The earth has a history of 4.5 billion years, and its history is shaped by one disaster after another. Asteroid and comet collisions, solar flares, mass extinctions, supernova explosions, cosmic ray bombardments... We have all experienced disasters you can think of. So each of us is a "Survivor", and it is a "miracle" that we can be here.
However, these violent events may also be the reason why there is life on earth.
We tend to regard disaster as a bad thing, but there may be various possibilities after chaos. When we destroy something, we can often create something new. The past history of the earth has always been between survival and destruction. It seems to have been in a delicate balance between "good" disasters and "bad" disasters
In 2021, scientists investigated the mysterious things buried deep in the earth. This is a long hidden evidence of our past history of violence.
At 1800 miles below the earth's surface, our core is surrounded by liquid rock. But inside the liquid rock, there is a region 600 miles high and thousands of miles wide, with great density. They are cupping our core like two hands. One of them is half the size of Australia.
Schematic diagram of earth core
Scientists need to explore this rock more than 1000 miles underground to know what these two rocks are made of.
The scientists took samples. You might think: how do scientists sample at this depth?
In fact, scientists did not go deep into the earth's core for sampling, and current technology can not do this. In fact, it is through volcanic eruptions, such as those in Iceland and Samoa, that some of these rocks are dug out of the mantle.
So for scientists, this is a rare opportunity.
These rocks are very old, with a history of 4.5 billion years, which is as old as the age of the earth. So they tell scientists something about how the internal structure of our planet was formed in the early days of the formation of the earth.
These rocks allow scientists to trace back to a terrible era of cosmic chaos.
4.5 billion years ago, the solar system was still a rather desolate place. We were approaching the end of planet formation, and the earth was still growing.
At that time, you may not recognize the earth. Of course, there was no moon.
The young earth and other young planets revolve around the sun. One of them, a celestial body called Theia by scientists, clashed with our home and had a very spectacular collision with the earth
This is the biggest event in the history of the earth! The Theia event completely reshaped the earth ** The impact would melt the rock and release more than a billion tons of debris.
In this incredible collision, the two planets were actually broken up and merged into one big planet. When the molten earth began to form again, huge pieces of Theia gathered together.
The rocks sampled by the scientists are the same age as that of the great collision event. They may be fragments of TEIA. The huge plate of Theia sank into the core of our planet... It has not been found for billions of years.
The earth was reborn in the destructive collision between the two planets. Although the Theia collision is devastating, some things produced by the collision may lead to the possibility of life.
When the two planets joined, part of Theia's iron core merged with earth's iron core. So this means that the earth has collected a larger core than it has.
This is good news for us, because the earth's core is the source of the magnetic field, which protects us. Liquid metals flowing in the earth's core create the earth's magnetic field - a protective layer against the solar wind.
Each "hiccup" of the sun can produce billions of tons of high-energy protons and electrons, which will peel off our atmosphere. Without an active earth's core and magnetic field, we would just be a barren desert like Mars.
So thanks to the extra iron element of Theia, the outer core of the earth melts very large, so it cools very slowly, keeps melting, and continuously generates a strong shielding magnetic field
The Theia event was absolutely huge. It was not a 100 mile asteroid that hit a large crater in the desert. It was a planetary collision.
The impact also caused a huge ring of debris to spread over the earth, which eventually formed the moon
Therefore, do not think that only Saturn has a ring system, and our earth also has a ring system.
The earth once had a ring system
After the collision, the earth tilted at an incredible angle and rotated at an incredible speed, only a few hours a day.
Due to the existence of the moon, the rotation axis of such a large tilt angle is very stable. If there is no moon and the earth is allowed to move by itself, the earth will experience unpredictable and chaotic swings. So it is the moon that stabilizes the earth and the climate
The gravity of the moon on the ocean produces tides, slowing down the rotation of the earth... Thus creating a world ready for life.
If the intensity of Theia impact were a little higher, the earth might not recover so well; But if the collision is not so strong, its impact may not bring us the changes we now think we need.
So we actually want to thank the moon and its ancestor, Theia, for their collision just right, because they make the earth a planet suitable for life. Without them, the author would not have written this popular science article here.
We are fortunate that most planets will not survive such collisions and gain additional satellites from them. Of course, the huge collision between the earth and Theia is not the only danger to our planet.
[supernovae ignite the solar system]
Supernovae are one of the most destructive things in the universe. The energy they release in one second is equivalent to the energy released by the sun in the whole life.
But instead of destroying us, supernovae started the solar system 4.6 billion years ago.
