How did life on the Earth arise: three fascinating theories

Planet Earth was formed about 4.6 billion years ago. It was probably too hot and unsuitable for life forms at first, so the question of what led to their appearance still worries scientists.

Science does not give a definitive answer, but it offers several fascinating theories. National Geographic told us about the most likely ones.

It is not known for certain how, but it is a fact that after a billion years, life formed on a hot planet that was regularly bombarded by asteroids. It left evidence of its presence in the form of fossilized microbial mats.

1. Lightning

Atmospheric conditions on Earth at the time when life appeared were very different from those that exist today. Back in the 1950s, Nobel Prize-winning chemist Harold Jury noted that most atmospheres in the solar system are dominated by nitrogen and methane, and suggested that Earth also had this type of atmosphere. But later, it was the presence of life that saturated it with oxygen.

Jüri then also thought that the early atmosphere might have been very efficient for creating organic compounds, so he commissioned his research student Stanley Miller to design an experiment to test this theory.

A closed system was created in which water was heated and combined with hydrogen, methane, and ammonia molecules. They were then short-circuited by an electric current (like lightning) and cooled to allow the mixture to condense and fall back into the water like rain.

The results were impressive. Within a week, the experimental "ocean" turned reddish-brown as molecules combined to create amino acids, which are the building blocks of life.

2. Space

According to another theory, amino acids, as well as some other key building blocks of life, such as carbon and water, could have come to the early Earth from space. Comets and meteorites have been found to contain these trace elements, so this theory may contain a kernel of truth.

According to Nobel Prize-winning chemist Jack Shostak of the University of Chicago, an early atmosphere of nitrogen and carbon dioxide would have been less favorable for some of the proposed chemical reactions that took place in the Miller-Jury experiment. Instead, the asteroid impact could well have created atmospheric hydrogen and methane, which would have temporarily created favorable conditions for the formation of compounds necessary for life.

3. The ocean

Another theory suggests that life could have originated deep in the ocean, around hydrothermal vents. However, Jack Shostak rejected this hypothesis because ultraviolet radiation is necessary for some stages of nucleotide and RNA formation. Therefore, they could not be formed deep in the ocean, where sunlight does not reach.

However, the first life likely formed in water because chemical reactions require a solvent. It didn't happen at the bottom of the ocean but on the surface. Perhaps in shallow ponds or hot springs.

In addition, scientists suggest that life could have arisen several times, in different ways, but it was destroyed by asteroids or failed to develop sufficiently. This went on until the RNA-based molecule, which is the ancestor of all of us, took hold.

If this is true, then we will never know how the very first life on Earth appeared, because it left no traces.

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