The Enlightenment from Disappearing Dinosaurs

First of all, the disappearance of dinosaurs

The history of human beings on the earth is no more than 6.5438+0 million years, and dinosaurs once thrived on the earth for nearly 200 million years. Dinosaur families thrive, water, land and sky are everywhere, and their huge bodies rumble like giant tanks. Carnivorous dinosaurs were quick-thinking, quick-responding, bold and strong, fierce and cruel. Other animals, including our ancestors and mammals, just run around in front and make holes in them. It is such a powerful dinosaur family that suddenly disappeared on our planet 65 million years ago. Completely disappeared, leaving only their bones and petrified big eggs that can no longer hatch. The geological period in which dinosaurs lived before their death was Cretaceous (see Geological-Biological Year). We use "K" to represent the next geological period, and we use "T" to represent it. The transition layer between them is called K-T boundary layer. Typical fossils in the K layer are dinosaurs, conifer pollen and weak primitive mammals. There are no dinosaurs in T-layer fossils, but there are many mammals and flowering plants. Through the study of K-layer and T-layer fossils, it is found that not only dinosaurs disappeared, but also 65%-75% species on the earth disappeared. According to fossil calculations, all land animals weighing more than 25 kilograms survived, and none of them lived to the tertiary. Only a few races of our rodent ancestors survived to the tertiary. The extinction of the whole land species reached 88%, with heavy losses. Marine life is better, but not much better. 50% of species are extinct. 95% of marine phytoplankton, which is the basis of marine biological chain and can carry out photosynthesis, is extinct, the distribution structure of marine food collapses, and larger marine animals die soon. Only deep-sea animals are lucky and have completely entered the tertiary period. Obviously, K-T extinction is a large-scale global disaster. Why do marine plankton, almost invisible to the naked eye, disappear from the earth's biosphere at the same time as giant dinosaurs? Really, as some people think, smart mammals stole the big eggs of stupid dinosaurs? Stealing dinosaur eggs should be the same as pulling out tiger teeth! Moreover, zooplankton have no eggs to steal, and there should obviously be deeper reasons for species extinction.

Table 1- 1

Geological-biological year representative (see PPT)

Two. Iridium anomaly in K-T boundary layer and huge crater

Geologist Alvarez became interested in the thin clay layer with the thickness of 1cm in the K-T boundary layer in gubbio. How long has this centimeter been stored? With this question, he went to his father, the Nobel Prize winner in physics, Alvarez Sr., and his father reminded him that iridium in sedimentary rocks came from cosmic dust particles that often hit the earth. The "annual rainfall" of this cosmic particle rain has remained unchanged for hundreds of thousands of years. The total deposition time can be calculated by measuring the iridium content in the deposited layer. They did a lot of measurements seriously and the results were amazing! The iridium content in the limestone layer above and below the clay layer is at a normal level, that is, about 0.03/ 1 billion, but the iridium content in the clay layer itself actually reaches 3/ 1 billion, which is 100 times of the normal level (see Figure 2- 1).

Figure 2- 1

Iridium content map (see PPT)

The conclusion is that so much iridium can only come from outer space, from the impact of meteorites. Because the content of iridium in the most common chondrite is 50/ 1 billion. The researchers also measured the iridium content in other K-T boundary layers, some of which were even higher. From this iridium anomaly all over the world, it can be roughly estimated that the diameter of this meteorite is about 10 km. According to this, Alvarez and his colleagues published a paper in Science magazine, claiming that a huge asteroid or comet hit the earth 65 million years ago, which triggered a series of global disasters. Dinosaurs and most animals and plants were killed, drowned, burned, frozen to death and starved to death, and the whole biological chain collapsed, and the bodies of victims were permanently solidified on the K-T border rich in iridium. As soon as the news came out, scientists quickly dispatched and launched a lot of new research work, and scientific forums surged. Up to now, more than 20 iridium anomalies 120 in the K-T deposit have been accurately determined, and the abnormal values of other platinum group elements have also proved that they originated from meteorites. In addition, scientists also found a large number of pulse durations in the clay layer at the K-T interface. Scientists believe that the cause of this kind of timing can only be the high pressure generated by the impact, and the instantaneous huge pressure generated by the meteorite hitting the earth's crust at an ultra-high speed of tens of kilometers per second suddenly turns the ordinary timing into an impulsive timing. Glass meteorite (Leigong mill) is also found in the K-T clay layer, which is glass particles re-condensed from vaporized meteorites and rocks during impact. Even more exciting is the discovery of a glass meteorite layer up to half a meter thick on the island of Haiti in the Caribbean. There are a lot of smoke and dust in K-T alluvium all over the world, which scientists believe is the legacy of global fire. Later, a boulder with a diameter of 12 m was found in the 350-meter-thick K-T strata on the southern coast of Cuba. Geologists believe that this deposit was caused by a tsunami, which was caused by a meteorite that hit the ocean. Thick glassy meteorites in Haiti and tsunami sediments in Cuba seem to remind people that meteorites are nearby. Scientists have delineated the location of the search crater in the Caribbean, and it seems that it is just around the corner to catch the culprit. It's a pity that the impact scientists have been looking for it for ten years, but they haven't found it. Sceptics are even more eloquent. At this time, a group of geologists who explored oil for the boss came across this huge crater hidden under the 2000-meter-thick alluvium when they were looking for oil by geophysical methods near the Gulf of Mexico. It's really hard to find a place to get it, and it doesn't take much effort to get it! (See Figure 2-2, Crater Mountain on Yucatan Peninsula)

