This time, chang'e-5 took 2 kg of soil and rock samples from the northern part of the storm ocean. If you return to the ground smoothly, scientists will be busy for a while. I don't know how many papers will be published in top journals. Why do you pay so much attention to this sampling? Because there are so many unsolved mysteries about the moon that scientists are scratching their heads. For example, where does the moon come from? The moon is so special. Mercury and Venus have no satellites. Mars captured two of them in the little planet belt. Only the moon is big and round, and the proportion is surprisingly large. So the origin of the moon is a mystery.

Of course, there are many mysteries about the moon. Apollo collected 380 kg of lunar soil and rock samples in total, and the Soviet lunar series probe also brought back about 400 grams of lunar rock and soil. Scientists at Sheffield University in the UK analyzed four separate samples from Apollo, and combined with samples from the Soviet lunar probe, they found a very strange thing - some of the rock specimens belonged to "meteorite lava.". That is, it melts because of the huge energy of meteorite impact, and then it cools down to become a rock. These meteorite lava represents meteorite impacts over and over. After radioisotope analysis, these meteorite lava were generally formed 3.9 billion years ago. The same year, the California tech team of scientists came to a similar conclusion.

It is very difficult to find rocks older than 3.8 billion years on earth. Therefore, 3.8 billion years ago, we had to rely on samples taken from the moon and meteorites falling from space. Caltech's team found that the ages of meteorite impact lava collected from the moon are concentrated in a narrow range of 3.9 billion years ago, up and down less than 50 million years. According to the probability analysis, during this period of time, the moon was hit by meteorites very miserably, and the probability of being hit by meteorites increased greatly. So they called it "the ultimate lunar disaster.". However, the name was later renamed "late heavy bombing period", which can also be translated into "late heavy bombing period", or LHB for short.

However, the analysis of radioactive elements used at that time was relatively rough, so many people still doubt this conclusion. Moreover, some people always suspect that the samples obtained by Apollo missions and the Soviet lunar series probes are too few to represent only 4% of the surface area of the moon. By 2000, scientists had found a new way. That's using lunar meteorites for analysis. When an asteroid hits the surface of the moon, maybe a stone will collapse and fly away. The moon's gravity is very small. It will not take much effort to fly out of the gravitational range of the moon. Instead, it will be captured by the earth and finally fall to the earth to become a meteorite. We don't know what part of the moon meteorites actually come from. It should be more random and more illustrative. After analysis, these meteorites are at least 3.8 billion years old. It shows that 3.8 billion years ago, there were a series of very intensive impact events.

So, why did meteorites fly wildly between 3.8 billion and 4.1 billion years ago? If you don't do it sooner or later, just throw "bricks and tiles" at this time? Scientists used computers to simulate the orbits of large planets and various small celestial bodies at that time. The orbits of planets are not fixed, and they can change. About 3.8 billion years ago, big brother Jupiter and second brother Saturn resonated in orbit. The so-called orbital resonance is that the cycle presents an integer ratio, for example, 1:2. For every revolution of Saturn, Jupiter turns 2. Or the ratio of 2:3, the consequences of this simple integer ratio are very serious. The gravity of these two is not for fun.

All kinds of small objects in the asteroid belt were thrown out by the boss and the second of the solar system. Of course, these two are littering, and there is no specific direction. Occasionally, some of them are not long eyed, and they rush to the earth and the moon. The moon is beaten all over the face, and the earth is no better. According to probability calculation, there will be several craters on the earth larger than China's territory. 40 craters 1000 kilometers in diameter. There are 22000 craters more than 40 kilometers in diameter. In terms of time, every 100 years there will be a major disaster, which is totally impossible.

So far, it seems that the evidence is conclusive, and the computer simulation is also very reliable. It seems that the matter can be settled in the later heavy bombing period. But wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait. It was found that the rain sea on the moon had material thrown into the Chenghai sea next door. Chenghai, Yuhai and Jiuhai are three very large craters on the moon. When a small celestial body smashes out of the Yuhai crater, a lot of splashed gravel particles are thrown into the Chenghai crater next door, and the ejected materials will leave traces. This is not wrong.

This is a bad dish. Does the sample collected from Chenghai area by Apollo mission still count? Is it the local stone in Chenghai or the material splashed from the rain sea next door? It's not clear now. Scientists are now in a stalemate. Therefore, they are looking forward to the arrival of chang'e-5. The location of chang'e-5 sampling is far away from the mid latitude area of Apollo sampling. And this area is much younger than the Apollo sampling area. Whether there is a concentrated "late heavy bombing period" depends on chang'e-5. The scientific significance of chang'e-5 sampling return is just so important.

