People have been dealing with questions about the origin of life throughout history - from the philosophers of Antiquity and religious thinkers to modern science. However, there is one hypothesis that can provide an answer to how life appeared on Earth.
Panspermia - translated from Greek (πανσπερμία - a mixture of all kinds of seeds, from πᾶν (pan) - "everything" and σπέρμα (sperma) - "seed") literally means "seeds are everywhere." The panspermia hypothesis states that the "seeds" of life exist throughout the universe and can move through space from one place to another. Some believe that life on Earth originated from such "seeds".
The mechanisms of panspermia include the reflection of interstellar dust by the pressure of solar radiation and the movement of extremophilic organisms in space within an asteroid, meteorite, or comet.
There are three popular variations on the panspermia hypothesis:
Lithopanspermia, or interstellar panspermia, is a hypothesis that stones ejected from the planet's surface as a result of a collision serve as a transport for biological material from one solar system to another.
Ballistic, or interplanetary panspermia, is the hypothesis that rocks ejected from the surface of a planet as a result of a collision serve as transport for biological material from one planet to another within the same solar system.
Directed panspermia is the intentional spread of the seeds of life on other planets by a highly developed extraterrestrial civilization, or the intentional spread of the seeds of life from Earth to other planets by people.
Panspermia does not explain evolution in any way and does not try to answer the question of how life arose in the Universe. This hypothesis tries to solve the mysteries of the origin of life on Earth and the spread of life in the Universe.
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History of panspermia
The first known mention of the concept of panspermia we find in the works of the ancient Greek philosopher Anaxagoras (500 BC - 428 BC), although his understanding of this idea differs from the modern hypothesis:
The first known mention of the concept of panspermia we find in the works of the ancient Greek philosopher Anaxagoras (500 BC - 428 BC), although his understanding of this idea differs from the modern hypothesis:
Anaxagoras.
In 1743, the theory of panspermia appeared in the works of the French aristocrat, diplomat and natural historian Benoit de Malier, who believed that life on Earth was "seeded" by microbes from space that fell into the ocean, and did not appear as a result of abiogenesis.
In the 19th century, the theory of panspermia was revived by scholars Jones Jakob Berzelius (1779-1848), Lord Kelvin (William Thomson) (1824-1907), and Hermann von Helmholtz (1821-1894). In 1871, Lord Kelvin stated:
In 1973, the Nobel Prize-winning molecular biologist, physicist and neurobiologist Professor Francis Crick, along with chemist Leslie Orgel, proposed the theory of directed panspermia.
Lord Kelvin.
Modern panspermia support
In 1984, during the annual US government meteor search mission, a team of scientists in Antarctica found a meteorite that broke away from the surface of Mars about 15 million years ago. The meteor was named Allan Hills 84001 (ALH84001). In 1996, ALH84001 revealed structures that could be the remains of terrestrial nanobacteria. The announcement, published by NASA's David McKay in Science magazine, made headlines around the world, and President Bill Clinton made an official statement on TV marking the event and expressing his support for the aggressive plan for robotic exploration of Mars. As a result, several tests were carried out - and amino acids and polycyclic aromatic hydrocarbons were found in ALH84001.
However, experts today agree that these substances are not an accurate sign of life and may have been formed abiotically from organic molecules or due to pollution from contact with Arctic ice. The debate continues to this day, but recent advances in nanobiological research have made this discovery interesting again.
The proof of life announcement on ALH84001 sparked a wave of support for the panspermia hypothesis. People began to speculate about the possibility of the emergence of life on Mars and its transfer to Earth on the debris of the planet that broke off after serious collisions (an example of ballistic panspermia).
Meteorite ALH84001.
In April 2001, at the 46th Annual Meeting of the International Society of Optical Engineering (SPIE) in San Diego, California, Indian and British researchers led by Chandra Wickramasinghe presented stratospheric air samples obtained by the Space Research Organization of India, which contained clots of living cells. In response to this statement, NASA's Ames Research Center expressed doubts that living cells could be present at such altitudes, but noted that some microbes could dormant for millions of years, which could probably be enough for interplanetary travel within the solar system. …
In May 2001, geologist Bruno D'Argenio and molecular biologist Giuseppe Geraci of the University of Naples announced the discovery of an extraterrestrial bacteria inside a meteorite about 4.5 billion years old. The researchers argued that the bacteria contained within the crystal structure of the minerals came to life in the cultured environment. They also stated that the bacteria possessed DNA unlike anything on Earth and survived after the meteorite was sterilized at high temperature and cleaned with alcohol. The bacteria were eventually identified as related to modern hay bacteria (Bacillus subtilis) and Bacillus pumilus, but this appears to be a different strain.
Hay stick (Bacillus subtilis).
In April 2008, world renowned British astrophysicist Stephen Hawking spoke about panspermia at the Why We Should Go Into Space lecture as part of a series of lectures at George Washington University to mark NASA's 50th anniversary.
In April 2009, Hawking also discussed the possibility of building a human station on another planet and made suggestions about why extraterrestrial life might not get in touch with the human race during the Origins Symposium at Arizona State University. The physicist also said that people can find during space exploration - like alien life as a result of panspermia, according to which life in the form of DNA particles can be transmitted through space to habitable places.
Problems and prospects of the panspermia hypothesis
A controversial scientific theory, panspermia receives either public support, indifference or criticism. For example, religious groups are critical of this hypothesis. If the theory can be proved, then the very foundations of such religions will be seriously shaken or abolished altogether. The scientific community as a whole supports this theory. Again, if it turns out to be correct, then this theory could change the way evolutionary biology is studied, as it could assume that evolution into higher life forms is genetically programmed, and this, in turn, runs counter to Darwin's theory.
Like many theories, panspermia has supporters and opponents in the scientific community. There are doubts about the survival of life upon entering the atmosphere after being in space for thousands of years, where it was exposed to cosmic radiation. However, there is no evidence that this is not possible. And even if it turns out that life came to Earth from space, modern science has no information about how it originated there.
Vladimir Guillen
