In urgent need of information about the origin of life, I hope everyone can help~~

The origin of life is an eternal mystery. When and where did life on earth originate? How did it come about? For thousands of years, people have encountered many traps while solving this mystery, and at the same time they have also seen unprecedented light. In the theory of the origin of life, the first mystery is the time of the origin of life. The second is the issue of the origin of life. How did life originate? Where did it originate?

Since ancient times, there have been many theories to explain the origin of life. Such as the Western creation theory, the Chinese Pangu theory of the creation of the world, etc. But it was not until the 19th century, with the publication of Darwin's "On the Origin of Species", that biological science underwent unprecedented changes. At the same time, it also brought a glimmer of light to mankind's unraveling of the eternal mystery of the origin of life. This is the modern Chemical Evolution. The chemical evolution theory of the origin of life was first confirmed by an American scholar Miller in 1953. What should the events of the origin of life look like when Miller described it? That is, in the early days, the earth contained a large amount of reducing primitive atmosphere, such as methane, ammonia, water, hydrogen, and primitive oceans. When lightning on the early earth polymerized these gases into a variety of amino acids , and these various amino acids, under normal temperatures and pressures, may be locally concentrated and further evolve into proteins and other polysaccharides, as well as polymer lipids. At a certain time, they may be fertilized into life. This is Miller describes the evolution of life.

Life on earth may have originated between 3.8 billion and 4 billion years ago, but we should clearly understand that we are still a long way from unraveling the ancient mystery of the origin of life. scientific process. The evolution from inorganic matter to organic matter, to organic compounds to organic life forms, also involves many accidents. It is not that there is such an environment and such formation conditions that life can be produced. Someone once said that these inorganic substances are like a garbage dump with everything in it, including plastics, plastic bottles, iron, scrap metal, and oil. Life, a single cell, is like a beautiful Mercedes-Benz. After a typhoon, These pieces of junk are assembled into a Mercedes Benz. Therefore, we can imagine that the process of the origin of life was very, very difficult. Therefore, maybe we are on this blue planet, which is the only paradise for life, so please protect our earth and cherish life on earth. We cannot expect a second origin of life on earth.

In the medieval West, the theory that God created all things in seven days as described in the Bible was also very popular. Today, it seems that the origin of life is not as described in these ancient legends or myths, but it shows that mankind has devoted great enthusiasm and attention to the mystery of the origin of life for a long time. But how should the origin of life occur? How does science explore this eternal mystery? What progress have we made? What issues remain unresolved? This is what I want to introduce to you today.

First of all, the first mystery of the theory of the origin of life is the time of life, the time of origin. In the medieval West, people had no doubts about the story of God’s creation of man in the Bible. In 1650, an Irish archbishop calculated that the exact time of God’s creation was 4004 BC based on the description in the Bible. , and another priest even calculated the creation time more accurately to nine o'clock in the morning on October 23, 4004 BC. In other words, the origin of life was six thousand years ago. This is of course not true, but what is it really? It’s really just a scientific answer. How does science answer the time of the origin of life? That means answering with fossils, fossils preserved in rocks. We know that after organisms die, their remains are preserved in rocks under appropriate conditions. We call them fossils. The rock formations formed in geological history are like a chronicle. The evolutionary history of the earth's creatures is deeply buried in these rocks. The older the biological fossils are, the lower layers of the rock formations are preserved.

The oldest biological fossils we have discovered so far are rocks from Western Australia about 3.5 billion years ago. These fossils are similar to today's cyanobacteria, which are some primitive life. It is invisible to the naked eye. Its size is only a few microns to dozens of microns, so we can say that life originated no later than 3.5 billion years ago.

