Photos from open sources
When a meteorite crashes into a solid with space velocity the surface of the planet, a powerful thermal explosion occurs, and on it in seconds, a special geological formation – impact meteorite crater. Major clashes this kind could cause massive extinction of species in history Of the earth. However, recent studies suggest that both the occurrence of life could be associated with meteorites craters.
The surface of the globe would look like a real polygon for bombing, pitted with numerous funnels of different sizes, not whether it is protected by a gas shell. Earth collisions with large kilometer diameter celestial bodies occur on average once every a million years. Particles the size of dust particles to a small cobblestone pouring onto our planet almost continuously. Flying into the atmosphere at a speed of tens of kilometers per second, they heat up from friction against the air and burn out before reaching the surface of the Earth. Such is the fate of more than 99% of space debris. Only the largest of them fly to the surface, forming craters that are relatively quickly destroyed by erosion. Therefore, on our planet is not known there are so many meteorite craters – only about 170.
Another thing is the Moon, where there is no atmosphere. Its surface is completely covered with craters across from a few centimeters to hundreds kilometers. The vast majority of them are very ancient. More than 4,5 a billion years ago from dust and rocky debris spinning around the sun, the formation of planets and satellites. Particles gradually stuck together into large lumps, and on the surface of these protoplanets falling ever new fragments. This went on until About 4 billion years ago, a swarm of debris did not run out. Numerous lunar craters are evidence of the last phase called “intense bombardment.”
A photo from open sources
There are almost no craters in the lunar Sea. It turned out that in antiquity lunar craters formed very often, and then beyond short time – from 4 to 3.8 billion years ago – the frequency of falls meteorites decreased a thousand times and since then remains approximately constant. Photo: SPL / EAST NEWS
Space drummers
Meteor, or shock and explosive, craters are the most common landforms on many planets and satellites in The solar system and even on such small objects as asteroids. On the on our planet, the average speed during meteorites is about 20 km / s, and the maximum – about 70 km / s. At the meeting a meteorite with a solid surface, its movement is sharply slowed down, and here are the rocks of the target (that’s the name of the place where it fell), on the contrary, begin accelerated motion under the influence of a shock wave. She diverges in all directions from the point of contact: covers hemispherical region below the surface of the planet, and also moves in the opposite direction on the meteorite itself (drummer). Reaching him back surface, the wave is reflected and runs back. Sprains and compressions at such double run usually completely destroy meteorite.
The shock wave creates tremendous pressure – over 5 million atmospheres. Under its influence, the rocks of the target and the drummer shrinks and heats up. Partially they melt, and in the very center, where the temperature reaches 15,000 ° C, – even evaporate. Solid meteorite debris also falls into this melt. IN the result after cooling and solidification on the bottom of the crater a layer of impactite is formed (from English impact – impact) – mountain rocks with very unusual geochemical properties. In particular, it is very enriched with extremely rare on Earth, but more chemical elements characteristic of meteorites – iridium, osmium, platinum, palladium. These are the so-called siderophile elements, i.e. related to the iron group (in Greek – sideros).
Instant evaporation of a part of the substance leads to an explosion, when where the target rocks are scattered in all directions, and the bottom pressed in. There is a round hollow with pretty steep sides, but it exists for a fraction of a second – then the sides immediately begin to collapse and creep. From above to this mass of soil stone hail falls out of a substance ejected vertically up and now returning to the place, but already in fragmented form. So at the bottom of the crater breccia is formed – a layer of mountain debris rocks cemented with the same material, but crushed to grains of sand and dust.
Collision, rock compression and blast wave passage last tenths of a second. The formation of the excavation of the crater takes order more time. And a few minutes later, shock the melt, hidden under a layer of breccia, begins to harden quickly. AND now ready is a fresh, impassioned heat, impact crater.
In strong collisions, hard rocks behave like liquids. Complex hydrodynamic wave arises in them processes, one of the characteristic traces of which are the central slides in large craters. The process of their formation is similar to the appearance of a drop recoil when a small object falls into the water. Strong impact material ejected from the crater can even fly into space. Exactly So meteorites from the moon and from Mars, tens of which discovered in recent years.
