Tardigrades - which have a maximum size of 0.5mm - are water-dwellers and can live for up to 60 years. They are capable of going without food and water for 30 years, can live in temperatures ranging from -458°F (-272°C) to about 300°F (150°C), can survive massive doses of radiation, and can even exist and be revived after 10 days of being exposed to the vacuum of space. Researchers from the Universities of Oxford and Harvard, have found that these life forms will likely survive all astrophysical calamities, such as an asteroid, since they will never be strong enough to boil off the world's oceans.
Scientists scored the survival of the species over three rounds of tests which simulated a large asteroid impact, a blast from an exploding supernova star and a gamma ray burst, which is a huge explosion thought to be caused by a star collapsing.
"It is hard to eliminate all forms of life from a habitable planet", said Professor Abraham Loeb, Chair of the Astronomy Department at Harvard University and co-author of the paper discussing the results in the journal Scientific Reports. 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.
And gamma-ray bursts - thought to result from especially powerful supernovas or stellar collisions - are so rare that the researchers calculated that, over a billion years, there's only about a 1 in 3 billion chance of one killing off tardigrades.
"Although nearby supernovae or asteroid impacts would be catastrophic for people, tardigrades could be unaffected".
While research has looked at the various ways human life will go extinct, very little academic work has looked at what it would take to extinguish all life on earth, according to the study.
Another co-author, Dr Rafael Alves, argued that the findings open up questions about what other types of life may exist beyond our own planet.
"In this context there is a real case for looking for life on Mars and in other areas of the solar system in general", said Dr. Alves Batista said.
"There are many more resilient species' on earth". There are many more resilient species on Earth. To be able to boil the world's oceans the burst would need to be no more than 40 light-years away, and the likelihood of a burst occurring so close is again, minor. And gamma ray bursts of radiation, thought to be released by stars going supernova, are unlikely to occur at strengths high enough to strip away Earth's water in our corner of the galaxy.
Using mathematical modeling, Batista and his collaborators made a decision to try their best to predict what kinds of horrific disasters could actually wipe out even the gritty tardigrade.
Prof Abraham Loeb, co-author and chair of the Astronomy department at Harvard University, suggested Mars' history of once having a somewhat-habitable environment means we should be focusing there.
"This can guide us in which environments we should not search for life", astronomer Avi Loeb tells Dvorsky.
And the tardigrade deemed to be Earth's ultimate survivor.
"Without our technology protecting us, humans are a very sensitive species".
Scientists have investigated what will kill the world's most indestructible species and concluded that nearly nothing can - except the death of the sun.