When the end of the world comes – whether by asteroid strike, gamma-ray burst, or supernova explosion – tiny creatures known as tardigrades will be the last survivors.
Tardigrades – also known as water bears, space bears, and moss piglets – are one of the most resilient creatures known to man.
They can survive extreme conditions that would be fatal – rapidly – to nearly all other known life forms. The tiny critters can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C) for several minutes, pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.
But just how resilient are tardigrades? Surely, something can kill them.
According to new research, there is only thing that could wipe out the species – the death of the sun.
Researchers at the University of Oxford wanted to explore the resilience of life itself, and the effects of potential astrophysical catastrophes on more than just humans.
“It’s an exciting time to be asking questions about life in the rest of the galaxy or universe,” says study co-author Dr. David Sloan, Post-Doctoral Research Associate in the Department of Physics at Oxford University.
Sloan, with Oxford colleague Rafael Alves Batista and Harvard University astrophysicist Abraham Loeb, wanted to see exactly what it would take to obliterate tardigrades. Using mathematical modeling, they explored the effects of three cataclysmic astronomical events: large asteroid impact, exploding stars in the form of supernovae, and gamma ray bursts.
The study, titled The Resilience of Life to Astrophysical Events, was published in the journal Scientific Reports on July 14.
In a statement about their findings, the researchers wrote,
The research implies that life on Earth in general, will go on as long as the Sun keeps shining. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, opening the possibility of life on other planets.
The new study published in Scientific Reports, has shown that the tiny creatures, will survive the risk of extinction from all astrophysical catastrophes, and be around for at least 10 billion years – far longer than the human race.
Tardigrades will likely survive all astrophysical calamities since those events will never be strong enough to boil off the world’s oceans.
Only the death of the sun will ultimately lead to the total extinction of life on Earth, including tardigrades, the researchers say.
In highlighting the resilience of life in general, the research broadens the scope of life beyond Earth, within and outside of this solar system.
Dr. Batista, co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, elaborates:
“Without our technology protecting us, humans are a very sensitive species. Subtle changes in our environment impact us dramatically. There are many more resilient species on earth. Life on this planet can continue long after humans are gone.
“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. If Tardigrades are earth’s most resilient species, who knows what else is out there?”
Dr. Sloan adds,
“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. 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. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on.”
“Tardigrade microfossils are reported from the Early Cambrian to the Early Cretaceous, 520 million to 100 million years ago. They have seen the dinosaurs come and go.”
It looks like they will exist for many more: The sun isn’t expected to die for at least 7 or 8 billion years – and will perhaps be around longer than 10 billion years, as the new study says.
This charming animated video explains more about the fascinating tardigrade.
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