Water bears are also known as tardigrades and grow to about half a millimetre.
Johannesburg - Cockroaches and Rolling Stones guitarist Keith Richards were once considered the two life forms most likely to survive global annihilation, but they are softies when one considers the real survivor - the water bear.

It takes a lot to kill a water bear. They have been launched into space, frozen, starved for years and still they come back.

They are so indestructible that a group of scientists believe they will not only outlast the human race, but will only be wiped out when the sun dies 10 billion years from now.

The new study published in Scientific Reports reveals that the water-borne, eight-legged, micro-animals will survive destruction by all and any astrophysical catastrophes.

Water bears are also known as tardigrades and grow to about half a millimetre.

They are found around the world living in marine and fresh water ecosystems and semi-aquatic environments. Tardigrades can be found on moss and lichens and they crawl around with a bear-like amble on their tiny legs, hence their name.

Water bears were first recorded in South Africa in 1907.

During the course of their research, the scientists from the universities of Oxford and Harvard considered three astrophysical catastrophes likely to cause mass extinction on the planet.

These included an asteroid strike, an exploding star and gamma ray bursts.

But for these catastrophes to affect tardigrades, the scientists believe the world’s oceans would have first to be boiled off and this would be unlikely to happen.

“There are many more resilient species on earth. Life on this planet can continue long after humans are gone,” said Dr Rafael Alves Batista, co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University.

The research suggests that life on Earth is likely to continue as long as the sun continues to shine.

Studies carried out on tardigrades have revealed they can survive without food or water for 30 years. They have also survived temperatures as extreme as 150°C. They have been frozen in space and continued living.

“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?” asks Bastista.

The research suggests that Mars could hold an alien form of water bear. It is difficult to eliminate all forms of life from a habitable planet.

“The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions.

“Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions,” says Professor Abraham Loeb, co-author and chair of the astronomy department at Harvard University.

Saturday Star