FIG. 8.

Action spectrum of extraterrestrial solar UV inactivation of B. subtilis spores from three space experiments on board the missions Spacelab (SL) 1 (triangles), D2 (squares), and EURECA (circles). Using an optical filtering system, dry layers of spores were exposed to defined wavelengths and intensities of extraterrestrial solar UV radiation during periods when the samples were pointing towards the sun. The spores were either kept at atmospheric pressure in argon (solid symbols) or exposed to the vacuum of space during the whole mission (open symbols). (Data are modified from reference 74.)