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Survival of Microbes in Space: Experimental Tests of Panspermia Rocco L. Mancinelli, Carl Sagan Center, SETI Institute, Mountain View, CA USA

   Panspermia as originally stated in the late 18^th and early 19^th centuries stated that  organisms travel throughout the universe and develop wherever  and whenever the environment is favorable.  Among the many criticisms of this definition of panspermia is that life cannot survive the hostile space environment. The question is: Can life survive that first step away from the home planet into the cold, desiccating radiation filled vacuum of space? And, can life survive on another planet? Space flight exposure experiments represent the first scientific tests of panspermia. Many organisms have flown and been exposed to space radiation and space vacuum. Most died instantly.  To date only spores of Bacillus subtilis, vegetative cells of Halorubrum chaoviatoris, Synechecossus Nageli, and the bottom portion of a colony of Rhizocarpon geographicum a bipolar epilithic lichen have managed to survive the rigors of space. In summary, terrestrial life can survive away from earth in the space environment, as well as in a simulated Mars environment. These results represent the first step in understanding the process of survival away from the home planet.