Tiny invertebrates known as water bears are in one sense far tougher than humans who can crush hundreds of them underfoot: A new study has shown that the water bears can survive the vacuum and radiation of space. The water bears, who are more properly known as tardigrades, were launched into orbit aboard a European Space Agency satellite, where they were exposed for 10 days to the cold, low pressure, and intense radiation of space before being brought back down to Earth to study. Researchers already knew that water bears were unusually tough critters.
[T]hey prefer to spend their days in water, perhaps on a beach or a dewy patch of moss. But when the water dries up, the millimetre-long 'bears' can contract into a dried-out state and survive like that for years. They are also one of the few animals that survive year-round on continental Antarctica, and are among the most radiation-resistant animals known [Nature News].
The water bears were shot into space in their dried out state to increase their chance of survival. Upon their return to Earth, researchers rehydrated them and watched to see if they would spring back to life and reproduce normally. The cold, low pressure, and lack of oxygen had little impact on the water bears' survival and reproduction, researchers found, but the animals that were exposed to the highest level of radiation did have a higher mortality rate.
But a few of one species of tardigrade, Milnesium tardigradum, did manage to survive both the vacuum and extreme levels of solar radiation. This was surprising to the authors, given that solar radiation in outer space is more than 1,000 times higher than on the surface of the Earth [CBC].
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," says developmental biologist Bob Goldstein of the University of North Carolina at Chapel Hill, who was not affiliated with the study. "The finding that animals survived rehydration after 10 days in open space – and then produced viable embryos as well – is really remarkable" [New Scientist].