Abstract
On board of the NASA Long Duration Exposure Facility (LDEF), spores of Bacillus subtilis in monolayers (10 6/sample) or multilayers (10 8/sample) were exposed to the space environment for nearly six years and their survival was analyzed after retrieval. The response to space parameters, such as vacuum (10 −6 Pa), solar electromagnetic radiation up to the highly energetic vacuum-ultraviolet range (10 9 J/m 2) and/or cosmic radiation (4.8 Gy), was studied and compared to the results of a simultaneously running ground control experiment. If shielded against solar ultraviolet (UV)-radiation, up to 80 % of spores in multilayers survive in space. Solar UV-radiation, being the most deleterious parameter of space, reduces survival by 4 orders of magnitude or more. However, up to 10 4 viable spores were still recovered, even in completely unprotected samples. Substances, such as glucose or buffer salts serve as chemical protectants. With this 6 year study in space, experimental data are provided to the discussion on the likelihood of “Panspermia”.
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