone hoping Earthlings have cosmic company. Will there be any form of life left?

Three possible cataclysmic events - an asteroid impact, a supernova and a gamma ray burst - were considered by the study.

Scientists believe they have figured out their secret: they turn into a glass-like substance to cocoon the sensitive parts of the body from dehydration and other threats. "For the tardigrades to inherit the Earth, whatever catastrophe swept over the planet would have to return to normal-ish conditions within a matter of decades at most, or it really could be curtains", he said.

Water bears are so sturdy that they probably won't succumb to nuclear war, global warming or any astronomical events that wreak havoc on Earth's atmosphere - all of which could doom humans, says Harvard University astrophysicist Avi Loeb.

But, he added, if the tardigrades were the only survivors, they would face a struggle.

His Oxford colleague, Dr Rafael Alves Batista, contrasted the tardigrade's hardiness with human's relative fragility. Less than 20 known asteroids and dwarf planets, including Vesta and Pluto, would provide enough of a kick to boil off Earth's oceans with their impacts - and none are headed toward Earth anytime soon.

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Other species - like humans - aren't as durable.

Normal natural disasters that are fatal for humans - volcanoes, tsunamis, and the like - weren't even considered in the study: This is the mind-blowing endurance of the tardigrade, here; the suggestion that those events could be hazardous is nearly insulting. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. 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.

The researchers concluded the chance of a supernova, an exploding star, being big enough to kill all life here within our sun's lifetime was negligible. In the next seven billion years, the sun will swell into a red giant star, potentially engulfing Earth and surely sizzling away its water. If life that developed on planets like Mars is anything like tardigrades, it would stick around despite the planet's current inhospitable conditions, the researchers said.

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

Similarly, the subsurface oceans on Saturn's moon Enceladus and Jupiter's moon Europa may feature volcanic vents that provide heat, similar to the locations where tardigrades can thrive deep under Earth's sea, he said.

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