Arizona calculator
The size of the resulting crater depends on the speed and angle of incidence, the composition of the striker and target (stone meteorite or iron, rocky rocks on the planet or loose), as well as by gravity on surface of the celestial body. For example, with the same impact energy a crater of twice the diameter is formed on the Moon than on The earth.
In one of the leading planetary centers of the world – University of Arizona Lunar Planet Laboratory in Tucson developed a special interactive calculator that allows calculate the consequences of a large meteorite falling to Earth or an asteroid (www.lpl.arizona.edu/impacteffects). Among other things, this calculator calculates the size of the resulting crater and impact to observers who are at a given distance from the place disaster. It can be interesting to evaluate what’s reported in news about the possible consequences of the fall of one or another object.
Characteristically, with a small meteorite, the Arizona the calculator refuses to estimate the size of the crater. Small the space chip will either completely burn in the air or lose speed and fall like a simple stone. In the latter case, on surface, of course, a pothole appears, but it is very different from shock and explosive crater, which on Earth can not be less several hundred meters. For other planets, this value depends on atmospheric density. For example, on Venus with its extremely dense with a gas shell, the diameter of the minimum crater is more than a kilometer, and on Mars, they reach the surface almost without loss of speed and small meteorites forming ten-meter-sized craters. On celestial bodies deprived of the atmosphere, for example, on Mercury, the Moon and many other planetary moons, craters are generated by meteorites any size and can even be centimeter.
A photo from open sources
Earth is Manicouagan Crater. Legend of constricted arteries. Photo: SPL / EAST NEWS
Passengers flying from Europe to Canadian Montreal can to notice among the taiga open spaces of the Labrador Peninsula lake. Against the dark background of coniferous forests, a ring of water stands out well, covering from all sides a huge, with a diameter of 70 kilometers, island, also covered with forest. This manicuagan ring structure is one of the oldest among the currently known impact craters, more precisely, his trace. A five-kilometer meteorite fall happened here 214 million years ago. On Earth then ended Triassic period and dinosaurs just appeared. True to it seems that this disaster did not affect them in any way, because the next 150 million years they literally reigned on the planet. Much later a huge glacier crawled along the crater, which cut off the top layer rocks a kilometer thick, but the central part of the bottom the crater resisted glacial erosion because it consists of “cakes” of very hard rocks that arose during melting in moment of impact.
So a plateau was formed, surrounded by a valley along which flowed river. In 1968, the Manicuagan River was blocked by a dam. hydroelectric power stations and it flooded the valleys enveloping a plateau from two parties. A ring lake arose, and the plateau became the island – the second largest in the world among islands in lakes. Its area is 2040 km2 – almost 100 km2 more than the area of Lake Manicoagan itself, in which he is. Rene Levasseur is named after an engineer, who for seven years led the construction of the dam of this hydroelectric station – the fifth and the largest in the cascade on the Manicuagan River. He had to open it Together with Canadian Prime Minister Quebec Daniel Johnson, also a hydropower engineer in the past. But literally on the eve the upcoming opening Levasser suddenly died from heart attack at the age of 35 years. A few days later the same Daniel befell the fate of arriving at the launch ceremony Johnson, who was 53 years old. The island was named in memory of the engineer, the dam – in honor of the prime minister, and in the legends of the Indus Indians, indigenous residents of Labrador taiga, a version appeared that both main the creators of the dam died because nature pressed them blood arteries in revenge for squeezing her water arteries, having built a cascade of hydroelectric power stations on the Manikuagan River.
Dangerous asteroid maneuvers
Large meteorites forming an impact crater on Earth fall extremely rare. However, it is possible that in less than 30 years Earthlings will become witnesses of such an event. Outdoor total five years ago, the asteroid Apophis is small on a cosmic scale. Its exact diameter has not yet been determined, but is estimated to be 300-400 meters. He would not have been disturbed if his path had not ran dangerously close to the Earth. According to astronomers, every 1300 years this asteroid for several decades is not far from our planet, and a series of pretty close encounters at intervals of about 5-10 years, after which the celestial paths of the Earth and the asteroid again diverge for a long time.
In 2029, Apophis will pass at a distance of about 33,000 kilometers from the earth. In this case, the impact of the gravitational field of our planet can change the orbit of Apophis so that at the next meeting, in 2036, it will go even closer and maybe even face The earth.
