We all know that the earth is a blue planet of life. The reason why it appears blue is that there are a lot of water resources on the surface of the earth, and water is the source of life. It is the earth with a lot of liquid water, there will be behind the birth of life, the birth of mankind.
The survival of life on earth cannot do without water, so where did the water of the early Earth come from? There are two theories about the source of the earth’s water. One is that it comes from the earth itself. During the early formation of the earth, a large amount of hydrogen and oxygen were released from the earth’s interior. Coupled with the particle flow from the sun, a large amount of hydrogen and oxygen appeared on the earth. These substances mixed together and had a chemical reaction, resulting in the formation of water.
Another view is that the earth’s water may come from comets. In the early days of the earth, comets hit the earth and brought a lot of water resources to the earth, making the earth a world full of liquid water. Both theories have some theoretical basis, but most scientists agree with the second one, that is, the earth’s water is brought by comets.
For comet, I believe that every astronomer is not unfamiliar, it is a beautiful landscape in the universe. Comet in the folk will also be a name called “broom star”, the reason is that it has a long tail. When comets pass through the earth, we can see the long tail of comets through telescopes, which is the unique feature and beauty of comets.
The length of the comet’s tail is amazing. It’s at least several million kilometers long, and some even hundreds of millions of kilometers long. Some people may say that if a comet has such a long tail, it must be very big. In fact, it’s not like that at all. The body of the comet is at the front end of the tail. It’s actually a small star with a diameter of no more than five kilometers, Even smaller comets are only a few hundred meters in diameter.
So why does such a small comet have such a long tail? This is mainly related to the materials that make up the comet. The small stars that make up the comet are all made up of water ice and dust. When it moves forward rapidly, it will emit water vapor, which will fall behind the comet and form a long comet tail under the sunlight.
So where do these spectacular comets come from? For the origin of comets, scientists believe that there are mainly three places. One is the asteroid belt between Mars and Jupiter, where there are no less than 100000 asteroids, including comets. Another source is the Kuiper belt on the edge of the solar system, where there are too many asteroids and other celestial bodies to be estimated, and there are many comets in it.
The last place is the outer part of the solar system, the Oort nebula. The Oort nebula is the most mysterious and unpredictable place in the solar system. Its diameter can reach 2 light-years, and it is the outer shell of the solar system. In such a vast area, although the material distribution is sparse, the number of celestial bodies can not be estimated because of its large range. There are comets entering the planets in the solar system Part of it could have come from here.
Some people may wonder: why comets can only be produced in these remote places, but not in the habitable zone? In fact, this is not difficult to explain. As we all know, the main material of comets is water ice. But in the habitable zone, because it is close to the sun and the temperature is high, it is difficult to have free water molecules, let alone water ice.
Only outside the habitable zone, the farther away from the sun and the lower the temperature, can a large number of water molecules exist in the space and form water ice. These ice crystals and dust condense together to form stars, forming unique small objects such as comets.
Through the observation of the Kuiper belt on the edge of the solar system, scientists found that there are a lot of ice crystals on the surface of many celestial bodies here, which also confirms the scientists’ prediction. It also shows that it is very difficult to have free water molecules in the inner solar system, especially in the habitable zone, so it is extremely difficult for planets in this range to form a large amount of water resources.
That’s why scientists are more inclined to be brought by comets for the source of a large amount of liquid water on the earth. When the early Earth was formed, the temperature of the sun was even higher than now. At that time, the earth was a very hot planet, and it was basically impossible to form water by itself. Later, after the formation of the earth stabilized, there was no stable water molecules around the earth, let alone falling to the earth to form water.
At this time, the solar system was not very stable because it had just formed. Many objects on the edge of the solar system broke away from their orbits and flew to the inner galaxy, including comets carrying a lot of water ice. Finally, the comet hit the earth, leaving a large amount of water ice, and the earth is a warm planet. Some of the water ice left in the atmosphere to form a rain layer, and some fell to the ground to liquefy and form the ocean.
Comets that entered the solar system in the early days not only hit the earth, but also Venus, Mars and other celestial bodies. Therefore, scientists suspect that Venus and Mars may have liquid oceans in the early days, but later they lost the water because they did not know what kind of disaster happened. In addition to a large amount of water on the earth, there is also a large amount of frozen water on the surface of many moons of Jupiter and Saturn, which may contain more water than the earth.
Scientists speculate that several satellites of Saturn and Jupiter that contain a lot of water resources may be comets that entered the planets in the solar system in the early days. When they passed through Jupiter and Saturn, they were captured by strong gravity and became satellites.
Comets bring water resources to the earth, which makes it possible for the birth of life. Therefore, we should thank comets for bringing vitality to the earth. Otherwise, the earth may be a barren, lifeless planet, and there will be no human beings. Now comets are very rare, because the solar system is already a very stable galaxy. Now these comets have their own orbit, only when they move close to the earth, we can see its beautiful and spectacular scene.
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