杏吧原创

Tiny invertebrates called 鈥榳ater bears鈥� can survive in the vacuum of space, a European Space Agency experiment has shown. They are the first animals known to be able to survive the harsh combination of low pressure and intense radiation found in space.

Water bears, also known as tardigrades, are known for their virtual indestructibility on Earth. The creatures can survive intense pressures, huge doses of radiation, and years of being dried out.

To further test their hardiness, Ingemar J枚nsson of Sweden鈥檚 Kristianstad University and colleagues launched two species of dried-up tardigrades from Kazakhstan in September 2007 aboard ESA鈥檚 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.

Dried out

In one of the two species tested, 68% 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鈥檚 UV light, which is more than 1000 times stronger in space than on the Earth鈥檚 surface.

Before this experiment, only lichen and bacteria were known to be able to survive exposure to the combination of vacuum and space radiation.

鈥淣o animal has survived open space before,鈥� says developmental biologist Bob Goldstein of the University of North Carolina at Chapel Hill, who was not affiliated with the study. 鈥淭he finding that animals survived rehydration after 10 days in open space 鈥� and then produced viable embryos as well 鈥� is really remarkable.鈥�

This ability to survive in extreme conditions 鈥渕ight be important when we consider the habitability of other bodies in our solar system or beyond,鈥� says astrobiologist Gerda Horneck of the German Aerospace Center. But the results say little about how the animals might develop and reproduce in harsh environments, Horneck says.

The authors aren鈥檛 sure what causes the animals to be as resistant as they are to the effects of ultraviolet radiation. They speculate their hardiness might stem from the same adaptations that enable tardigrades to bounce back from being dried out.

Journal reference:

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