Figure 2-2

Crater Mountain on Yucatan Peninsula (see PPT)

The width of the circular cave in Hiksulebo Crater in Yucatan Peninsula is at least 65,438+080 km. The age of the Leibo ruins is exactly the same as that of the impact ruins all over the world. Unusual iridium, glassy meteorites and other relics can also be traced back to this crater from all over the world, which links the K-T extinction with the Shiksu in Leibo. This irrefutable evidence shows that the impact of meteorites is the number one killer of extinction.

Third, K-T extinction.

65 million years ago, maybe it was "Black Friday". Before death landed, dinosaurs, big and small, looked up and looked at the bright spots that were getting closer and closer in the sky. This "death star" with a diameter of about 10 km is coming towards the earth at a speed of 20-60 km per second. As soon as it touches the atmosphere, it is dazzling light. Then the whole sky is illuminated, and it only takes a few seconds to break through the atmosphere and crash into the earth's crust. Huge kinetic energy is transformed into heat energy and shock wave like lightning, and some meteorites and earth rocks vaporize instantly. The crater dug by the shock wave was 25 kilometers deep, and everything around it was completely destroyed. The sea water has stirred up a huge water wall as high as 5000 meters and is advancing rapidly around. Strong earthquakes have triggered earthquakes and volcanic eruptions all over the world. The explosion instantly stripped off a part of the atmospheric cover on the earth's surface, and the power of the explosion was equivalent to 65,438+/kloc-0,000,000,000 tons of TNT equivalent. The fireball formed by the explosion circled around the earth, and the whole world became a big oil pan, and all the creatures on the earth were being roasted. The forest burst into flames, half the trees burned to ashes, and a large number of creatures died. The influence of dust and smoke from global fires covered the sky, and the sun could not be seen at all for two or three months, and photosynthesis was blocked for about a year. Within a few months after the impact, a thick layer of dust fell all over the world. It is estimated that about 1kg of the earth's surface sank within one square meter, thus forming the first layer of sediments in Tertiary. Plants and marine plankton living on photosynthesis died in large numbers, and the whole food chain collapsed. After the fire was severe cold, the earth's surface generally cooled by more than 20 degrees, and the remaining life continued to disappear in the long "winter" after the impact. After the big impact, nitrogen and oxygen in the atmosphere combined with steam to generate a large amount of nitric acid, and hundreds of millions of tons of sulfur dioxide released after the impact combined with steam to generate a large amount of sulfuric acid. Acid rain with extremely high concentration lasted for a long time. Acid rain erodes plants, dissolves the shells of marine life and kills them. Acid rain has melted the flesh and bones of terrestrial creatures and turned many places into desert barren land, which is probably the most horrible "baptism" in history.

The big collision produced a powerful shock wave, which spread everywhere, crossed the earth and reached another point (the opposite point), causing terrible earthquakes, volcanic eruptions and a large number of lava eruptions. A lot of volcanic ash and acid gas lasted for a long time. All this is undoubtedly adding fuel to the fire of this disaster earth, and then adding insult to injury, making this miserable world more like a real hell. At that time, dinosaurs and mammals had not evolved to the point of being very clever. The cleverest mammal is not smarter than the cleverest dinosaur. Just because dinosaurs are too big and based on plants, they can only be extinct in this continuous disaster. Our ancestors were small omnivorous mammals, and they ate whatever they caught as long as they could satisfy their hunger. Although it suffered heavy losses in this disaster, after all, a few survivors struggled to survive and the population continued. After the extinction of dinosaurs, mammals quickly evolved and occupied a dominant position until an intelligent creature similar to "human" was developed. Without this meteorite, history would be rewritten. I'm afraid another ugly "man" can tell the biological and geological evolution on the earth today.

