To begin with let’s find out what meteorites are. They are the so-called small objects of the Solar system, which fall to the Earth from the interplanetary space, parts of the meteoroids, which do not manage to burn up in the atmosphere. The definition of «meteorite» (a word of Greek origin) means phenomenon produced by the entry of space substances called meteoroids into the Earth’s atmosphere. The word for «meteor» in Belarusian is «Znіchka» (probably from the word «znіkats» — to disappear).
Meteoroids enter the Earth’s atmosphere at a speed of from 11 up to 73 kilometers per second. The path length of meteors in the atmosphere is about 100 miles, most meteoroids burn up in the atmosphere at altitudes above 80 km. Extremely bright meteors are called bolides (fireballs); sometimes they end up crashing into the earth’s surface as meteorites. The mass of the meteors is from one-thousandth of a gram to several grams. On a clear night, you can normally see with the naked eye up to 10 meteors per hour. Several billions of meteoroids (the total mass of about 100 tons) fall to the surface of the Earth during each twenty-four hour period. Most meteoroids are stone decay products of comet nuclei. In interplanetary space meteoroids move in swarms stretched along the comet’s orbit. Entering Earth’s atmosphere they form meteor showers, which occur at the intersection of the Earth and the comet’s orbit.
Meteorites, parts of meteoroids, that do not burn up completely, fall to the earth’s surface. Meteorites keep lying on the surface or penetrate into the soil up to 6.5 meters, forming a bowl-shaped hole. It depends on the final mass and velocity of the meteorite, nature of the soil in the site of a meteorite fall. There are stony meteorites (92% of the total number), stony-iron (2%) and iron meteorites (6%). They consist mainly of aluminum, iron, calcium, and contain no chemical elements that are unknown on the Earth. Typically, they are irregular in shape with the broken edges; more rarely-sharpened at one end and blunt at the other. Usually, meteorites are covered with a thin fusion crust of a thickness not exceeding 1 mm, they are usually black in color (matte or shiny), less frequently-light. Color inside the substance may be light gray, dark gray, black, or almost white.
The mass of a meteorite vary from fractions of a gram to tens of tons; the largest meteorite — the meteorite Goba (Africa), its weight is about 60 tons. Three meteorites per 1 million square kilometers of the earth’s surface fall every year. More than two thousand meteorites got into a global registry. Five meteorites are known in Belarus: «Bragin», «Zhmen», «Gressk», «Zabrodye», «Cherny Bor». Belarusian collection of meteorites is kept at The Institute of Geological Sciences of the National Academy of Sciences of Belarus.
Logoysk Space Alien
The Logoysk crater was discovered by accident. In the mid 70’s geologists conducted planned research, accompanied by the drilling of wells, in 5–7 km to the north-west of Logoysk. The bowels of our land were researched so thoroughly that no one expected any surprises. And suddenly while drilling another well near the village of Kuzevichi geologists revealed just an incredible cut. Rocks, completely unusual for this area and in an unusual sequence, were discovered. Up to 230 meters the thickness of the thin-layered clays and sediments of the lake type was opened under the quarternary, mainly glacial deposits with thickness of 80–160 meters. And then, a layer of unusual and unknown before sedimentary breccias (the so called cemental breccias) was revealed.
A conglomerate is another common type of coarsely fragmented rock, which differs from the breccias by its rounded shape fragments (pebble). They consisted of fragments and boulders, cemented with the same crushed material; in thickness of the breccias, mainly from the bottom; there are lens-like bodies of irregular shape. Their size is up to ten meters and more; here we can find partially or fully molten rocks. In appearance they resemble volcanic lava, more or less littered with debris and small fragments of sedimentary and crystalline rocks. Sometimes melted fragments and the remains of charred wood are found by chance.
Academics went to the place of discovery, made assumptions about what this could be. Geologists followed the volcanic hypothesis and considered that once, in the distant geological past, a volcano could be in that place, after a strong, explosive eruption of which the so-called volcanic caldera formed. And «the boldest hypothesis» was suggested:
This is — a tube explosion, and the above mentioned lava-like rocks are kimberlites, and thus diamonds should be searched there. At that time some leaders of Geological Survey of Belarus unsuccessfully tried to do it.
And such scientists disputes continued the whole ten and a half years. When, in 1976–1977, three more wells were drilled, they gave the opportunity to receive additional material and practically unambiguous arguments in favor of the meteoritic hypothesis. The approximate size of the crater was determined: 15–17 km diameter, not less than 500–600 meters depth, age — about 35–40 million years old. An explosive meteoritic origin of the Logoysk crater became generally accepted.
Extensive works on the territory of the Logoysk crater were held in 1979–1984, during which 30 wells to a depth of 300–500 meters and one — to 1254 meters were drilled, so it was possible to draw, а precise «portrait» of a space alien.
If we went back 25 million years ago, on the place of the Logoysk crater, completely filled and buried under the ancient sediments now, we would see an unusual lake of almost regular round shape,12–15 km in length and 200–500 m in depth, surrounded on all sides by a high solid shaft (100–200 m). It was located on a flat, forested valley, which was then this part of Belarus.
Now this place hardly differs from the rest of Logoyshchina (Logoysk district) with its typical hilly and very picturesque landscape. Only in the northern part of the crater, close to the town Pleshchenitsy, the unusually large for Logoysk hills marsh plain, obliged to the Logoysk crater by its origin, stands out. Now all this peaceful landscape in no way resembles the tremendous catastrophe that happened here about 45 million years ago, which as the annihilation wave swept away all living things for hundreds or, possibly, thousands of kilometers on the European subcontinent.
To imagine, at least roughly, the scale of the devastating environmental consequences of this disaster, we adduce some characteristics. Calculations of scientists show that a stone meteorite moved with a speed of 18 km/s. Its volume was supposed to be about half a billion cubic meters, and the average diameter 650 meters. That was the kind of space «gift», the land of Belarus received in the relatively recent geological past.
A reasonable question arises of how often similar catastrophes took place in the history of the Earth, what the incidence probability of large cosmic bodies on our planet exists and to what extent they threaten present and future civilizations. This question and similar ones can not be answered clearly for many reasons. The main thing is that such incidents are the phenomena of variable probability in time and that there weren’t any catastrophic crashes of large cosmic bodies registered for the whole history time, 3–4 thousand years, that is only a moment in comparison with the geological, and especially astronomical history of the Earth lasting for a few billion years.
Since the beginning of the 20th century, there are about 100 craters on the surface of the Earth, identified as meteoritic, their diameter is from a few tens or hundreds of meters up to 100 km, and their age is from two billion years up to geologically «modern». Besides, it is allocated about 130 structures, which, perhaps, are also meteorite impact craters.
Scientists consider that many thousands of impact craters with a diameter more than 1 km had to be formed for the whole geological period on the surface of the Earth. However, the overwhelming majority of them, especially the most ancient, were completely destroyed or damaged beyond recognition by typical for the Earth’s geological processes — water and air erosion, the emergence of the mountains and buried under more young sediments.
It is also known that in the course of time the number of meteorite falls on the Earth and other planets has decreased as a result of the capture by the planets and their satellites of meteorites and other „space debris“, that kept wandering in the Solar system after its formation.
There is no reason to escalate the horrors of the possible fall of a large unpredictable cosmic body» with disastrous consequences just in our time, and «on our heads». In nature, as well as in the Universe, everything is arranged more logically and reasonably than some science fiction writers imagine.