At that time, the solar system was not even a real solar system. It was the predecessor of the solar system. What we see is a cloud of gas and dust collapsing, forming the sun at the center. Around it, a large, flat disk surrounds it. All planets are formed around them
So what caused them to collapse and form new stars? Scientists think it may be a supernova, which pushed the nebula.
When a supernova explodes, it releases elements and substances into space, as well as a large amount of light and energy, and sends shock waves into space at a speed of 29000 kilometers per second. Shock waves compress matter together until it begins to collapse under its own gravity.
This is how our solar system began. But now it is difficult for scientists to find evidence of the existence of the supernova that ignited the solar system, because the ancient supernova explosion disappeared a long time ago.
It's like the case happened 4.6 billion years ago. Now scientists look at the "crime scene" and ask where the "perpetrators" are?
Scientists are trying to solve this ancient "case". They studied asteroids that fell to the earth in the form of meteorites. Because asteroids were crucial to understanding the early solar system. They freeze everything that existed in the early solar nebula.
4.5 billion years ago, asteroids contained information about the sun and the time before the birth of the solar system. When a massive star ends its life as a supernova, it undergoes what we call nuclear formation.
In fact, we call it explosive nuclear generation. Specifically, the explosion produces new nuclei, new elements, heavier elements. It turns out that the type of elements it produces depends on the exploding star.
Scientists use computer simulations to study which elements form when a star 12 times the mass of the sun explodes. Then they compared the simulation results with the analysis results of elements in asteroids found at the birth of the solar system, and the results matched.
So the remnant of this supernova has always been in our solar system, and perhaps on earth as well. Many rocks on earth are made of silicon, which is produced only when a supernova explodes.
In addition, the core of the earth, that is, the material that supports our life - iron and nickel, similarly, this material only appears in the supernova explosion.
In February, 2021, scientists revealed the truth of supernova explosion. These explosions provided seeds for our solar system and materials for building the earth.
The study examined fragments of huge space rocks blasted from Vesta. The debris later landed on earth. These asteroid debris contained not only one but at least two supernova explosions. Our solar system was conceived and enriched by at least two independent supernova explosions.
Because they provide the ingredients for life. Scientists believe that these two supernovae may have enriched different parts of the infant solar system. One provided material that helped form gas planets outside, while the other supernova injected other elements into the solar system, which formed rocky planets, including the earth**
However, if these two supernovae are too close to the solar nebula, they will only tear up the quasar nebula. If they are too far away, the solar nebula will not get anything good. There is a fine line between the two.
Supernova is both the creator and destroyer of the story. They play two roles. So we are really very, very lucky that the solar system has obtained the ingredients needed to build planets, and the earth is formed in a good position.
[bombing of asteroids and comets]
The future of the earth looks bright, but at that time, the largest bombing in history rushed to the earth. In fact, from the moment the earth was formed, we were attacked.
In 2021, a fireball will cross the night sky of Europe; In 2018, a 1500 ton meteor exploded over the Bering Sea, and its energy was 10 times that of the atomic bomb; In 2013, an asteroid exploded over Russia, injuring more than 1000 people
The earth is hit by many asteroids every day. You can regard them as meteors in the sky. These events are violent and destructive, but these space invaders have also brought what every living planet needs - volatile substances.
Volatile substances are those elements that are very light and easy to move. Usually, they are gases. So oxygen, water, carbon dioxide and all these light elements are important components of life.
These elements are abundant on our planet today, but they did not exist when it was first formed.
By observing other star systems that are forming in space, scientists know that planets are very hot and dry when they form, so this means that almost any volatile matter will evaporate.
The young earth is a dry planet, lacking all the precious volatiles necessary for life. These substances must have been sent to the earth after the formation of the earth.
So how did these volatiles get to earth? We will have to mention Jupiter, the "bully" of the solar system again. As Jupiter moves through the solar system, its gravitational pull pulls all objects, basically accelerating them.
Jupiter's orbit will cause countless asteroids and comets to collide with the inner planets of the solar system, including our earth.
Four billion years ago, a huge asteroid and comet storm hit the earth. Some volatiles from objects tens of miles wide fill the earth's oceans and form the atmosphere
Asteroid bombardment
But the transmission of the universe involves both giving and taking. The impact on the atmosphere may be two-way. There may be a very, very powerful impact that will blow away the atmosphere of a fledgling planet.
The impact of a water rich asteroid will provide water, volatiles and new chemicals to the planet's surface. These substances in turn may help to increase the already existing atmosphere.