Fourth, is there extinction?

This question has a double meaning. Was there a mass extinction of life in the history of the earth? Is there any evidence in geological history? This is one of them. Second, will there be such a mass extinction in the future? What actions will humans take?

From the perspective of geological history, in the period of 540 million years ago, there were 24 confirmed biological extinction events, of which 12 has been proved to be related to cosmic impact. The evidence is iridium anomaly, impact time, glass meteorite, large-scale crater and so on. For example, at the end of Eocene 34 million years ago, 25% of biological species were extinct, and global iridium anomalies, glassy meteorite deposits and giant craters with a diameter of 100 km in Bubijia, Siberia have been confirmed. At the end of Triassic, 2120,000 years ago, 60% of the species became extinct, and hit the giant meteorite crater in Maniga, Quebec, with a diameter of about 100 km. There are also large-diameter craters, such as sudbury Crater in Ontario, with a diameter of 200 kilometers, and Fredford Crater in South Africa with a diameter of 140 kilometers. Fortunately, they all came to the earth early in the origin of life. The primitive ocean is a pot of soup of primitive life. This pot of soup must be mixed by these uninvited guests, and the mixed soup may also make life evolve faster. However, it must be admitted that no evidence has been found that the biggest extinction in history was related to the cosmic impact. This time, nearly 95% of the species disappeared. It occurred in the Permian-Triassic boundary layer 225 million years ago. Only a large number of widely distributed basalts, namely Siberian dark igneous rocks, were found there. Is the meteorite too big to burst the belly of the earth? Meteorites have sunk into the mantle, causing a large number of widespread basalt eruptions. The global fire, smoke, acid rain and persistent "cold winter" have destroyed a large number of imperfect life. The widespread basalt is a memorial? Considering that most of the earth's surface is ocean and the seabed is constantly updated, some craters may never be found. The place where meteorite impact marks can be permanently preserved is on the surface of the moon. Looking up at the moon, there are pockmarked faces and pockmarked faces. Obviously, the earth should be bombarded more violently than the moon. In this century, a stony meteorite with a diameter of about 60 meters landed in Siberia in the Big Bang. 1908 at 7: 00 am on June 30, a huge fireball roared past and the flame appeared in the clear sky. Some people were injured by strong radiation, and the landing site exploded, forming a great basin. /kloc-More than 0/000 square kilometers of forest was razed to the ground, with flaming fire pillars, billowing smoke and scorching heat waves. This is the famous Tunguska meteor explosion. The sound of the explosion was heard over 654.38+100,000 square kilometers, and the dust generated by the explosion reached the stratosphere. The night in Eurasia was as bright as day by the light reflected from the dust in the sky, which lasted for several days. Some people speculate that the nuclear spacecraft of aliens may have exploded in an accident, but its explosive equivalent is indeed equivalent to 2 trillion tons of TNT, which is equivalent to detonating 1000 atomic bombs. If it is two hours late, the landing site will be Moscow, and it will become a Moscow meteorite. In a few seconds, all Muscovites will be evaporated or killed. Some scientists have studied the relationship between the size, quantity, time interval and impact energy of meteorites that hit the earth, and obtained the following results:

Figure 4- 1

The relationship between the size, quantity, time interval and impact energy of meteorites hitting the earth (see PPT)

The impact of the Tunguska meteorite is about once every few hundred years, the meteorite with a diameter of 1 km is about once every 200,000 years, and the impact of the K-T extinction is about once every several hundred million years. Meteorites that can cause global disasters are about 1.7 km in diameter and hundreds of thousands of megatons in energy. Even a 3-5 km meteorite will not completely destroy the earth's ecosystem, and human beings can still survive. However, the impact of a meteorite as big as 10 km is hard to say. Maybe all mankind will be extinct, and there may be a few survivors. Unless there is a way to protect all existing species, it is difficult to predict how biological evolution will proceed.

Some people may say that a disaster that only happens once in hundreds of millions of years is still a long way off! Don't forget that the concept of probability only means that it may happen once in hundreds of millions of years, but it doesn't rule out the possibility of happening in the next century or even next year! For asteroids, we can predict their orbits 20 years ago, but for long-period comets, we only have two years at most, because it is too fast. There is no doubt that the continuous bombardment of Jupiter by comet Shoemaker-Levy 9 is an excellent sobering agent for "sit back and relax".

