Panspermia

Panspermia (from Ancient Greek πᾶν (pan) 'all' and σπέρμα (sperma) 'seed') is the hypothesis that life exists throughout the Universe, distributed by space dust,^[1] meteoroids,^[2] asteroids, comets,^[3] and planetoids,^[4] as well as by spacecraft carrying unintended contamination by microorganisms,^[5][6][7] known as directed panspermia. The theory argues that life did not originate on Earth, but instead evolved somewhere else and seeded life as we know it.

Panspermia comes in many forms, such as radiopanspermia, lithopanspermia, and directed panspermia. Regardless of its form, the theories generally propose that microbes able to survive in outer space (such as certain types of bacteria or plant spores^[8]) can become trapped in debris ejected into space after collisions between planets and small solar system bodies that harbor life.^[9] This debris containing the lifeforms is then transported by meteors between bodies in a solar system, or even across solar systems within a galaxy. In this way, panspermia studies concentrate not on how life began but on methods that may distribute it within the Universe.^[10][11][12] This point is often used as a criticism of the theory.

Panspermia is a fringe theory with little support amongst mainstream scientists.^[13] Critics argue that it does not answer the question of the origin of life but merely places it on another celestial body. It is also criticized because it cannot be tested experimentally. Historically, disputes over the merit of this theory centered on whether life is ubiquitous or emergent throughout the Universe.^[14] Due to its long history, the theory maintains support today, with some work being done to develop mathematical treatments of how life might migrate naturally throughout the Universe.^[15][16] Its long history also lends itself to extensive speculation and hoaxes that have arisen from meteoritic events.