A century ago, S. Arrhenius formulated the theory of Panspermia, which postulates that microscopic forms of life, e.g.: spores, can be propagated in space and driven by the radiation pressure of the sun as a mechanism of transport for the germs of life from one planet to another . Recent discoveries, such as the Martian meteorites, the high UV resistance of mi-
croorganisms at the low temperature of deep space, and the recovery of viable spores after extended periods of time in space , have given support to revisit the theory of Panspermia. During a hypothetical interplanetary transfer process, the organisms have to cope with the following three major challenges: (1) The escape process, i.e.: removal to space of biological material that has survived being lifted from the surface to high altitudes; (2) the interim state in space, i.e.: survival of the biological material over time scales comparable with the interplanetary or interstellar passage; and (3) the entry process, i.e.: the nondestructive deposition of the biological material on another planet (Fig. 1). In the following, results from experimentation in space will be presented to test the feasibility of step two, i.e.: the impact of the space environment on the seeding of life throughout the solar system.
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