Microscopic tardigrades, also known as “water bears,” are the toughest animals on the planet, capable of withstanding intense radiation, extreme temperatures, and even the vacuum of space. The tardigrade, said researchers from Oxford and Harvard, will survive all foreseeable astrophysical catastrophes — asteroid strikes, exploding stars (supernovae) or gamma ray bursts — and “be around for at least 10 billion years.”

That is far better than the diagnosis for our own species. The point of this cheery study, published today in Scientific Reports, was to determine the conditions under which all life on Earth might be extinguished, and the phenomena that could instigate the premature sterilisation of the planet. It also suggests that once life emerges, it is surprisingly resilient and difficult to destroy, opening the possibility of life on other planets. This eight-legged wee beastie (they measure 0.5 mm in length and can only be seen through a microscope) can endure conditions that boggle the imagination, surviving for up to 30 years without food or water, and enduring temperature extremes of up to 300 degrees F (150 degrees C). Loeb and his colleagues, Rafael Batista and David Sloan, both from Oxford University, say tardigrades would be able to survive the destruction of the Earth’s atmosphere or a runaway greenhouse effect by seeking shelter in the ocean, which is why they were forced to consider astrophysical events powerful enough to deplete the planet of water. In a paper delightfully titled “The Resilience of Life to Astrophysical Events,” David Sloan and Rafael Alves Batista, both from the University of Oxford, and Avi Loeb, from Harvard University, estimated the odds that a space-borne catastrophe like an incoming asteroid would completely sterilize the Earth. The study thus suggests that there are many very resilient species' on Earth including tardigrades that could survive 'doomsday scenarios'. Life on this planet can continue long after humans are gone.”

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. To be clear, the three researchers aren’t concerned with the fate of humans—a fragile, fleshy species that, in Loeb’s words, can be “killed by climate change or affected by bad politics.” Instead, the trio wanted to know what it would take to wipe out all life on the planet. They have considered the impact that three potential catastrophic events could have on the planet's species – a massive asteroid impact and exploding stars in the form of supernovae or gamma ray bursts. Asteroids: There are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans (2×10^18 kg), these include (Vesta 2×10^20 kg) and Pluto (10^22 kg), however none of these objects will intersect the Earth’s orbit and pose a threat to tardigrades. Our closest star, Proxima Centauri, is already 4.25 light-years away and is too small to go supernova; even if it did, it would raise the ocean’s temperatures by a paltry 0.1 degrees Celsius. With all this in mind, the researchers hypothesise that there’s a one in a million chance that a catastrophic astrophysical event will kill all forms of life on Earth—tardigrades included—before the Sun grows old enough and hot enough to boil the oceans away. The scientists explain that impacts of gamma-ray bursts on humans and other animals on land could potentially be disastrous as the eradication of the ozone layer would leave these species exposed to lethal levels of radiation. The study, from Harvard and Oxford universities, detailed the threats to life on Earth over billions of years, finding that Earth-pummeling asteroids, nearby supernova blasts and gamma-ray bursts would be unlikely to completely sterilize Earth (taking out the little tardigrades in the process). Indeed, to find life outside Earth, it is necessary to establish under what conditions life can emerge and subsist on a planet – there are still a lot of uncertainties surrounding this.
A newly-published paper suggests that some tardigrades may outlive most life on Earth.