At the same time, we know that the earth was formed about 4.6 billion years ago. With these two data, we can see the age of the origin of life, which can be roughly defined as between 4.6 billion and 3.5 billion years. Today, with the development of science, geologists believe that in the early days of the earth's formation, the earth was hit by a large number of asteroids and meteorites, and it was not suitable for the survival of life. Rather than saying that there was life on the earth at that time, it would be better to say that it was destroying life. Therefore, the origin of life on the earth was no earlier than 4 billion years. In addition, carbon was found in 3.85 billion-year-old rocks in Greenland. As for this carbon, we know that there are two types of carbon, one is inorganic carbon and the other is organic carbon. In addition, this carbon is divided into heavy carbon and light carbon, so we can speculate on the source of these carbons based on the ratio of light carbon to heavy carbon in this carbon. Based on carbon isotope analysis, scientists speculate that this carbon is organic carbon and comes from living organisms. In other words, in this way we have greatly shortened the time when life originated, that is, between 4 billion and 3.8 billion years ago. Since the origin of life on the earth, up to 4.5 billion years ago, life has been endless. Evolutionary history.

Well, first of all, we now have a concept of the origin of life, which is between 4 billion and 3.8 billion years ago. How did life originate? Where did it originate? In this way we have to review some hypotheses about the origin of life.

The first is the theory of creation. In the first chapter of the Old Testament, it is written that God created everything in the world in seven days. In the West in the Middle Ages, this concept was generally accepted. It is said that this concept is still accepted by many people until now, but of course this is not true. The second one is the theory of autogenesis. For example, the Greeks believed that insects are born in the soil, and everything is renewed in spring. Seeds germinate from the soil, and insects emerge from the egg shells left last year. But this is not the origin of life, but the continuation of life. It can be said that this autogenesis theory has now been completely abandoned. Similar to this statement, for example, the Egyptians believed that life came from the Nile River, and in ancient China there was also a saying that rotten grass gave birth to fireflies.

The third hypothesis about the origin of life is panspermia, which was also quite popular in the West in the 19th century. Panspermia believes that life is inherent in the universe. You have to ask me about life. Where does it come from? First, answer a question for me: How did the universe originate? Where did matter come from? You have given me an answer about where matter comes from, so I can say where life comes from. In fact, this is agnosticism. In the second half of the 20th century, panspermia gradually developed into the current theory of panspermia. Until now, many scientists believe that the formation of enzymes, like proteins, and genetic material necessary for life takes hundreds of millions of years. There was not enough time in the early Earth to complete these processes. Because it is 200 million years old, they believe that life must have come to the earth from somewhere in the universe in the form of spores or other life forms. This concept also has a certain basis.

Since the 1940s, humans have used astrophysics methods to detect nearly a hundred kinds of organic molecules outside the earth, such as formaldehyde, amino acids, etc. Two of the celestial bodies can be related to life on the earth. They may bring life or organic molecules to the earth. One is a comet and the other is a meteorite. We know that these two celestial bodies contain a large number of organic molecules. For example, we call some comets dirty snowballs. They not only contain solid water, but also amino acids, iron, ethanol, purine, pyrimidine and other organic compounds. Life may have been produced on comets and brought to the earth. Or when comets and meteorites hit the earth, new life is produced from these organic molecules through a series of synthesis. Of course, there are different concepts in this panspermia theory. It has two fatal weaknesses. One is whether life can migrate in the universe for a long time? Can it still survive? We know that the distance between celestial bodies is measured in light years, and communication between celestial bodies may take thousands of years to travel from one planet to another. So in this kind of vacuum, exposed to this large amount of cosmic rays, can living life continue to sprout for millions of years? This is the biggest problem. The second is the process from inorganic molecules to organic compounds. This process, for example, we see the formation of small organic molecules on comets, can also be formed on the earth. There is no doubt about it.

In 1859, with the publication of Darwin's "The Origin of Species", biological science underwent unprecedented changes, and it also brought a glimmer of light to mankind's unraveling of the eternal mystery of the origin of life. This is the modern theory of chemical evolution. The chemical evolution theory of the origin of life was first confirmed by an American scholar Miller in 1953. Since you said that the temperature of the early earth was relatively high and filled with a lot of reducing gases and water, then I will put these Gas, put water in a bottle and see if it can't produce life, or produce organic compounds. In 1953, Miller put ammonia, hydrogen, water, and carbon monoxide into a sealed bottle, inserted metal rods at both ends of the bottle, and turned on the power supply. Through this lightning-like effect, it did indeed occur within a few days. A large number of amino acids are then produced. That means that on the earth, under lightning and at normal temperature, it can also become inorganic molecules and synthesize organic molecules. We know that amino acids are the most important substances that make up proteins. It can be said that they are the most important substances that make up the origin of life. So, what should the events in Miller's description of the origin of life look like? That is, in the early days, the earth contained a large amount of reducing primitive atmosphere, such as methane, ammonia, water, hydrogen, and primitive oceans. When the lightning action on the early earth aggregated these gases into many A variety of amino acids, and these various amino acids, under normal temperature and pressure, may be locally concentrated, and then further evolve into proteins, proteins and other polysaccharides, as well as polymer lipids, which may become pregnant women at a certain time. Life, this is the process of life evolution described by Miller.