Calculations based on current, insufficiently accurate data on its movement show that a fall in 2036 may occur in a narrow strip a few tens of kilometers wide, passing from the north of Kazakhstan through Siberia to Magadan, further from Kamchatka across the Pacific Ocean to Nicaragua, northern Colombia and Venezuela and then across the Atlantic Ocean to the West Bank Africa.
In a populated area, a fall will lead to total destruction within a radius of 100 kilometers from the place of impact. There will be a crater with a diameter several kilometers, and a significant amount will be thrown into the stratosphere amount of dust, which will significantly reduce solar heat throughout the earth. In the event of a fall into the ocean, even away from coasts, there will be a strong tsunami that will destroy everything coastal cities.
US Planetary Society, headquartered in California, off the coast of the Pacific, already held in 2008 year competition for the best project of protection against collision with Apophis. is he was timed to coincide with the centenary of the Tunguska event, which remains so far the largest invasion from space that occurred in memory of humanity.
Asteroid Defense Projects include High Speed Impact metal “mass” of one ton mass, a nuclear explosion on surface of an asteroid, painting its surface so as to orbit changed under the influence of solar radiation pressure and “gravity tractor” hanging over an asteroid with working ionic engines of small thrust and gradually shifting it to a new orbit with its gravitational pull.
But for starters, Apophis will most likely be sent a small automatic station that takes a picture of him surface, will study the gravitational field by which one can judge the internal structure of the asteroid, and most importantly – will drop onto it a beacon for accurately tracking its trajectory from Earth. This a relatively inexpensive project by American engineers took first place on the planetary society competition. Only after clarification asteroid motion parameters will be possible to plan correction of its trajectory. After all, the worst thing that can happen is – it hurry up and push the asteroid in the wrong direction directly to our planet.
A photo from open sources
The moon is the crater Tsiolkovsky. Dark eye on the back of the earth satellite. Photo: SPL / EAST NEWS
One of the most picturesque among tens of thousands of lunar craters called Tsiolkovsky. The name of the Kaluga teacher of physics and mathematics, became the founder of the theory of interplanetary communications, appeared on the map of the moon in 1959, when using one of the first “lunar” – the automatic station “Luna-3” – was first photographed the reverse side, never visible from Earth, of our satellite. For this it took to fly around the moon, and then transfer pictures on the radio using approximately the same device, as in modern fax machines – the image is automatically divided into points of different brightness, which lined up a row for string. The pictures taken half a century ago did not differ much clarity, but two dark details stood out very well on them. They are sharply contrasted with the light area, which occupies almost the whole back of the moon. The larger one was called the Sea Moscow, and the smaller one is Tsiolkovsky. This crater diameter 180 kilometers is located in the southern part of the reverse hemisphere of the moon and serves as an excellent reference point on lunar maps and when flying around The moon.
The fact is that inside it is a frozen black lake lava, in the center of which a bright spot stands out as a bright spot, characteristic for large impact craters. On the far side of the moon there are no vast dark plains – lunar seas, because the crust is thicker there than on visible side, and magma was hard to break out of the bowels of the surface. In the Tsiolkovsky region, the thickness of the lunar crust reaches almost a record high – 75 kilometers, so you should think that during the formation of this crater, the impact of the meteorite was especially strong – probably it happened at a very high speed, and the cracks under the crater penetrated extremely deep into the lunar interior, reaching a layer of magma. From there, the basaltic melt poured onto the surface and half flooded the crater bowl, forming after solidification a black plain on which the central slide resembles island with steep banks. As a result, the entire crater acquired the appearance of a dark eye with a bright pupil, and his eyes are already billions years directed to space distances, the study of which with the help of “jet devices” Konstantin Eduardovich Tsiolkovsky reflected in the century before last, creating back in 1896, when he was only 39 years, a mathematically rigorous theory of jet propulsion.
The wealth of “star wounds”
At the end of the XVII century, the English astronomer Edmund Halley expressed the assumption that comets may fall to Earth, causing global catastrophes similar to the biblical Flood. He even believed that a collision of the Caspian arose from such a collision seas – in those days the Caspian was depicted on a map in the form of a circle, resembling a giant crater. However, such ideas did not remain more than assumptions until they began to discover on Earth real evidence of such disasters. Usually these are not hollows of the relief, as on the moon, and the ring structures representing traces of past craters, almost worn from the surface of the Earth active geological activity, primarily water erosion. Geologists called them astroblems, which is translated from Greek means star wounds.
