Last year, NASA sent a supply spaceship to the International Space Station (ISS). Its goods included thousands of tardigrades（缓步动物）. These creatures，each small enough to fit on the tip of a pencil， can be found just about anywhere: in oceans, trees, and probably your backyard. Scientists say some tardigrades would continue to exist even if most other life-forms on Earth were wiped out.
Tardigrades are survivors, which makes them well suited for space travel. Some can take about a thousand times the amount of radiation(辐射) that would kill a human. Unlocking how they can do that is important if we hope to send people to Mars someday. "If we can learn the tricks that tardigrades use to protect themselves," biologist Thomas Boothby says, "We could develop technologies that could protect humans.
The tardigrades on the ISS came from Boothby's lab at the University of Wyoming. Antecedent experiments exposed tardigrades to big doses（剂量） of radiation, and scientists made many amazing discoveries in this field. This time, Boothby wants to find out how they respond to low doses of radiation over a long period. That's the kind of exposure people living in space would get.
One way tardigrades protect themselves is by entering what's called a tun（桶）state. This adaptation lets them survive in places that dry out many times a year. Tardigrades dry up too. They curl（弯曲） up into tuns, or little balls，producing substances（物质） that protect their cells from damage. Their metabolism（新陈代谢）shuts down. They "essentially stop to live," Boothby says. "And they can stay like that for years or even decades."When water returns, tardigrades spring to life.
With this knowledge, scientists could develop foods that boost protective chemicals in astronauts' bodies. This might keep away from the effects of radiation. There is still lots of research to be done. "Right now, we're in the learning phase（阶段）," Boothby says, adding that other scientists will build on his research. "That's just the way science works."
