Water bears survive space environment, study shows
Microscopic animals known as 'water bears' are able to survive the harsh environment of outer space, according to new research by European scientists. The space environment is extremely hostile to most life forms; temperatures are close to absolute zero (-273°C), and there is a vacuum and high radiation levels from the sun and stars. So far, some bacteria and lichens have proven their ability to survive in space. However, until now, no animal has been exposed to these conditions. Writing in the journal Current Biology, the German and Swedish researchers explain how they put minute animals called tardigrades to the test. Tardigrades, also known as 'water bears', are tiny invertebrate animals up to 1.5 mm long that are commonly found in damp environments, such as wet lichens and mosses. These environments are prone to drying out, and the tardigrades have evolved the ability to survive long periods of desiccation which may last for several years. Furthermore, these hardy creatures are able to withstand extremes of heat, cold and radiation. These characteristics mean that they have a better chance than most of surviving in space. Desiccated samples of two species of tardigrade were launched into space in September 2007 on board the FOTON-M3 mission of the European Space Agency (ESA). For 10 days, they whizzed around the planet in a low Earth orbit, between 258 km and 281 km above sea level. During that time, both adult tardigrades and eggs were exposed to the vacuum of space as well as to UV radiation and cosmic radiation. On their return to Earth, the samples were rehydrated and the scientists followed their progress to see if they would survive and reproduce. The samples that had been exposed to the vacuum alone thrived once rehydrated. However, mortality was high in the samples that had been blasted with solar radiation. Nevertheless, some specimens not only survived, but went on to reproduce successfully, despite their exposure to levels of UV radiation 1,000 times higher than those found on the surface of the Earth. 'How these animals were capable of reviving their body after receiving a dose of UV radiation of more than 7,000 kJm-2 under space vacuum conditions [...] remains a mystery,' the researchers write. The mechanisms which allow the 'water bears' to survive levels of radiation that would irreparably damage the DNA of human beings need to be studied further. The researchers speculate that these could include special mechanisms to prevent DNA damage in the first place, and an efficient DNA repair system.
Countries
Germany, Sweden