1993 In September, Carolyn Shoemaker found a dismembered comet in the photo of Jupiter taken by Paloma Observatory in California. This comet was torn into 2 1 pieces by Jupiter's strong gravitational field when it approached Jupiter in July/992. After calculation, scientists predict that comet fragments will hit Jupiter in July 1994. By then, almost all telescopes on the earth will be aimed at Jupiter. The glorious moment has arrived. /kloc-in July of 0/6, the first fragment fell into Jupiter's atmosphere at a speed of nearly 60 kilometers per second, and exploded a few seconds later, with a light beam as high as 3000 kilometers. A succession of blows followed. Two days later, the largest debris created a black hole in Jupiter's stratosphere, enough to put the whole earth in it. The continuous impact made Jupiter black and swollen, leaving 2 1 huge scars. Of course, what you see in the telescope is the most magnificent spectacle in the universe. You appreciate, admire and feel, but if the target of these fragments is the earth, I'm afraid what you see in the telescope is destruction and what you feel is fear.

Figure 4-2

Fragment image of comet Shoemaker-Levi 9 (see PPT)

When scientists painfully felt this threat and launched an investigation, they found that there were more than 2,000 near-earth asteroids. Some scientists joked that the earth is like living in a hornet's nest of asteroids. Even more frightening is the long-period comet. I wonder where it will come from. If you really hit it, the luckiest situation can only give you two years to prepare.

Figure 4-3

The largest known 100 near-earth asteroid (see PPT).

The news that celestial bodies may collide with the earth comes from the University of Arizona. Scientists discovered an asteroid with a diameter of about 1.6km on February 6, 1997, numbered1997xf1,and it was listed as the108th asteroid with potential danger. Scientist Jack Hills pointed out that according to the orbit of this asteroid, it will be closest to the Earth in 2028, and it may pass in the lunar orbit 42,000 kilometers away from the Earth. However, the estimated error is 290,000 kilometers, and it is possible to hit the earth, but the probability is not very high. Seriously, its speed is 27,000 kilometers per hour and its energy equivalent is 32× 10 10 tons of TNT, which is several million times more powerful than the atomic bomb exploded in Hiroshima. Once it hits the earth, the whole earth will be seriously damaged.

China Journal website news: On June 14, 2002, an asteroid visited the Earth. At that time, it was closer to the earth than the moon, but human beings didn't say anything, and it took three days to react. Although this asteroid is only as big as a football field, if it collides with the earth, it will be enough to raze a bustling city to the ground. According to the American Space Daily, astronomers discovered this "earth visitor" on June 17, and they named this asteroid 2002MN. It is estimated that it is 120 meters long, and the shortest distance to the earth is120,000 kilometers, which is almost negligible in astronomical concept. In human records, only one asteroid flew closer to the earth than 2002MN, and that was XMI in 1994. On February 9 of that year, its closest distance from the earth was only 105000 km.

2002MN is a light asteroid. It takes 894.9 days to go around the sun. Once it hits the earth, it will only endanger the region, not the whole world, and it will never be like the impact that the earth suffered 65 million years ago. Now, many scientists blame the extinction of dinosaurs on that prehistoric catastrophe.