In places where celestial bodies fall on Earth, they often form a variety of mineral deposits. Moreover, deposits in astroblems are unique in scale and mineral composition. So, in the north of Siberia in the Popigai crater with a diameter of 100 kilometers, diamonds formed during the impact of a meteorite in rocks containing graphite. Many astroblems serve as industrial ore sources, for example, about half of the world’s ore nickel associated with Sudbury deposit in Canadian province Ontario. It is believed that the oval in terms of geological structure the size of 60 × 25 kilometers, in which mining is conducted, is formed in the distant past with the fall of a large meteorite. Along with nickel in Sudbury also produces more expensive platinum metals, and also copper, cobalt, selenium, tellurium, gold, silver. These elements were not at all brought to Earth by a meteorite.
A colossal explosion led to the cracking of the bowels into large depth, and from there substances began to flow through the faults, formed the ore field, which is considered one of the richest in the world.
Among the largest and most ancient astroblems, perhaps, is The Central Urals ring structure with a diameter of 550 kilometers. The eastern part of the rampart of this structure is clearly expressed as rather sharp arcuate bend of the middle section of the Ural mountain range, which generally goes almost strictly from north to south. The vast majority of Ural mineral deposits concentrated in this arched, lowest part Ural Mountains, called the Middle Urals. They mined here, and even before iron, copper, chromium, nickel, titanium, uranium are still mined, gold and other metals, deposits are concentrated here gold and famous gems. Deposits are confined to earth faults crust resembling a giant astroblem. These faults and serve as “outlets” for the receipt of ore material from depths of the earth’s interior. The inside of this giant crater gradually filled with sedimentary rocks in which oil fields of the Volga-Kama region.
In addition to form, astroblems stand out as “alien” geological structure in relation to the surrounding area. The rocks uncovered during the formation of the crater differ sharply in age and on the geological map are visible as a kind of blots. The landscapes formed on the places of the former craters also differ – against a background of a homogeneous steppe or taiga, areas with concentric arrangement of the river network, vegetation, soil, which is clearly visible in satellite images. That’s why with the advent of satellites shooting our planet has increased dramatically the number of discovered traces of ancient meteorite falls.
A photo Open Source Martian Car Prototype Testing and spacesuits in a meteorite crater on the Canadian island of Devon (artificial colors). Photo: HAUGHTON-MARS PROJECT / P. LEE
Disaster on the Yucatan
If 65 million years ago, someone could look at the Earth from hand, he would see over the area of the current Mexican the Yucatan Peninsula, a massive explosion thrown into the near-Earth space is a huge mass of matter in the form of a giant funnel. By the opinion of many researchers, then our planet was faced with an asteroid having about 10 kilometers across. IN Earth’s atmosphere, it fell apart into fragments that, falling on the surface of the planet, made terrible destruction. Explosion colossal power burned out all life in the region, caused earthquakes, hurricanes, tsunami waves up to 100 meters high and associated floods. Clouds of dust, smoke, ash and steam enveloped the entire Earth, eclipsing sunlight for several years, passed acid rains. There was a long-term cooling. This caused a massive death of many species of plants and animals. Some scholars believe that similar disasters occurred in the history of the Earth repeatedly.
The picture of this disaster is recreated according to the results of the study. very large, with a diameter of 180 kilometers, a crater located at the northern end of the Yucatan Peninsula. This name is giant crater received from located practically in his the center of a small settlement Chikshulub. Despite so large the size of the crater, it was discovered only 30 years ago. The fact is that it is covered by a thick layer of geological strata, and besides only the southern half of the crater is on land, and the rest of it the part is located on the sea shelf and, in addition to sedimentary rocks, hidden also by the waters of the Gulf of Mexico. Gravimetric survey allowed to get an image of this ring structure, inaccessible to direct observation.
The formation time of this crater corresponds to clayey sediments in which the content of extremely rare iridium on Earth is 15 times above background. This iridium layer just serves as a boundary, marking the end of the Cretaceous geological period, for which the fossilized remains of dinosaurs are typical. In later sediments they are almost never found. Hence the assumption that the extinction of these giants, as well as many more species of fauna Cretaceous, brought about a change in climatic conditions, caused by the fall of a giant meteorite that formed a crater Chikshulub. However, it should be noted that we agree with this point of view not all paleontologists.
