Ancient micronauts: interplanetary transport of microbes by cosmic impacts

Recent developments in microbiology, geophysics and planetary sciences raise the possibility that the planets in our solar system might not be biologically isolated. Hence, the possibility of lithopanspermia (the interplanetary transport of microbial passengers inside rocks) is presently being re-evaluated, with implications for the origin and evolution of life on Earth and within our solar system. Here, I summarize our current understanding of the physics of impacts, space transport of meteorites, and the potentiality of microorganisms to undergo and survive interplanetary transfer.