Why are scientists so interested in the later heavy bombing period? Because there's another big problem involved, which is where the water on earth comes from. As for the source of water on earth, scientists have proposed several directions. First, the solar wind blows a large number of hydrogen ions, which later combine with oxygen to form water. At the top of the earth's atmosphere, 1.5 tons of water can be produced every year. Even after 4.6 billion years, the water produced is only 6.75 billion tons. The storage capacity of the Three Gorges reservoir is 39.3 billion cubic meters, which is almost negligible.

The second possibility is that when the earth was formed, it was brought from the womb. If you have jewelry made of Xiuyan Jade, you can't expect that there is water in it. Xiuyan Jade is a serpentine, which contains a large amount of crystalline water, which can be more than 10%. But no one has seen stones squeeze out so much water because water is integrated into the molecules of each rock. Deep in the earth, there are all these water bearing rocks, and the total amount is amazing. If a small part of it becomes liquid water, it can be quite considerable as geological activity or volcanic eruption reaches the surface. According to scientists, these water quantities can be about half of the total global water. So, where did the other half come from? It is likely that it was brought about when asteroids hit Earth. Which stage of the earth is most likely to hit? Of course, it was the late bombing period.

Where does the asteroid get so much water? In fact, there is no shortage of water in the solar system. But most of the water is far away from the asteroid belt. Why? This involves a so-called "snow line". The closer to the sun, the more light, the higher the temperature. Water is in the form of steam, even decomposed by strong radiation. Only when the temperature is low enough, can the water condense into small ice particles and contaminate the dust. Dust with water gradually condenses, forming big stones, gradually collides and accumulates, and finally becomes big celestial bodies.

So, a comet is just a dirty snowball. There's a lot of water on asteroids, too. The devastating disaster in the later heavy bombing period may have brought us the most important material for the birth of life - water. But scientists have also found problems. There is an isotope of hydrogen called deuterium. By analyzing the ratio of hydrogen to deuterium of water in asteroids or comets, it is found that it is not consistent with that on earth. What the hell is going on? We still need to conduct a more detailed survey of asteroids. It's better to send a detector to find out. Now, more and more scientists realize that the early formation of the solar system was far from as simple as we thought. How much water does an asteroid or comet bring? How much water is there on earth? Before or after the formation of the crust? All these should be considered in an all-round way.

This time, chang'e-5 took 2 kg of soil and rock samples from the northern part of the storm ocean. If you return to the ground smoothly, scientists will be busy for a while. I don't know how many papers will be published in top journals. Why do you pay so much attention to this sampling? Because there are so many unsolved mysteries about the moon that scientists are scratching their heads. For example, where does the moon come from? The moon is so special. Mercury and Venus have no satellites. Mars captured two of them in the little planet belt. Only the moon is big and round, and the proportion is surprisingly large. So the origin of the moon is a mystery.

Of course, there are many mysteries about the moon. Apollo collected 380 kg of lunar soil and rock samples in total, and the Soviet lunar series probe also brought back about 400 grams of lunar rock and soil. Scientists at Sheffield University in the UK analyzed four separate samples from Apollo, and combined with samples from the Soviet lunar probe, they found a very strange thing - some of the rock specimens belonged to "meteorite lava.". That is, it melts because of the huge energy of meteorite impact, and then it cools down to become a rock. These meteorite lava represents meteorite impacts over and over. After radioisotope analysis, these meteorite lava were generally formed 3.9 billion years ago. The same year, the California tech team of scientists came to a similar conclusion.

It is very difficult to find rocks older than 3.8 billion years on earth. Therefore, 3.8 billion years ago, we had to rely on samples taken from the moon and meteorites falling from space. Caltech's team found that the ages of meteorite impact lava collected from the moon are concentrated in a narrow range of 3.9 billion years ago, up and down less than 50 million years. According to the probability analysis, during this period of time, the moon was hit by meteorites very miserably, and the probability of being hit by meteorites increased greatly. So they called it "the ultimate lunar disaster.". However, the name was later renamed "late heavy bombing period", which can also be translated into "late heavy bombing period", or LHB for short.

However, the analysis of radioactive elements used at that time was relatively rough, so many people still doubt this conclusion. Moreover, some people always suspect that the samples obtained by Apollo missions and the Soviet lunar series probes are too few to represent only 4% of the surface area of the moon. By 2000, scientists had found a new way. That's using lunar meteorites for analysis. When an asteroid hits the surface of the moon, maybe a stone will collapse and fly away. The moon's gravity is very small. It will not take much effort to fly out of the gravitational range of the moon. Instead, it will be captured by the earth and finally fall to the earth to become a meteorite. We don't know what part of the moon meteorites actually come from. It should be more random and more illustrative. After analysis, these meteorites are at least 3.8 billion years old. It shows that 3.8 billion years ago, there were a series of very intensive impact events.

