Could terrestrial life be generated in outer space? The theory of panspermia It raises the cosmic origin of life.
The theory of panspermia recovers an old idea of the philosopher Anaxagoras, enunciated in ancient Greece of the s. VI a. C. But what is panspermia? The term comes from "bread" (everything) and "sperma" (seed). According to this theory, it is possible that life originated somewhere in the Universe and reached Earth embedded in the remains of comets and meteorites.
The highest defender of panspermia, the Swede Svante Arrhenius, believes that a species of spores or bacteria travel through space and can "sow" life if they find the right conditions. They travel in rock fragments and stellar dust, driven by the radiation of the stars.
The origin of life ... extraterrestrial?
About 4.5 billion years ago, in the Precambrian, the primitive Earth was bombarded by planetary remains of the young Solar System and beyond, meteorites, comets and asteroids. The cosmic rain lasted millions of years.
Comets, meteorites and star dust may contain organic matter. Organic molecules are quite common in areas of the outer Solar System, which is where comets come from. They are also in interstellar areas. Comets formed at the same time as the Solar System, and still travel through space today.
But would bacteria resist the extreme conditions of an interplanetary journey? Extreme conditions of temperature, cosmic radiation, acceleration, and surviving long enough to reach another planet? Not to mention the entrance into the atmosphere ... Experts think so.
Bacterial life is the toughest known. Bacteria that were under Arctic ice have been revived for tens of thousands of years. On the other hand, some bacteria taken to the Moon in 1967 by Surveyor 3 were revived by bringing them back three years later. And if a meteorite were large enough, the high temperature it reaches when entering the atmosphere would not affect its core.
The panspermia theory gained strength a few years ago when, when analyzing the Martian meteorite ALH 84001, fossilized bacteria appeared millions of years ago. Although we cannot know for sure if they were already there when it hit Earth. Samples of the DNA precursor molecules were also found in the Murchison meteorite.
Hard, soft and directed panspermia
Panspermia has two versions. For the natural panspermia or hard, life spreads throughout the Universe through very resistant bacteria that travel on board comets. Instead, for the molecular panspermia or soft what travels through space are not bacteria, but complex organic molecules. Upon landing on Earth they combined with the primary amino acid broth and initiated the chemical reactions that gave rise to life.
There is a variant of natural panspermia, called directed panspermia, according to which the process that "sows" life in some places of the Universe would be controlled by intelligent minds. Francis Crick, Nobel Prize and discoverer of DNA, said that life on Earth and other planets was sown by some advanced civilization. In "2001. A Space Odyssey" the sower It is a monolith that also monitors evolution. Religions also affirm that life was "created" from the outside.
Being strict, panspermia is a hypothesis, not a theory. Well, the panspermia hypothesis It seems possible, although it is not necessary to explain the origin of life on Earth. And nobody provides evidence.
On the other hand, if panspermia is correct, at this time the seeds of life would continue to travel through space and life could be sown somewhere else in the Cosmos.
Accepting the theory of panspermia means affirming that there is life outside the Earth, and this has not yet been proven. If extraterrestrial life were found in the future, it would be necessary to prove that life on Earth comes from these organisms. The theory of panspermia, for the moment, has a hard time ceasing to be a simple hypothesis; attractive and media, but nothing more.
• Are octopuses an extraterrestrial way of life?
• The Precambrian, the young Earth
• Arrhenius' dream is still alive
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