Behold the humble tardigrade, or "water bear."
These tiny eight-legged invertebrates, measuring a millimeter in length at most, are found in damp environments around the world. They especially favor clumps of moss and lichen, the ground around the bottoms of trees and similar cool shady places.
When a water bear's habitat is dried out–a common occurrence if one happens to live in a bit of moss–it undergoes an amazing transformation. It collapses its legs into its body in a process called invagination. (Shut up.) Its body shrivels into a barrel shape, and it exudes a waxy substance that quickly dries to a watertight crust over its entire surface. In this "tun" form, it can live for months or years, its metabolic functions dropping to almost nothing, until it is placed once again in a moist environment. Then, over the course of a few hours, it uncurls its body, stretches out its tiny legs, shakes its tiny head (actually, I just made that part up) and goes about its tardigradely business. It can also accomplish this amazing feat of shutting itself down and reviving itself later when exposed to extreme cold, overly salty water or even seemingly lethal doses of radiation.
And as a group of scientists associated with the European Space Agency has discovered and reported in the latest Current Biology, these characteristics make water bears the only animals known–so far–to be able to survive unprotected in outer space. The vacuum that would cause an astronaut sans space suit to explode like a grape under a boot heel; the UV and cosmic radiation that would frizzle-fry an unwary spacefarer like a pat of butter in a colossal microwave: The meek little tardigrade, all wrapped up in itself, shrugs off these dangers and keeps on keeping on.
Dr. K. Ingemar Jonsson of Sweden's Kristianstad University led a team of researchers who, in September 2007, packed a crew of pre-dessicated water bears into the unmanned (but fully beared) FOTON-M3 spacecraft and sent them into a low Earth orbit for 12 days of zero-oxygen, zero-pressure, high-radiation excitement. When the hapless critters returned to Earth, Jonsson and colleagues rehydrated them and watched in glee as they slowly unfurled and went about their beary business, unfazed by their ordeal and probably quite hungry.
Can bio-engineered human/tardigrade chimeras, to whom the irradiated vacuum of space is as comfy as a bubbling Jacuzzi, be far behind? When the Sun goes supernova and swallows the Earth, will water bears survive and drift blithely away through the interplanetary inferno? Only time–and the imaginations of science fiction writers far more talented than I–will tell.
One more thing. No, two. No, three.