Hardy, Microscopic ‘Water Bear’ Will Live Until the Sun Dies

A scanning electron micrograph of a tardigrade, or “water bear.” (Photo courtesy Bob Goldstein & Vicky Madden/UNC Chapel Hill)

(CN) – A microscopic, water-dwelling creature will be the last survivor should Earth experience an apocalyptic event, according to a new study that found the tiny animals will survive until the sun dies.

Known as tardigrades or “water bears,” these creatures are considered the toughest species on Earth, capable of living without food or water for up to 30 years. They can endure temperatures as high as 300 degrees Fahrenheit, and even survive the frozen vacuum of space.

Tardigrades – which grow to about 0.02 inches – would also survive any realistic astrophysical catastrophe and will be around for at least another 10 billion years, a team of researchers reports Friday in the journal Scientific Reports.

The team simulated tardigrades’ fate under three devastating cosmic scenarios, including the impact of a large asteroid and exploding stars in the form of gamma-ray bursts or supernovae. These events could boil off Earth’s oceans, wiping out the micro-animal in the process.

“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 co-author David Sloan, a postdoctoral researcher at Oxford University.

There are only a dozen known asteroids and dwarf planets with enough mass to boil Earth’s oceans after a collision, and none are close enough to pose a legitimate threat.

A supernova – the byproduct of a massive star’s death – would have to be within 0.14 light-years of Earth to kill off tardigrades. The closest star to the sun is four light-years away, and the probability of a large exploding close enough to Earth to wipe out all forms of life is negligible, according to the team.

The researchers found that gamma-ray bursts – the most energetic form of light – are also too far away to be considered a viable threat. Such a burst would have to be no more than 40 light-years away in order to boil off Earth’s oceans.

According to the team, the findings highlight the resilience of life in general, and expand the scope of life on other planets.

“The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions,” Abraham Loeb, study co-author and chair of the astronomy department at Harvard University, said. “Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions.”

Tardigrades are extremophiles – organisms that can adapt to severe environmental conditions that would harm other forms of life on Earth – and are important subjects to study as scientists continue to explore Jupiter’s moon Europa and Saturn’s Enceladus for subsurface oceans.

“The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars,” Loeb said.

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