This paper takes part in the series essay competition of “great science” of Recordunkown.
The earth is a planet of life, the home of life and the home of human survival. When people walk out of the earth and see the vast universe, they know that the earth is so small. At the same time, there is a question: is there any other life planet like Earth in the universe?
In order to explore extraterrestrial life and find a life planet similar to the earth, scientists have made efforts for more than half a century. Unfortunately, so far, we have not found any extraterrestrial life, nor any living planet. There may be living planets outside the solar system, but within the solar system, there is only one living planet like the earth. So scientists began to think about a new question: what conditions do planets need to have life?
It is not so simple as luck that the earth can become a life planet with rich species. It must be something that we didn’t know happened in the early formation period. Under various effects, the earth has the conditions for the birth of life. Scientists speculate that a planet may need water, carbon, enough light and heat to give birth to life. The environment on the planet’s surface should not be too hot or too cold. Gravity should also be moderate. At the same time, there should be an appropriate atmosphere.
However, a new study by scientists adds another important factor to the reason why planets can give birth to life: moderate intensity asteroid and comet impacts. One may wonder: why do planets have to go through the right asteroid and comet impacts to give birth to life? Without their impact, a planet in the habitable zone would not be able to give birth to life?
In this regard, scientists put forward a new research point of view. The reason why they think that the impact of asteroids and comets is so important is that the impact can effectively improve and perfect the planet’s ecosystem and make it a more suitable planet for the birth of life. There are two main reasons.
The first reason is that when a larger object hits a planet, two things happen. 1、 The material on the object will be added to the mass of the planet; second, part of the atmosphere around the impact area will float into space. One might say, isn’t it a bad thing that part of the planet’s atmosphere is stripped off? How can it be a good thing now? Here we have to talk about the truth that extreme things must be reversed. Everything needs an appropriate degree to be a good thing. If it is too extreme, it will turn a good thing into a bad one.
The planet’s atmosphere is the same. If it is too thick, it is not conducive to the birth of life. For example, the atmosphere of Venus is much thicker than that of the earth, so that Venus is covered by a thicker atmosphere, resulting in higher surface temperature. At the same time, too thick atmosphere makes its surface atmosphere stronger, which is unfavorable for the birth of life.
The second reason is that the impact of celestial bodies can change the composition of the atmosphere? Scientists say there must be some “volatile matter” in the planet’s atmosphere to be able to give birth to life. Volatile substances refer to the chemical substances that can boil at low temperature, such as water and carbon dioxide. All life we know needs certain water and carbon to survive. Scientists believe that due to the characteristics of these chemical substances, life is indispensable anywhere in the universe.
But not all planets start with enough concentrations of volatile matter. Stars are much brighter when they are young than later, and the heat is enough to scorch all the floating dust in the habitable zone. After these floating dust form planets, they need to obtain these volatile substances from other places. In other words, they have to collide with some larger objects “wandering” in the universe.
Scientists have found that asteroids and comets with diameters ranging from 20 meters to 1 kilometer can provide a large amount of volatile matter for planets, and add more atmosphere to planets than they take away. Through the impact of asteroids and comets, the atmosphere of the planet can maintain a suitable thickness, and at the same time, it can add more “volatile substances” to the atmosphere. These volatile substances are important substances for the birth of life, with which life may be born.
When the earth was just formed, it was hit by many asteroids and comets, which not only brought rich minerals to the earth, but also made the earth’s atmosphere have more volatile substances. At the same time, part of the earth’s atmosphere was stripped away, and the thickness reduction was beneficial to the birth of life.
More importantly, the impact of comet has brought a lot of water resources to the earth, and water is the source of life. With a large amount of water resources and active carbon and other active substances in the atmosphere, the earth slowly gave birth to life. Through step-by-step evolution, the present life world and human civilization came into being. Through these new researches and explorations, it is of great help for human beings to search for extraterrestrial life in the future.
In fact, when scientists are looking for possible living planets outside the solar system, their important exploration goal is to have a similar environment to the solar system. First, there should be stars like the sun, and second, there should be earth like planets very similar to the earth. The birth of life on earth is closely related to the sun.
As a result, galaxies formed by stars of the same mass as the sun outside the solar system have more possibilities for the birth of living planets. Because only stars like the sun have long enough lives to reach about 10 billion years. Only if the life of a star is good enough, can it have enough time to breed a living planet. It takes a long time to know the birth and evolution of life on a planet. At least a few hundred million years, at most a few billion years.
If a star doesn’t have a long enough life span, when a planet is about to give birth to life, the life span of the star will expire, expand to a red giant, and then collapse inward, resulting in a supernova explosion. The planet that has the hope of giving birth to life will eventually be devoured and destroyed. Therefore, the search for stars as massive as earth is an important factor in the search for extraterrestrial life and civilization.
Some people may say that if stars with smaller mass than the sun live longer, will the galaxies that form have more living planets? In fact, it is not. If the mass of a star is smaller than that of the sun, it is a red dwarf star. This kind of star is darker and cooler. Its habitable zone needs to be closer to the main star. If it is too close to the sun, asteroids and comets will fly much faster, and the impact on planets will be more violent, which will cause a lot of loss of planetary atmosphere.
As we said earlier, a small amount of loss of planetary atmosphere is conducive to the birth of life. However, if the impact is too violent and causes the loss of planetary atmosphere, the foundation and conditions for the birth of life will be lost. It can be seen that the appropriate mass of stars is also crucial for the birth of living planets.
The birth of a living planet needs to meet many conditions. Without any conditions, it may not be possible to produce a living planet like the earth. Of course, the universe is vast and vast, and the requirements of the environment for the birth of life will be different. It is possible that some life can be born without meeting many conditions.
Although it is possible to give birth to life under insufficient conditions, it is difficult to give birth to intelligent life like human beings. Scientists’ current exploration of the solar system speculates that there may be life on several moons of Jupiter and Saturn, and even on Mars. But there is no possibility of intelligent life on these planets. The reason is that they do not fully meet the conditions for the birth of life. Only a few of them have met the conditions. Although simple life may be born, it is unlikely that intelligent life like human beings will be born.
Therefore, scientists are looking for civilized planets that may exist outside the system, and the focus is to find planets that are very similar to the earth. Our earth, standing in space, even hundreds of millions of kilometers apart, although we see only a grain of dust, it is also a blue dust. This kind of beauty and unique style may be the symbol of advanced life planet or civilized planet.
Those planets in the universe with the same beautiful color as the earth are likely to give birth to life, and may have the possibility of intelligent life. In other words, these beautiful exoplanets may also be civilized planets. Of course, beautiful planets that are very similar to earth are very rare.
Through the exploration and discovery within 1000 light-years of the earth, scientists have only found a few planets that are very similar to the earth. They also have the beauty of the earth. The number of earth like planets in the range of 1000 light-years may be too large to be estimated. It can be seen that there are many earth like planets in the universe, but there are very few beautiful earth like planets. It also shows that even if there are other civilized planets in the universe, they will be rare.
Of course, how do scientists understand the formation of life on earth? There are still a lot of puzzles. The impact of asteroids and comets on the early earth can not be completely determined. More exploration and efforts are needed to solve the mystery of the birth of planets. We are looking forward to that day.
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