However, this kind of warm pool theory also encounters some problems, including two problems. The first problem is that geologists now believe that the early atmosphere of the earth did not contain a large amount of reducing gases. , which contains a large amount of carbon dioxide and nitrogen, and is more inert than Miller's gas. In the case of lightning, you don't form large amounts of amino acids. Second, warm pools could not form for a long time in the early Earth. Why? Because the earth was in its early stage at that time, as I just said, it had a large number of meteorites, meteors, and the radioactivity of the earth itself, and the temperature was very high. Once life was born in your warm pool, and a meteorite came over, the temperature could reach thousands in an instant. Degrees, or even thousands of degrees, life has become extinct, and the origin of life can only come again. But that’s what we think about now. Are there relatively high temperatures, reducing gases, and biological existence on the earth today? Well, there are two works that can be said to be of epoch-making significance. One is the American scholar Blake in 1967, who discovered a large number of thermophilic organisms in the hot springs of Yellowstone Park. We know that proteins generally solidify if they exceed 60 degrees. Boiled eggs are cooked when the temperature is above 60 or 70 degrees, but can living things still live at temperatures above 60 degrees? It was unthinkable before.

The second one is Chris in 1977. He also discovered a large number of thermophilic microorganisms in the hot springs at the bottom of the Pacific Ocean. The temperature is higher, it may reach 200 to 300 degrees. . Its pressure is between 200 and 300 atmospheres. What is its environment like? It does have a large amount of reducing gases, including hydrogen sulfide, methane, hydrogen, and carbon monoxide. This environment is indeed very similar to the environment of the early earth four billion years ago. So did the origin of life occur at this time? Woolen cloth? This is what we see now, but are there any microorganisms found in volcanic vents or hot springs among the fossils? Indeed, in this regard, we have also made very important progress in fossils. For example, in 2000, Rosmassen, an Australian scientist, discovered in volcanic deposits in Australia that are about 3.2 billion years old. A large number of well-preserved filaments. This shows that 3.2 billion years ago, life existed in large numbers near hot springs. This is now the latest, most popular, and can also be said to be the most scientific hypothesis about the origin of life so far, that is, life originated from hot springs. Or near the submarine hot springs, commonly known as "black smokers."

Undersea hot springs and hot springs on land have many different characteristics. The first one is high temperature. Second, it contains a large amount of reducing gases. In addition to carbon dioxide, there are also carbon monoxide, hydrogen, ammonia and hydrogen sulfide.

The third characteristic is that they all contain a large number of organisms, such as cyanobacteria, photosynthetic bacteria, and sulfur bacteria. In particular, a type of archaea thrives abnormally at high temperatures. It flourishes in large numbers when the temperature exceeds 100 degrees. For example, as soon as the temperature drops, it will go into dormancy and cannot live normally. So do these creatures represent the earliest and most primitive life forms when life on earth originated? ?

The temperature of the first early earth was very high, and the earliest life forms produced should be organisms that could adapt to high temperatures, and the organisms in hot springs were exactly thermophilic microorganisms. Second, the environment of hot springs has many similarities with the environment of the early Earth. For example, it has high temperatures and a large amount of reducing gases, carbon monoxide, hydrogen, ammonia, hydrogen sulfide, etc. Third, in a high-temperature hot water environment, it is conducive to the dehydration of small-molecule organic compounds and their polymerization into organic polymers. For example, if we now use organic small-molecule amino acids to synthesize proteins, it is in hot water through This thermal polymerization reaction forms such a polymer after dehydration, especially near the hot water outlet, forming pyrite, commonly known as "fool's gold". It is composed of sulfur and iron. On its surface, it is very conducive to the synthesis of polymers, because the iron sulfide surface is a very good natural catalyst. The fourth favorable evidence is that there is a gradient of temperature and water chemistry between the hot spring mouth and the outer seawater. This gradient is also conducive to the continuous reflection of various chemicals. We know that when the hot spring mouth erupts , its temperature may reach 200 to 300 degrees, especially near the mid-ocean ridge of the seafloor. As for the temperature of seawater, the temperature of this seafloor is generally 0 to 4 degrees. In this case, it ranges from 300 to 400 degrees. , it has a temperature gradient. If this temperature gradient is used, it can be said that there is a continuous reflection for the synthesis of organic compounds. The fifth and most important point is that the creatures in hot springs are indeed the most fundamental type of biological evolution speed, which means that their genes are the oldest type.

