Tuesday, April 2, 2013
Classification of meteorites
While there are different classifications, one of the most important is the collecting feature of composition and origin of meteorites. In this division we find:
1) Primitive: is the most primitive material in the solar system (they have several billion years) that have remained virtually unchanged since they formed, ie never suffered melting or differentiation processes.
It is thought to have formed by direct condensation of the solar nebula and from them formed the bodies of our solar system. That is, these meteorites are much older than the rocks that make up our planet, so it can give us information about the composition and physical-chemical processes that occurred in the early solar system. Primitive meteorites constitute 86% of the meteorites found.
In general, these are called chondrites meteorites because mostly found in its structure an amalgam of igneous nature glassy spherules are called chondrules. Processes primordial materials heated to melt and create the components of chondrites were varied and were possibly varying with time. On one hand, the sun source newborn was intense magnetic fields, a continuous flow of particles of high energy electromagnetic radiation.
There are different types of chondrites because not all of them have unaltered materials whose components are fully representative of the primordial materials, since most of them suffered some kind of alteration in their parent bodies.
Ordinary chondrites: are the most common chondrites that have come to Earth. In its composition are iron and silicates. They often come from small asteroids are classified by their proportional composition of iron.
Enstatite chondrites: stony meteorites consist mainly of a mineral called enstatite MgSiO3. They are not very abundant, but minerals are fossils from which the Earth formed, since its composition is most similar between meteorites that of our planet. So scientists believe that a combination of these meteorites led by aggregation, the embryos constituent of the Earth. This theory also can deduct their small numbers: only a few blocks would have dispersed from the region of terrestrial planet formation to the main belt and from there, we would arrive in dribs and drabs.
Carbonaceous chondrites: Carbonaceous chondrites are also known as chondrites C, accounting for 5% of chondrites falls. They are characterized by the presence of carbon compounds, including amino acids. Have the highest proportion of volatile compounds, so they are considered to have been formed which farther from the sun one of its main features is the presence of water, or minerals altered by it. Thus, we can deduce that formed beyond the line of ice, but contain a mixture of high temperature mineral ores with other lower temperature. Consequently during the aggregation of materials along these outer regions more refractory minerals ice particles were incorporated in its structure and, timelier, hydrated rare minerals which should give protoplanetary disk. The amount of water present in their structure determines their compositional evolution. The action of this water, hydrating minerals, was decisive altering the composition of these, resulting secondary minerals: clays, oxides, carbonates, ...
Chondrites anomalous: Several tens of chondrites whose composition does not allow sorting in a group. Its origin seems to be marked by different chemical-physical processes that have led to these various compositions, resulting in the belt of asteroids.
2) Differentiated: They are the result of mergers or part of their body’s home. That is, these bodies have undergone several transformations in its original components. They come from different planetary bodies and there are three main types: rocky (or achondrites), metalorrocosos and metal. Its components are the result of metamorphic processes occurring in bodies of thousands of kilometers across. Although they can maintain chemical and isotopic signatures of primitive materials, materials are formed by secondary minerals.
Achondrites: are rocks formed on the surface of their planetary bodies. Major sources of achondrites described to date are, in fact, the Moon, Mars and Vesta. We can distinguish which body these meteorites come through that space exploration has allowed us to study these bodies and their composition in detail.
These rocks from discrete bodies are formed by mineral recrystallized, that is, characteristic of the mineral from which bodies. As its origin is the bark of the bodies, achondrites have a composition marked by several factors: the composition of the planetesimals that led to the bodies from which the place of training, and the size of the marked object eg time in which the materials are subjected to high temperatures differentiation promoting chemical. A large planetary body like the Earth will retain enough energy to remain active for billions of years, but one like the moon will cool in less than half a billion years.
Lunar meteorite Allan Hills 81005, belonging to the group of lunar achondrites
But do not think only the Moon and Mars as a possible origin of these meteorites. For starters there are certain groups of primitive achondrites nature must come from originally chondritic objects but which by its composition and size, had to cross a relatively short phase of magmatic activity. There are also other achondrites that have large asteroids, but given the large number of existing asteroids are impossible to determine their exact time.
Meteorites: They come from large asteroids. They consist of approximately 50% metal and 50% silicate (more sulfides), and are classified according to the variations in this ratio. They come from regions of the inner mantle of bodies that had to be excavated differentiated in large impacts. Meteorites are the most important metalorrocosos palasitas containing olivine lot of green, but may have other colors such as yellow, brown or gold if you have suffered weathering processes on land.
Iron meteorites: kernel derived planetary bodies and detached because of large impacts. These meteorites are made of denser materials that are known and considered to be representative of those that make up the Earth's core.
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