A photo from open sources
Mars is the crater of Tikhonravov. Why don’t they fly in? A photo: SPL / EAST NEWS
In the name of the designer of rockets Mikhail Klavdievich Tikhonravov (1900-1974) named one of the largest craters on Mars – diameter its 380 kilometers. It was formed in the earliest period the geological history of the Red Planet, and since then on it the spacious bottom fell several more large meteorites, leaving craters across tens of kilometers. As a result, it was created messy pattern meteorite craters scattered randomly. Their additions to the landscape were made by the Martian atmosphere, which famous for the strongest dust storms lasting several weeks – they sometimes hide from view the entire surface of the planet. Though the winds in the rarefied atmosphere of Mars are weaker than on Earth, they are all the Martians, worn out by millennia of erosion, carry away sand, which is much smaller than typical earth.
Shafts of smaller impact craters, towering above a flat bottom vast Tikhonrav crater, serve as obstacles, with collisions with which the wind loses force. Sand carried by him stays near the craters, where dune fields gradually form dunes. The dark color of these sands is due to the high content in them glandular compounds. Sometimes in combinations of craters and dunes you can see funny drawings, like in this picture, where two located nearby craters of the same size along with their complement “eyebrows” of dark dune fields create a complete impression a surprised face, the outline of which is a shaft of a giant crater.
The man whose name this crater now bears launched his first rocket back in 1933, and subsequently headed in design bureau S.P. Queen is developing a plan for an expedition to Mars. Before that he managed to “put his hand” to the first artificial satellite of the Earth, and to the Gagarin “East”, and to automatic interplanetary stations. Designed by him in 1962 for a manned flight to Mars the heavy interplanetary ship was designated by the acronym TMK, which for some coincidence coincided with the initials constructor. However, the Martian expedition planned at that time for 1974, did not take place, and its prospects are very vague. Can, this is exactly what astonishes the Martian namesake constructor spaceships?
Meteor incubators
Recent studies have shown that perhaps shock craters formed during meteorite falls became those oases where life on our planet arose and began to develop. The US-Canadian science group worked for several years in Hogton meteorite crater on Devon Island in the Canadian Arctic. This crater with a diameter of 24 kilometers is well expressed in the relief. IN conditions of the cold Arctic desert there is almost no vegetation, which facilitates geological exploration. Moreover, the landscape and climatic conditions here are to some extent reminiscent of Martians, and so right inside the crater were lightweight frame houses of an unusual tent were installed, cylindrical shape imitating a base on Mars. Tested here prototypes of spacesuits and vehicles on the surface of Mars – four- and six-wheeled “Marscycles”, on each of which can ride one person. It is in the vicinity of this semi-fantastic settlements and finds were made that allowed a new look on the role of impact craters in the origin and evolution of life.
Canadian Space Agency Geologist Gordon Osinsky, Having carefully analyzed the minerals from the rocks that make up this crater, found that 23 million years ago in an explosion that formed crater, there was a network of deep cracks along which from the bowels to the surface began to flow hot water with dissolved in it salts. After tens of thousands of years, the temperature of these geothermal sources decreased so that they were able to live microorganisms. The crater cavity itself also contributed to the creation of favorable living conditions, protecting from external influences and concentrating solar heat on its slopes. In the crater arose a lake that existed for a long period, and now layers sediments accumulated at its bottom serve as evidence changes that have occurred on our planet in the past. Hydrothermal formations are generally considered favorable places for the development of life, and it is their traces that are found in many impact craters.
On any planet, such craters are the most interesting objects that could potentially hold traces past life. First of all, this refers to Mars, where the search traces of life it is best to keep inside the meteorite craters.
If previously it was believed that their education should only lead to environmental changes that cause massive extinction of species, a new look suggests the opposite: impact craters could be comfortable living habitats organisms, especially in the cold regions of the globe. According to modern ideas, life on Earth arose about 3.8 billion years ago – just at the time when it ended intense meteorite bombing and craters galore covered the surface of a young planet. Perhaps they became cozy “nests”, but rather “aquariums” for the first inhabitants Of the earth.
George Burba
Water Time Dinosaurs Life Moon Mars Islands Rocket Siberia