A press release issued by the Near-Earth Target Information Center of the British National Space Center said: "If Mn hit the Earth in 2002, the damage it caused would be similar to that of 1908 in Tunguska, Siberia, when 2,000 square kilometers of forest were razed to the ground." At that time, the boulder that hit the earth was 60 meters long and 600 times more powerful than the Hiroshima atomic bomb. According to scientists' speculation, once Mn hits the earth in 2002, it is likely to explode in the atmosphere, producing a huge shock wave. However, it is very unlikely that the earth will be hit by an asteroid or comet, and most visitors to the universe will not be so close to the earth as in 2002MN. Its "closeness" really shocked some scientists. Fortunately, I won't fly so close to the earth in the future. Its next visit to the earth will be in 206 1 year, but it will be much farther away from the earth than in June 14. However, human observation and research on light asteroids are obviously insufficient, and scientists are very worried about this. You know, scientists have found that planets rely on their ability to reflect sunlight, while lightweight asteroids do not reflect strong light, and only when they are very close to the earth will they attract human attention, so their danger cannot be ignored. In addition, astronomical telescopes are mostly concentrated in the northern hemisphere, and the southern hemisphere has become a blind spot for human beings. Once the asteroid flies there, people are unprepared. It is said that if the asteroid enters the collision orbit, it will be too late for humans to launch missiles and intercept them, and it will be too late for emergency evacuation of residents. Southern Network News: 1 February 91day may be a life-and-death day for the earth, because astronomers estimate that an asteroid named "2002 NT7" with a width of two kilometers may collide with the earth on that day, and the impact force is enough to destroy a continent and trigger global climate upheaval. At present, astronomers are closely monitoring the trajectory of asteroids to see if the earth can avoid a bullet. However, scientists also pointed out that because the current calculation is still preliminary, many future observations may show that it is not in the same orbit as the earth. It is reported that NT7 was first discovered by American scientists on July 5th, and it completes its revolution around the sun every 837 days. Yeomans, a scientist from the National Aeronautics and Space Administration, said that NT7 had not been discovered before because its trajectory was much more inclined than that of the Earth, because astronomers started to observe the relevant areas not long ago, and said that people should get used to it. In the future, similar impact threats will appear one after another, but it will be proved to be harmless later. On July 9 this year, the asteroid was first discovered by Lincoln Near-Earth Asteroid Research Program in New Mexico, USA. Scientists say that the Palermo threat degree of an asteroid hitting the Earth is 0.06, which is the first object to show a positive number, making NT7 the most dangerous object found in space so far. Researchers estimate that from childhood,

According to the luminosity calculation of the planet, its width is about two kilometers, and its impact speed on the earth will be 28 kilometers per second, which is powerful enough to blow up a continent and cause great ecological damage, and the global climate will change dramatically.

Figure 4-4

The crater in Arizona, USA, with a width of 1.2km and a depth of 200m, was struck by a meteorite weighing 60,000 tons and a diameter of 30m 50,000 years ago. (see PPT)

However, some scientists say that disaster is not necessarily imminent. Yeomans said: "The threat is very small; Basically, every few million years, a planet of this size is expected to hit the earth when the threat finally disappears. Yeomans said that there are many uncertainties when asteroids hit the Earth. He said: "By February 1, 20 19, the location of NT7 may be 10 million kilometers away from us." He further pointed out that people should get used to discovering more similar asteroids in the future. They seem to be threats, but they may prove irrelevant in the end. However, astronomers also pointed out that because each asteroid has its own orbit, cosmic "traffic accidents" like cross collisions are not common. According to experts' analysis, the probability of an asteroid with a diameter of more than two kilometers hitting the earth only happens once every 500,000 years. The impact of an asteroid with a diameter exceeding 1000 meters only occurs once every1000 years.

Researchers at the Massachusetts Institute of Technology in the United States said that observation data show that at least 1 100 asteroids in the solar system may be close to the Earth, posing a catastrophic threat to the Earth, which is 20% more than the estimated data of 750-900 asteroids. Experts estimate that asteroids larger than one kilometer in diameter are enough to cause global damage to the earth.

In the more than 4 billion years since the birth of the earth, the dangerous "whisperd" has left many scars on the earth. At present, there are more than 100 celestial impact craters discovered by human beings, of which the largest and oldest is the Fulide Fokeng in South Africa, with a diameter of 140 km and a history of197 million years. According to the analysis of scientists, what was hit was a meteorite or asteroid with a diameter of 100 meters.

If it has been determined that the disaster star will hit the earth, how will human society act? Sending a special task force to the disaster star and changing its orbit must be completed several years in advance. If there is only a few months' preparation time when the disaster star is found, we have to launch a nuclear explosive device to blow it off its original orbit. A meteorite with a deflection size of 1km needs a 10,000-ton nuclear bomb, and a meteorite with a deflection size of 10km needs a 100,000-ton nuclear bomb. This will also create new dangers: the target is broken into several large pieces and the orbit is more difficult to control. The solution once and for all is to "smash" it, of course, but smashing a meteorite with a diameter of 7 kilometers requires a nuclear bomb of 10 billion tons. What if it is not completely crushed and produces several large fragments? Human technology is far from mature. Maybe we should really build several super "Noah's Arks" to preserve necessary species, even space immigrants, and reduce the risk of extinction. I hope that the K-T extinction will not happen again before the corresponding technology of human beings matures. Perhaps in the face of this threat, mankind can stop killing each other and increase peace, understanding and international cooperation. After all, we only have one green ark-the earth.