So this large-scale impact event is the loss of material on the earth? Or will it increase the amount of material on earth?
Details determine success or failure, such as the size, velocity and composition of the impactor.
A study shows that asteroids between 60 feet and 3300 feet wide contribute more to the atmosphere than they take away.
And the velocity of the impact point is also important. Asteroids orbit the sun. When they fall toward the sun, their speed increases and they accelerate.
This is like throwing a coin into those spiral vortices. As the coin gets closer to the center of the vortex, it will rotate faster and faster.
So, in the same way, the closer the asteroid is to the sun, the stronger the gravity of the sun is, and the faster the asteroid travels.
Therefore, the distance between the planet and the star is an important factor affecting the intensity. Again, we are very lucky that the earth is just the right distance from its main star. So when an impact occurs, the energy will not be too high. It has the right amount and speed, and everything will work normally
So we need these impacts to produce life on the earth. Disasters have created a planet suitable for life.
[ignite the spark of life]
How does life start? In myths and legends, there is a saying that a spark can turn cold inanimate matter into living matter.
In a sense, this is true. On earth, this spark may have arrived 4billion years ago. This period, scientists call it: the Hadean.
The Hadean refers to the period from 4.6 billion years ago to 4billion years ago when the earth was formed. It is named after Hades. Hades - the king of Hades in ancient Greek mythology.
So the earth environment in this period was hell. The atmosphere was hot and thick. There was a lot of water vapor around the high-pressure atmosphere. It was very hot and life could not survive.
But the earliest life on earth can be traced back to the Hadean. This is a terrible place. The rocks have melted and the air is poisonous. However, life was born in this chaos
In june2020, Japanese scientists simulated the conditions of this infernal planet, and then tried to reproduce the spark of life. They used a mixture of carbon dioxide, nitrogen, water and iron to replicate the Stygian environment. A small meteor was launched into the chemical at a speed of 2000 miles per hour, triggering a reaction between basic organic elements to create amino acids.
Scientists call amino acids the cornerstone of life. They are the basic components of proteins. Life needs proteins to exist, so that's why they are so important. Without amino acids, there would be no protein; Without protein, there would be no life as we know it.
This experiment proves that meteorite impact can help form the components of life. But more factors are needed to bring these components together to create life. Just like making a cake, you can put oil, flour, butter and sugar together, but if you don't put them in the oven, you can't make a cake. You'll get something else.
Scientists used to believe that violent asteroid impacts prevented the formation of life. Now, scientists believe that they may be an essential factor
If the asteroid impact is large enough and fast enough, it can directly penetrate the earth's crust, and then it can produce hydrothermal vents. Some scientists believe that it is the cradle of life. They provide a warm and humid environment and bring chemicals deep in the earth's crust... The perfect place for life to begin.
These conditions are bad for us, but it's a wonderful place for those molecules that start to bind and work.
The volcanic hydrothermal vents we see in the ocean today provide us with a small window into the primitive earth. The chemical reactions in these hydrothermal fluids seem to be the right ones to create life.
The earth is lucky again. The impact that may destroy everything is the reason for the birth of life.
[the number one public enemy of life - cosmic ray]
When the earth passed the Hadean, the earth calmed down and life took root. At this time, the earth has to face a lot of deadly cosmic bullets.
The universe is a dangerous place for life. Many things will kill life, including asteroid impacts, black holes, supernovae and so on.
But the number one public enemy is cosmic rays. Cosmic rays are very small, but they travel very fast, close to the speed of light. They can penetrate and destroy our DNA.
Our bodies are full of DNA. If DNA is broken down, it may lead to cancer and death. These cosmic rays are the worst for life. They are terrible. However, cosmic rays may have played a crucial role in the evolution of life.
In 2020, scientists from New York University and Stanford University studied biomolecules with double mirror images, called chiral molecules.
In chemistry, the concept of chirality is that when you have two molecules, two chemical substances, they are physically the same, and they are composed of exactly the same substances. But their structures are different. They are images of each other. Such molecules are called chiral.
Billions of years ago, early life may have both left-handed and right-handed DNA and RNA. But right-handed molecules are mostly used in life selection. The reason may be cosmic rays
When cosmic rays hit the earth's atmosphere, they degrade into smaller subatomic particles called μ Mesons. majority μ Mesons all rotate in one direction, so we have these small μ They are very energetic and rotate in a certain way. When they hit a molecule, they interact with the molecule. They can disturb the molecule and change the molecule.
