Among the numerous meanings of panspermia is free roaming of seeds. Scientifically, it is the roaming of life baring forms contained in debris of universe bodies such as comets. Panspermia hypothesis states that the life forms are transferred to various universe bodies through meteorites, comets and asteroids. Various theories of panspermia claim that life on earth originated from seeds of life reaching our planet from space either on meteorites or as spores pushed by solar radiation (Impey, 2010)
This hypothesis as first proposed by Svante Arrhenius who suggested that living microorganisms in a dehydrated state could have been driven here by the pressure of light from the star of another planetary system (Zubay, 2000) They include Ballistic panspermia suggesting that impact between the roaming bodies expelled rocks from a planet’s surface serving as transfer avenues for spreading dormant biological material from one planet to another within a similar solar system.
A second variation Lithopanspermia involves expelling of materials from one solar system to another. The only difference from the first one is the area of transfer. A third variation of the hypothesis, directed panspermia, suggests that there was intentional spreading of the free roaming material of life from planet earth to another through advanced extraterrestrial civilization. In this third case, humans were the sole transfer agents.
This hypothesis, however does not detail the evolution concept and only touches on the origin of life on planet earth and transfer of life throughout the universe. It should be noted that these processes are time bound. In this regard, panspermia hypothesis still holds but due to the massive range of time the process takes, it is impossible to observe the processes in one’s lifetime.
There are two possibilities where the hypothesis applies. It may occur between star systems or between planets. The free roaming seeds are transported either through radiation pressure or as microorganisms in rocks composing the free roaming bodies. Evidence of hypothesis exists in study of meteorites found on planet earth.
Astrobiologists’ studies of extremophiles indicate that such organisms can survive severe conditions until the time when life supporting conditions are available in the areas of existence. These bacteria gave rise to beginning of life on planet earth once the conditions on the planet could support life.
Due to adaptability of bacteria in certain conditions, it is possible to have survived in dormant state for several million years. Possible shelters from these extreme conditions can be thick meteoroid or icy comets. The studies are carried out by duplicating harsh conditions that are conceived to have existed and then projecting the findings against time to establish whether the bacteria could truly survive.
Spores are another type of these seeds that survive inhospitable and extremely harsh environments. The structural form of spores that form the life cycle of some algae and fungi are highly resilient to ultraviolet and gamma radiations. The spores stay in an inactive state until conditions that favor germination sweep across regardless of time taken. Space borne organic molecules and structures have been found in meteorites (NASA, 2009). The report is based on an astonishing discovery of a strain of amino acid that is one of primary chemical building-blocks of basic life after analysis of the comet rocks.
According to Lurquin (2003) bacteria spores drifted through space, landed by chance on earth, germinated and started the process of evolution. This was an interesting idea and it solved the problems of origin of life on Earth.
Although there are different variations of the hypothesis, the meaning is that it attempts to explain the beginning of life on earth.
References
Impey. (2010). Talking about life. Cambridge: Cambridge University press.
Lurquin, F.P. (2003). The origins of life and the universe. Cambridge: Cambridge University press.
NASA Life building-block report (2009). Chemical building-blocks in a comet.
Zubay, L.G. (2000). Origin of life on Earth and the cosmos. Massachusetts: Academic Press.