Formation of Earth's ocean and occurrence of life

Formation of Earth's ocean and occurrence of life

So far, the Earth is the only planet which life existence. Why could many lives occur on the earth? I think the occurrence of life due to the presence of water. If you are interested in the origin of life, please read it.

・Why does the Earth have an ocean?
・Ocean formation process
・Life occurrence process 

Why does the Earth have an ocean?

It is believed that the origin of the life on Earth is the sea. Other planets have almost no water in liquid state. For example, think about Venus and Mars. Venus is close to the sun, so its temperature is about 500 ° C, high temperature. At this high temperature, water cannot exist as a liquid.

On the other hand, Mars is too far from the sun, so the surface is too cold for water to exist as a liquid. Furthermore, the mass of Mars is only about one tenth of the earth, and it cannot stay the atmosphere by gravity. Because it cannot obtain the greenhouse effect by carbon dioxide, it has become an environment where it is difficult to maintain liquid water.

To summarize so far,

Heat that reaches the planet is the proper amount
The mass of the planet itself is large
 (to the extent that the atmosphere can be kept)

The above two are conditions for the presence of liquid water. The earth was a star suitable for these conditions of liquid water existence.

Ocean formation process

The Earth was formed by coalescence due to the collision of planets. In the early period, the surface was covered with magma. The activities of the earth settled down, as the surface of the earth cooled down, the water vapor remaining in the atmosphere was liquefied and the sea was made. Further cooling could have progressed so that water could not exist as a liquid, but in reality it did not.

This is because the temperature control function by the circulation of carbon dioxide worked. What is the circulation of carbon? It is a function that keeps the temperature of the earth constant. Simply put, carbon dioxide decreases as carbonate when the temperature of the earth becomes larger than a certain level, and on the other hand, when the temperature of the earth falls, carbon dioxide is released from the mantle, and it raise the temperature of the earth by its greenhouse effect. With the blessing of the three conditions, distance from the sun, the mass of the earth, and the circulation function of carbon dioxide, the sea was formed on the earth.

Life occurrence process 

How did the creature occur after the formation of the sea? In 1920, Oparin et al. in Russia proposed the theory of chemical evolution. In theory of chemical evolution, it is thought that composition of simple molecules and atoms made complex molecules gradually, and these organic matters gather and eventually form an organism.

So how did organic matter atoms happen? There are two theories. One is a theory that it was synthesized on the earth. Research shows that organic matter can be synthesized on Earth if there is carbon monoxide. Another is the theory that it comes from outer space. There is a possibility that the organic matter generated in the universe has fallen on Earth as a comet or a meteorite. Organic matter was born by either or both two way, and after that, the first life occurred in the ocean containing organic matter.

In the ocean, there is the seabed hydrothermal vent hole where hydrothermal water blows out. At sea floor hydrothermal vents, water did not boil due to pressure but kept at high temperature, and there were also many hydrogen sulfides which is a reductive gas that promotes chemical evolution. Even now, there are many primitive creatures in the hydrothermal vents, so it is considered that first living thing was generated in hydrothermal vents in the ocean floor.

This is the origin of life now considered. If there are opportunities, I will write more articles on the theme of space and life.


・The distance from the sun, 
   the mass of the earth, 
   the amount of carbon dioxide
                        were benefit for the sea in the earth

・The mechanism of life occurrence 
        is explained in the chemical evolution theory

・Life might occurred 
      around hydrothermal vents in the seafloor