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Earth’s indestructible survivor: It’s not us

July 16, 2017, by Tim Radford

The tardigrade will see us out, and possibly, by a short head, the Sun as well.
Image: By Darron Birgenheier via Wikimedia Commons

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Climate change could be bad news for humans. But there is one indestructible survivor which will live through even a catastrophe.

LONDON, 16 July, 2017  Those who fear that runaway climate change could threaten all life on Earth can breathe again. One life form is destined to prove an indestructible survivor, so however bad things get, life itself will endure.

It will not, however, be human life. A trio of scientists with a morbid interest in the worst that could possibly happen have tested the resilience of life on Earth to calamity, and found a non-human survivor.

It is the tardigrade, or water bear. This tiny creature, less than a millimetre long, has been known to live through temperatures as high as 150°C or as low as minus 272°C, which is close to absolute zero. It can endure 30 years without food or water, survive the deep ocean and even a journey into space.

British and US scientists write in the journal Scientific Reports that they decided to explore events that could possibly sterilise life on Earth.

Although at least one study has found that runaway climate change could in theory heat the planet to such a level that the oceans would boil dry and make life impossible, this was not sudden enough or severe enough.

Ultra-resilience

They supposed three things very unlikely indeed: a direct hit from a dwarf planet or a very large asteroid, or a supernova less than a light month away (the nearest star is four light years away), or a mysterious gamma ray burst event within 40 light years. All these things could boil the Earth’s oceans dry, and at high speed.

Then they searched for an organism resilient enough to carry on after such a cataclysm. They found it. Milnesium tardigrada could be around for 10bn years: it might even have the staying power to survive, if only briefly, the death of the Sun.

“Without our technology protecting us, humans are a very sensitive species. Subtle changes in our environment impact us dramatically. There are many more resilient species on Earth. Life on this planet can continue long after humans are gone,” said Rafael Alves Batista, a physicist at the University of Oxford in the UK.

“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. 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?”

“Life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera, may become extinct, but life as a whole will go on”

The message is that life itself could be hard to expunge. Human life could perish, but life in general, and in tardigrade form, could go on. The lesson of the indestructible water bear is important for astrobiology, if not for immediate climate change.

“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,” said Dr Batista’s colleague David Sloan, also at Oxford.

“To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected.

“Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera, may become extinct, but life as a whole will go on.” – Climate News Network

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