What meteorites fall to Earth
The vast majority of stone meteorites (92.3% of stone, 85.7% of the total
Chondrules are found in debris orfine-crystalline matrix, and often the matrix differs from chondrules not so much in composition as in crystal structure. The composition of chondrites is almost identical to the chemical composition of the Sun, with the exception of light gases such as hydrogen and helium.
Therefore, it is believed that chondrites were formed directly from the protoplanetary cloud surrounding the Sun, by condensation of matter and dust accretion with intermediate heating.
Achondrites make up 7.3% of stony meteorites. These are fragments of protoplanetary (and planetary?) Bodies that have undergone melting and differentiation in composition (into metals and silicates).
Iron meteorites are composed of iron-nickelalloy. They account for 5.7% of the falls. Iron-silicate meteorites have an intermediate composition between stony and iron meteorites. They are relatively rare (1.5% falls).
Iron-silicate meteorites have an intermediate composition between stony and iron meteorites. They are relatively rare (1.5% falls).
Achondrites, iron and iron-silicate meteoritesreferred to as differentiated meteorites. They presumably consist of matter that has undergone differentiation in the composition of asteroids or other planetary bodies. Previously, it was believed that all differentiated meteorites were formed as a result of the rupture of one or more large bodies, for example, the planet Phaethon. However, an analysis of the composition of various meteorites showed that they were most likely formed from the debris of many large asteroids.
Hibonite crystals in meteorites, formed when the protoplanetary disk just began to cool, contain helium and neon.
Traces of extraterrestrial organic matter in meteorites
Carboniferous (carbonaceous) meteorites haveone important feature is the presence of a thin vitreous crust, formed, apparently, under the influence of high temperatures. This crust is a good heat insulator, so that minerals that cannot withstand strong heat, such as gypsum, are retained inside the carbonaceous meteorites.
Thus, it became possible when researchingthe chemical nature of such meteorites to find in their composition substances that in modern terrestrial conditions are organic compounds of a biogenic nature.
The presence of such substances does not allow us to unambiguously declare the existence of life outside the Earth, since theoretically, under certain conditions, they could be synthesized abiogenically.
On the other hand, if the substances found in meteorites are not products of life, then they can be products of pre-life - similar to the one that once existed on Earth.
- "Organized Items"
When examining stone meteoritesso-called "organized elements" are found - microscopic (5-50 microns) "unicellular" formations, often having pronounced double walls, pores, thorns, etc.
Today is not undeniablethe fact that these fossils belong to the remains of some form of extraterrestrial life. But, on the other hand, these formations have such a high degree of organization that it is customary to associate it with life. Moreover, such forms have not been found on Earth.
A feature of the "organized elements" is also their abundance: there are about 1800 "organized elements" per 1 g of the material of the carbonaceous meteorite.
What is found in the oldest meteorites
- Water from the origin of the solar system
We are talking about the Sutters Mill meteorite - this is a largea meteorite that exploded over Washington on April 22, 2012 with a yield similar to 4 kilotons of TNT. Fragments of a meteorite with a total mass of about 1 kg were found in California.
The study of the meteorite showed that itbelongs to a previously unknown class of carbonaceous chondrites and was formed at the very beginning of the existence of the solar system. In particular, it was discovered aldhamite - an unstable mineral containing calcium and sulfur and is easily destroyed by the action of water. The consortium for the study of the meteorite consisted of more than 40 scientists.
Its peculiarity is that it contains waterfluid inclusions of nanometer size. It turned out that they contain at least 15% carbon dioxide. The new discovery confirms that calcite crystals in ancient carbonaceous chondrites can indeed contain not only liquid water, but also carbon dioxide.
The discovery confirms the theory thatasteroids, rich in small volatile molecules such as water and carbon dioxide, formed outside Jupiter's orbit before moving to areas closer to the sun. The most likely reason for the transfer of an asteroid into the inner part of the solar system may be the gravitational effects of the gas giant.
- Information about a protoplanet in the early solar system
Last May in a remote Sahara regionfound a meteorite weighing 32 kilograms. It was named Erg-Shesh 002 after the place of the fall. French and Japanese scientists examined the rock and came to the conclusion that this is a fragment of a protoplanet. It is older than the Earth - it is 4.565 billion years old.
Erg-Shesh 002 consists of igneous rocks, suchmeteorites are called achondrites. They are found on Earth very rarely and in 95% of cases they are fragments of Mars or the Moon. Basalt is usually found in achondrites, but not in Erg-Shesh 002. At the same time, andesite, an igneous volcanic rock, was found in its composition. Thus, the Sahara meteorite is one of the rarest.
Additional study of the breed showed thatit took about 100 thousand years to cool and solidify. It looks like such materials were likely common on protoplanets in the early solar system. However, the sample itself is considered a very rare find and no other similar sample has been found on Earth. It is also the oldest magnetic rock ever observed.
- Debris from other asteroids
Between the orbits of Mars and Jupiter is socalled the main asteroid belt - this is a cluster of celestial bodies with a size of 1 km. In total, according to various estimates, these objects are from 1.1 to 1.9 million, there may be several million more smaller bodies. The largest of them is the small planet Zerra, with a diameter of approximately 950 km.
Rotate around asteroids from the main beltsmaller objects, which almost do not differ in their composition and properties: they are believed to be formed after collisions and large asteroids. As a result, some debris of these bodies fall to the Earth.
While studying fragments of the 2008 TC3 meteorite,which fell into Sudan in October 2008, the researchers found that there is at least one more large asteroid inside the solar system. During the analysis of the fallen meteorite, it turned out that it contains magnetite and some other minerals, the analogs of which have not been encountered in such meteorites before.
During the analysis of the fallen body withWith an infrared spectrometer, researchers have discovered a variety of sedimentary rocks, such as phyllosilicates and amphiboles: they appear at relatively high temperatures only with water. However, amphiboles have never been found inside meteorites before, except for the Allende meteorite-chondrite: it fell into Mexico in 1969.
Based on the results of their work, the scientists suggested thatthis unusual structure of a fallen meteorite could have appeared there if 2008 TC3 was part of a much larger asteroid, which is comparable in size to Ceres.
One of the found fragments of asteroid 2008 TC3
- Organic compounds
In the meteorite that fell on the USA two years ago,found extraterrestrial organic compounds and ancient minerals. During his research, it was discovered that it contains rich reserves of extraterrestrial organic compounds. Substances of this kind, in all likelihood, came to the early Earth along with meteorites and, possibly, contributed to the creation of life.
After scientists examined the collected almost12 meteorite fragments, they found out that the space object is a type H4 chondrite - a very rare type of celestial body. Previously, such compounds were not found in such chondrites.
Heck and his colleagues intend to further investigate the following findings. They hope this will help determine how and when the first organic molecules came to Earth.
Why study the oldest meteorites
Meteorites almost always come to Earth from the asteroid belt, which lies between the orbits of Jupiter and Mars.
In fact, meteorites are composed of the same substances thatand the planets of the solar system. Scientists study meteorites primarily in order to study the composition of the Earth, because the earth's crust is so thick that it is impossible to break through it to the deepest layers and look inside.
Meteorites formed 4.5 billion years ago, from which astronomers conclude that the solar system arose at one moment.
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