The amazing hardiness of tardigrades

TINY eight-legged creatures known as "water bears" can survive the vacuum and radiation of space, research published today claims.

It was the first time that an animal has been tested for survival under open-space conditions, the European scientists that authored the report wrote in this month's edition of the US journal Current Biology.

The creatures, known as tardigrades, are tiny - between 0.1mm and 1.5mm long - and are commonly found on wet lichens and moss.

They are resistant to drying out, show strong resistance to heat, cold and radiation, and can be brought back to life after years of dryness.

The animals have been able to survive in extreme environments ranging in temperature from -272C to more than 151C, as well as pressure equivalent to 300 times the pressure of the atmosphere.

Researchers exposed dried-up tardigrades to open space conditions - vacuum, ultra-violet radiation from the sun and cosmic radiation - while aboard the FOTON-M3, a European Space Agency spacecraft launched last September that orbited 270km above the Earth.

Upon returning home, scientists determined that most of the tardigrades survived exposure to vacuum and cosmic rays.

Some even survived the exposure to solar ultra-violet radiation that is more than 1000 times higher than ultra-violet radiation on the Earth's surface.

The survivors were even able to reproduce well after their space trip, the researchers wrote.

The tardigrades' extreme resistance to UV radiation "is perhaps most surprising", they added.

"How these animals were capable of reviving their body after receiving a dose of UV radiation ... under space vacuum conditions remains a mystery," wrote the team of authors led by Ingemar Jnsson of Kristianstad University in Sweden.

"It is conceivable that the same cellular adaptations that let them survive drying out might also account for their overall hardiness."

Tardigrades, of which there are some 600 species, are found across the Earth from mountaintops to the depths of oceans.

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