London, September 9 : A European Space Agency experiment has shown that microscopic animals called 'water bears' can survive in the vacuum of space.
According to a report in New Scientist, the tiny invertebrates, scientifically known as tardigrades, are the first animals known to be able to survive the harsh combination of low pressure and intense radiation found in space.
Tardigrades are known for their virtual indestructibility on Earth, and can survive intense pressures, huge doses of radiation, and years of being dried out.
To further test their hardiness, Ingemar Jonsson of Sweden's Kristianstad University and colleagues launched two species of dried-up tardigrades from Kazakhstan in September 2007 aboard ESA's FOTON-M3 mission, which carried a variety of experimental payloads.
After 10 days of exposure to space, the satellite returned to Earth.
The tardigrades were retrieved and rehydrated to test how they reacted to the airless conditions in space, as well as ultraviolet radiation from the Sun and charged particles from space called cosmic rays.
The vacuum itself seemed to have little effect on the creatures. But ultraviolet radiation, which can damage cellular material and DNA, did take its toll.
In one of the two species tested, 68 per cent of specimens that were shielded from higher-energy radiation from the Sun were revived within 30 minutes of being rehydrated.
Many of these tardigrades went on to lay eggs that successfully hatched.
But only a handful of animals survived full exposure to the Sun's UV light, which is more than 1000 times stronger in space than on the Earth's surface.
Before this experiment, only lichen and bacteria were known to be able to survive exposure to the combination of vacuum and space radiation.
"No animal has survived open space before," said developmental biologist Bob Goldstein of the University of North Carolina at Chapel Hill.
"The finding that animals survived rehydration after 10 days in open space - and then produced viable embryos as well - is really remarkable," he added.
According to astrobiologist Gerda Horneck of the German Aerospace Center, "This ability to survive in extreme conditions might be important when we consider the habitability of other bodies in our solar system or beyond."