Most of Earth's life forms will only survive if the sun keeps shining. They can even survive the deep sea, the frozen vacuum of space and radiation levels comparable to more than 70 times the amount of radiation given to treat cancer.
None of these events was thought to pose a lethal threat to the hardy tardigrade.
"'A lot of previous work has focused on "doomsday" scenarios on Earth - astrophysical events like supernovas that could wipe out the human race", David Sloan, a co-author on the new work and researcher at Oxford, said in the statement.
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.
"Because [tardigrades] are so hardy it means that events that we are anxious about as human beings, and rightly so, certainly wouldn't concern you if you just considered all life", he told The Guardian.
The upshot, he said, was that it was very unlikely any cosmic event would be so catastrophic as to sterilize an Earth-like planet where life, of the sort we know, had got going. "Species, or even entire genera may become extinct, but life as a whole will go on".
He observed: '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. "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.
Indestructible tardigrades will live until the dying Sun boils Earth's oceans
For a supernova to cause our oceans to boil the exploding star would need to be 0.14 light-years away, and the closest star to the sun is four light years away. They analyzed the probabilities of certain disasters, judged that Earth will not experience a calamity in which all its water is boiled off, and therefore concluded that tardigrades will be around until the sun explodes and engulfs our planet. In the next seven billion years, the sun will swell into a red giant star, potentially engulfing Earth and surely sizzling away its water.
"Life on this planet can continue long after humans are gone".
The researchers' paper, published in Scientific Reports, asks what it would take for the earth to be "sterilised", or all life on it to be killed. Much like supernovas, gamma-ray bursts are too far away from earth to be considered a viable threat.
In the paper, they write that there are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans, including Pluto.
The researchers say this discovery also broadens the scope for extraterrestrial life.
Say the authors, sub-surface oceans believed to exist on Jupiter's moon Europa and Saturn's Enceladus, "would have conditions similar to the deep oceans of Earth where tardigrades are found".
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.