Tardigrades have survived exposure to outer space. There are about 1,300 known species in the phylum Tardigrada, a part of the superphylum Ecdysozoa consisting of animals that grow by ecdysis such as arthropods and nematodes.
According to Peter Guida, the head of NASA’s space radiation laboratory, one of the biggest radiation concerns for astronauts (and space-bound tardigrades) is a set of molecules called reactive oxygen species. Ionizing radiation enters the body and bores into wayward molecules that contain oxygen. In simple terms, those newly irradiated molecules then troll through the body causing all sorts of harm.
Tardigrades, in their desiccated state, produce an abnormal amount of antioxidants (yes, these actually exist outside the health-food world), which effectively neutralize those roaming, evil reactive oxygen species. Partly because of this talent, tardigrades have been found to withstand higher radiation doses with far greater success than researchers would otherwise believe they should.
The reason that tardigrades would have evolved to survive high radiation doses is a mystery, too. However, Miller points to a leading theory: Perhaps tardigrades evolved to be swept up by the wind and survive in the earth’s atmosphere—which would explain not only their hardiness, but also why they’re found all over the world.
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