In September 2007, while sun worshippers on Earth were warding off sunburn, tiny water-dwelling invertebrates called tardigrades – often referred to as “water bears” – were orbiting through space as solar UV radiation levels 1000 times those on Earth assaulted them. Their odyssey began with a question researchers had been asking for a while: Could these hardy organisms survive the radiation and vacuum conditions of open space and, if so, what could they teach us about maintaining human existence under extreme conditions? Results of the study, headed up by K. Ingemar Jönsson of Kristianstad University in Sweden, were published in the Sept. 9, 2008, issue of Current Biology.One of the most desiccation-tolerant animals – able to survive up to a decade in its dehydrated state – the tardigrade thrives in temperatures from near absolute zero to 303 °F. It is found in hot springs and in polar regions as well as on lichens and mosses. Representing 600 million years of evolution and comprising a phylum uniquely its own, it alternates between desiccated, inactive and hydrated, active states, and it rehydrates in minutes.Shown is the FOTON-M3 capsule that carried tardigrades into space in 2007 for the first time. Courtesy of the European Space Agency.The FOTON-M3 capsule transporting the tardigrades – dubbed “tardinauts” – was launched from Kazakhstan by the European Space Agency. It flew at a low orbit of 270 km, carrying the dehydrated specimens in a two-layer sample carrier in a Biopan-6 module, which was positioned outside the capsule. When the module was opened in space, two optical window types exposed the samples to two UV radiation spectra: MgF2 for the full spectrum (116 to 400 nm) and a cutoff filter for the 280- to 400-nm wavelengths – the UVA and UVB ranges. Specimens beneath a 1-mm aluminum layer tested endurance of vacuum and cosmic radiation.Some tardigrades endured a UV dose greater than 7000 kJ/m2 – enough to kill a human several times over. And, surprising the researchers, some reproduced postvoyage. The mechanics of tardigrades’ resistance is unknown. Jönsson speculates that their cuticle, a layered skin, prevents longer wavelengths from penetrating. Lessons related to cancer are impossible to learn now, but because the DNA of tardigrades survived or was repaired, genetic material could provide clues. In late 2007, the National Human Genome Research Institute prioritized the sequencing of the tardigrade genome. The results may blast scientists to new frontiers of knowledge about survival on Earth as well as in space.