The panspermia theory argues that life is originated in space, in spatial ices, and continuously distributed to the planets by comets and meteorites. The origin could be somewhere nearby, like Mars, or light years away.
The fifth-century BC Greek philosopher Anaxagoras first wrote about Panspermia. It assumed a more scientific form in 1834 through the proposals of Jöns Jacob Berzelius, Hermann E. Richter (1865), Kelvin (1871), and Hermann von Helmholtz (1879). The first detailed hypothesis was made in 1903 by Swedish chemist Svante Arrhenius, the father of physical chemistry. Arrhenius proposed radiopanspermia, that microscopic forms of life can be propagated in space, driven by the radiation pressure from stars.
Man used to speculate on the origin of matter, but gave that up when experience taught him that matter is indestructible and can only be transformed. For similar reasons we never inquire into the origin of the energy of motion. And we may become accustomed to the idea that life is eternal, and hence that it is useless to inquire into its origin.Svante Arrhenius
- that those organic molecules originated in space
- that life originated from these molecules, extraterrestrially
- that this extraterrestrial life was transported to Earth
In 1974, Fred Hoyle and Chandra Wickramasinghe proposed the hypothesis that some dust in interstellar space was largely organic (containing carbon), which Wickramasinghe later proved to be correct. Hoyle and Wickramasinghe further contended that life forms continue to enter the Earth’s atmosphere, and may be responsible for epidemic outbreaks, new diseases, and the genetic novelty necessary for macroevolution. Lithopanspermia is the transfer of organisms in rocks from one planet to another through interplanetary or interstellar space, such as in comets or asteroids.
- Planetary ejection – For lithopanspermia to occur, microorganisms must survive ejection from a planetary surface, which involves extreme forces of acceleration and shock with associated temperature excursions.
- Survival in transit – The survival of microorganisms has been studied extensively using both simulated facilities and in low Earth orbit. A large number of microorganisms have been selected for exposure experiments, both human-borne microbes (significant for future crewed missions) and extremophiles.
- Atmospheric entry – to test whether microbes on or within rocks could survive hypervelocity entry through Earth’s atmosphere. Tests could use sounding rockets and orbital vehicles.
The most likely origin for pre-evolved life forms is Mars, which is now believed to have previously been habitable. According to the Panspermia theory, Mars was not only habitable but sustained life during a period that overlapped with Earth’s early days of habitability.
If a meteor struck Mars with enough force, such as the force of the meteor that struck Earth forming the Moon, it might have caused Martian debris to fly into space. Martian microorganisms living in that space debris may have survived the journey, landing on Earth and taking root on its newly habitable surface.
- Anaxagoras was a Pre-Socratic Greek philosopher. Born in Clazomenae at a time when Asia Minor was under the control of the Persian Empire, Anaxagoras came to Athens. According to Diogenes Laërtius and Plutarch, in later life he was charged with impiety and went into exile in Lampsacus; the charges may have been political, owing to his association with Pericles, if they were not fabricated by later ancient biographers. He also gave a number of novel scientific accounts of natural phenomena, including the notion of panspermia that life exists throughout the universe and could be distributed everywhere. He deduced a correct explanation for eclipses and described the Sun as a fiery mass larger than the Peloponnese, as well as attempted to explain rainbows and meteors.