So, why did meteorites fly wildly between 3.8 billion and 4.1 billion years ago? If you don't do it sooner or later, just throw "bricks and tiles" at this time? Scientists used computers to simulate the orbits of large planets and various small celestial bodies at that time. The orbits of planets are not fixed, and they can change. About 3.8 billion years ago, big brother Jupiter and second brother Saturn resonated in orbit. The so-called orbital resonance is that the cycle presents an integer ratio, for example, 1:2. For every revolution of Saturn, Jupiter turns 2. Or the ratio of 2:3, the consequences of this simple integer ratio are very serious. The gravity of these two is not for fun.

All kinds of small objects in the asteroid belt were thrown out by the boss and the second of the solar system. Of course, these two are littering, and there is no specific direction. Occasionally, some of them are not long eyed, and they rush to the earth and the moon. The moon is beaten all over the face, and the earth is no better. According to probability calculation, there will be several craters on the earth larger than China's territory. 40 craters 1000 kilometers in diameter. There are 22000 craters more than 40 kilometers in diameter. In terms of time, every 100 years there will be a major disaster, which is totally impossible.

So far, it seems that the evidence is conclusive, and the computer simulation is also very reliable. It seems that the matter can be settled in the later heavy bombing period. But wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait, wait. It was found that the rain sea on the moon had material thrown into the Chenghai sea next door. Chenghai, Yuhai and Jiuhai are three very large craters on the moon. When a small celestial body smashes out of the Yuhai crater, a lot of splashed gravel particles are thrown into the Chenghai crater next door, and the ejected materials will leave traces. This is not wrong.

This is a bad dish. Does the sample collected from Chenghai area by Apollo mission still count? Is it the local stone in Chenghai or the material splashed from the rain sea next door? It's not clear now. Scientists are now in a stalemate. Therefore, they are looking forward to the arrival of chang'e-5. The location of chang'e-5 sampling is far away from the mid latitude area of Apollo sampling. And this area is much younger than the Apollo sampling area. Whether there is a concentrated "late heavy bombing period" depends on chang'e-5. The scientific significance of chang'e-5 sampling return is just so important.

Why are scientists so interested in the later heavy bombing period? Because there's another big problem involved, which is where the water on earth comes from. As for the source of water on earth, scientists have proposed several directions. First, the solar wind blows a large number of hydrogen ions, which later combine with oxygen to form water. At the top of the earth's atmosphere, 1.5 tons of water can be produced every year. Even after 4.6 billion years, the water produced is only 6.75 billion tons. The storage capacity of the Three Gorges reservoir is 39.3 billion cubic meters, which is almost negligible.

The second possibility is that when the earth was formed, it was brought from the womb. If you have jewelry made of Xiuyan Jade, you can't expect that there is water in it. Xiuyan Jade is a serpentine, which contains a large amount of crystalline water, which can be more than 10%. But no one has seen stones squeeze out so much water because water is integrated into the molecules of each rock. Deep in the earth, there are all these water bearing rocks, and the total amount is amazing. If a small part of it becomes liquid water, it can be quite considerable as geological activity or volcanic eruption reaches the surface. According to scientists, these water quantities can be about half of the total global water. So, where did the other half come from? It is likely that it was brought about when asteroids hit Earth. Which stage of the earth is most likely to hit? Of course, it was the late bombing period.

Where does the asteroid get so much water? In fact, there is no shortage of water in the solar system. But most of the water is far away from the asteroid belt. Why? This involves a so-called "snow line". The closer to the sun, the more light, the higher the temperature. Water is in the form of steam, even decomposed by strong radiation. Only when the temperature is low enough, can the water condense into small ice particles and contaminate the dust. Dust with water gradually condenses, forming big stones, gradually collides and accumulates, and finally becomes big celestial bodies.

So, a comet is just a dirty snowball. There's a lot of water on asteroids, too. The devastating disaster in the later heavy bombing period may have brought us the most important material for the birth of life - water. But scientists have also found problems. There is an isotope of hydrogen called deuterium. By analyzing the ratio of hydrogen to deuterium of water in asteroids or comets, it is found that it is not consistent with that on earth. What the hell is going on? We still need to conduct a more detailed survey of asteroids. It's better to send a detector to find out. Now, more and more scientists realize that the early formation of the solar system was far from as simple as we thought. How much water does an asteroid or comet bring? How much water is there on earth? Before or after the formation of the crust? All these should be considered in an all-round way.

In short, to solve these puzzles, we still need space technology. We need more detectors like Rosetta and Falcon 2. Only by vigorously developing deep space exploration technology can we change the situation that astronomy can only see but not touch. Let's hope our own asteroid probe is on the way soon.