Exogenesis ("outside origin") is a hypothesis that proposes life on Earth was transferred from elsewhere in the Universe. Panspermia is similar but hypothesises that seeds ("sperma") of life are general throughout the Universe.
Sir Fred Hoyle and Chandra Wickramasinghe were supporters of the hypothesis and further contended that lifeforms continue to enter the Earth's atmosphere, and may be responsible for epidemics, new diseases, and the triggers for evolutionary spurts.
Imperial College, London scientists have confirmed for the first time that important components of early genetic material, including uracil and xanthine, found in meteorite fragments are extraterrestrial in origin.
 See also
- Wikipedia's article on panspermia.