Some scientists believe that these spins μ Mesons are more likely to interact with right-handed DNA and RNA, causing mutations. So if there are right-handed molecular life and left-handed molecular life on the earth, they are both affected by μ Meson attack. Those who are more attacked have more opportunities to produce beneficial mutations**
Therefore, cosmic rays may give right-handed people an evolutionary advantage. Just like rolling dice, if you want to get two 6S, your left hand can only throw them 10 times, while your right hand can throw them 100 times. Obviously, the right hand is more likely to get two 6S than the left hand.
But dice are not always good for life. 359million years ago, life on earth seemed to have run out of luck. At that time, the earth's oceans were full of marine life. At this time, plants also began to settle in the sea and land.
It is in this environment that the earth has experienced one of the largest expansions in the history of life. Suddenly something killed 97 percent of the vertebrate species. Scientists call this extinction the late Devonian extinction event.
One possible explanation is a supernova. When some dying stars explode, they will emit cosmic rays, which bombard the earth's upper atmosphere and promote the chemical reaction of nitrogen into nitrogen dioxide. The gas itself reacts with the ozone layer and destroys it.
Without the protection of the ozone layer, ultraviolet radiation from the sun bombards the earth. This "radiation rain" lasted for thousands of years... Destroyed the DNA of animals and plants, and many species became extinct.
The late Devonian extinction event mainly affected marine organisms. There used to be fish the size of a school bus in the ocean, but now the main fish are not as big as sardine. Small fish breed quickly, and they can adapt and diversify faster than large species in challenging environments.
Mass extinction has indeed killed many organisms, but it has provided an opportunity for other animals and other life forms. It has also created a chaotic and complex environment and promoted natural selection and evolution.
If the supernova is the culprit of the extinction, scientists believe that the culprit is 65 light-years away. If it gets closer, the luck of life on earth will be exhausted. It seems that the existence of life is always in balance on the blade.
When an exploding star gets a little closer to us... We are all destroyed. So there is a good balance between enough violence and too much violence. And we have been very lucky to dance on that edge for 4.5 billion years
This mass extinction reset life on earth and paved the way for our ancestors, quadrupeds. It can be said that catastrophic events are closely related to human evolution.
[the extinction of dinosaurs made human beings complete]
Dinosaurs were once the overlords on the earth. They occupied the main niche and resources. No creature could shake their position. From birth to extinction (231million years ago -65million years ago), dinosaurs "ruled" the earth for about 170million years.
In this period of earth's history, there are huge plants and insects. If they appeared today, they would be very terrible.
66million years ago, a luminous object appeared in the sky. This huge asteroid hit the Yucatan peninsula of Mexico at that time.
Asteroid collisions that led to the extinction of Dinosaurs
The Everest - sized object hit the ground at 40000 miles per hour. The intensity of light is thousands of times that of sunlight. The impact threw trillions of tons of rock and dust into the air. The rocks were heated when they fell back to the ground, putting the earth in a sea of fire.
The impact also produced smoke that covered the entire sky, and the sun no longer shone brightly on the earth's surface. Plants need sunlight for photosynthesis. Without this important energy source, many species will be extinct. As the source of their food disappeared, the herbivorous dinosaurs starved to death, followed by their predators.
This is a huge destruction to all life on earth. The former overlord disappeared in this event. Their extinction paved the way for the evolution of mammals... And finally produced us.
If there were no asteroid impact, we would not be here. As human beings on this planet, we should all thank this asteroid
Some plants benefit from asteroid impacts. To understand what happened to plants after the impact, Smithsonian scientists studied thousands of fossil tropical plants that died after the impact.
This disaster opened the way for the development of new plant types. It changed the plant kingdom and created a richer and more diverse global ecosystem.
Before the asteroid hit the earth, conifers and ferns dominated the tropical forests of South America. But later, volcanic ash from the impact enriched the soil. Then the rapidly growing flowering plants take their place. It actually provides more opportunities for more abundant plant life, which ultimately benefits us humans.
Because it gives us more food sources, this new world order eventually gave birth to the modern Amazon rainforest, where 10% of the earth's species live.
This incident is indeed a huge destructive event, but it has preserved our entire environment. The world has recovered and we are here.
The earth has experienced disasters again and again since its birth. But after each disaster, a new and vibrant world has emerged. Life thrives in disasters, and these disasters are needed to promote evolution.
So we should definitely expect another mass extinction sometime in the future. Maybe that will be our end. An interesting question is, what will happen to humans on earth?