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Tardigrades will probably be alive to see our Sun die

Credits: University of Stuttgart

In about 5 billion years, our sun will die cooking the Earth in a wave of heat and radiation.  Humans will have probably already disappeared ages beforehand but at least one life form might be still be present according to researchers.  The tardigrade, also nicknamed the “little water bear” by the German zoologist Johann August Ephraim Goeze after it was discovered in 1773, is one of the more resistant species on the planet. 

Tardigrades are the most hardy life form on the planet.  Some species are known to resist temperatures as low as -272°C and as high as 150°C. Other species can survive many years without food, water or oxygen. Some seem to manage to live in empty spaces whereas others can live in the crushing pressures of the ocean.  Although the majority of these animals are found in humid habitats such as the moss that covers river rocks there is no doubt that tardigrades are impressive creatures, especially when it comes to their incredible resistance.

Life on Earth has already scummed to five massive extinctions.  However tardigardes have survived them all without any issue.  As these this creatures are extremely well equipped to survive the most extreme conditions, researchers are interested in finding out what conditions could destroy them.  Researchers from the University of Oxford and the University of Harvard believe that Earth’s oceans would literally need to boil for these creatures to suffer.  But could there really be an event that could make this happen?

tardigrade
Tardigrade. Credits: Wikipedia.

Asteroides, supernova, gamma-ray bursts

Researchers have looked at several possible scenarios.  The first hypothesis is that an asteroid could hit Earth which they believe is rather unlikely.  If tardigardes were going to be wiped out it would take a rock as big as Pluto to come hurtling towards the Earth’s surface. To our knowledge an event like this hasn’t been programmed in the next million years.  Therefore we need to think of other possibilities.  What about a supernova?  Could an exploding star affect our planet so much that tardigardes can no longer survive?

Again this is very, very unlikely.  It is for good reason that our planet evolves in an area of the Milky Way that is rather quiet.  Researchers have carried out some calculations. If a supernova was to blow enough radiation to breakdown Earth’s ozone protection, the star in question would need to be located 0.14 light years from our planet. However Proxima Centauri, the closest star to our sun is found 4.3 light year away. This star is also not ready to explode anytime soon.  However, even when it does explode, it wouldn’t affect our Earth enough to destroy tardigrades.

Well, what about gamma-ray bursts then?  This for of radiation is generally produced when two neutron stars collide or even when a massive star carried away by it’s momentum, finds itself caught by a black hole. Bursts that emerge are the most energetic in the universe.  However we benefit once again from our position. According to researchers, such radiation would only affect the Earth if we were positioned about 40 light-years away from the source. However, this is not the case so we have nothing to fear.

The death of the Sun

Lastly the only event that could destroy tardigrades is the death of the Sun.  In about 4 to 5 billion years our Sun will start to become a red giant, before dying and then collapsing in on itself.  The core of the sun will slowly start to shrink but it’s external layers will gradually extend to the Martian orbit, engulfing our planet in passing.Humans will have been dead for a long time already, but there is no doubt that the tardigrades will know how to hold on as long as possible… or at least to a certain extent.

This study obviously has exobiology implications.  It makes you think that other resistant species on Earth of the same type could possibly survive although in a hostile environment.

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,” stated David Sloan the leading author of the study. He continued “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.”

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