A modern biologist, through biomolecular research, compared the genes of some thermophilic archaea in hot springs with common bacteria today, and found the similarities in their genes. No more than 60%. This means that these archaea contain a lot of ancient genes, which means that they are likely to be of this type at the origin of life. It should be said that the best evidence for the origin of life when we study it is the information contained in rocks and fossils on the earth between 4 billion and 3.8 billion years ago. However, after 4 billion years of changes, the earth has changed beyond recognition. Even if you have rocks that are 4 billion to 3.8 billion years old, the current earth has entered a large number of variants and there is almost no information.

Therefore, we should not limit our attention to the earth. If life is a common phenomenon in the universe, is there something similar to the early earth on other celestial bodies besides the earth? What about the environment? If so, it may open a new window for studying the origin of life. What is our first target? It is not Mars but the moon. Now geologists believe that the moon was erupted from the earth when a large planet hit the earth 4 billion years ago. The current moon was formed exactly 4 billion years ago. If there was an origin of life on the earth, wouldn't it be a solution to this problem if we look at it on the moon? In ancient Chinese mythology, there is the saying of Chang'e flying to the moon. There are laurels and moon rabbits on the moon, and there are also romantic love stories. However, from the 1960s to the 1970s, with the aerospace exploration of the former Soviet Union and the United States, With the successful landing of astronauts, this myth was completely shattered. The moon is actually a desert star with no life, no water, no oxygen, and is not suitable for life.

So what is our second goal? The second target is Mars, because Mars may have had a similar experience to the Earth 4 billion years ago. The material composition of Mars is very similar to the Earth, and its orbit is also very similar to the Earth. So is there life on Mars? What are we going to do on Mars? When we look for the origin of life, where should we start? Generally speaking, there are three points. The first one is to search for whether there is living life on Mars? If there is living life, that's fine. If so, life may have really originated in the universe, or the creatures on earth may have come from Mars or other comets.

Secondly, we look for liquid water, because we know that water is the source of all things and water is the source of life. The life forms we understand on earth today are inseparable from water, so looking for liquid water is also a very important indicator. The third one is looking for compounds related to life. If we don’t have living creatures now, were there any in the past? Did organisms in the past form some compounds? Is it preserved as a fossil in these rocks? So we go to Mars to search for life with three purposes.

When the American Viking spacecraft sent information back to Earth in 1957, there was no life on Mars and no liquid water. It was a barren and thirsty red planet. But mankind has not been discouraged. In the 1990s, NASA increased its exploration of Mars, using images obtained by the Mars Explorer, Mars Pioneer spacecraft, and the Hubble Telescope, as well as other astrophysics-related data. Information shows that liquid water may have existed on Mars in the past. Some aerospace data show that there are structures on Mars similar to the alluvial fans in front of our great floods, as well as water, rivers, rivers like dry riverbeds on Earth, and traces of water erosion of rocks. Another very special point is that at the poles of Mars, conditions similar to the thawing of permafrost on Earth were discovered. This is our aerospace data.

But if we have instruments, bring instruments and people, explore on Mars, or obtain a stone and analyze it, wouldn't these things be clear at a glance? So in early 1999, the United States launched a Mars polar lander, which carried sophisticated analytical instruments and prepared to conduct careful research on the polar regions of Mars. But unfortunately, at the end of 1999, these instruments were expected to get direct information about whether there was water on Mars, but they lost contact with the Earth just as they entered the atmosphere of Mars.