Until the completion of the mission of Apollo XI with the transfer of the Earth from lunar materials, meteorites were the only samples of extraterrestrial matter that were available in astronomy laboratories for analysis.
Meteorites are solid bodies of the solar system that move in very elliptical orbits around the sun and that often fall to Earth. The study of these astronomical phenomena has been and is of great interest, since it allows obtaining very valuable data about the origin, the solar system, about the formation of the planets and about the probable internal structure of the Earth.
At present, numerous asteroids fall on the earth's surface, most of which are sprayed as they pass through the atmosphere, reaching the Earth's surface in the form of meteoric dust. All the tests carried out by the various laboratories and research centers with meteorites indicate that they originated approximately 4,500 million years ago, that is, long before the oldest rocks of the earth's crust, whose ages never exceed 3,500 million. years.
Minerologically speaking, meteorites are made up of two main fractions: alloys of iron, nickel and silicates. According to the predominance of one or the other of both fractions, the meteorites are divided into three groups:
The sideritos, constituted essentially by an alloy of iron (90%) and nickel (8,5%) and characterized by a high density (7,5%).
The siderolites, formed by an alloy of ferronickel and silicates in equivalent proportions, with a density of around 5%.
Aerolites, constituted predominantly by silicates, with an approximate density of 3.5%, that is, the same as the basic rocks of the earth's crust.
Recently the study of the chemical composition of certain meteorites called carbonaceous, has provided very important data. In fact, said meteorites contain an organic fraction constituted by aromatic and aliphatic hydrocarbons, that is, the essential constituents of terrestrial organisms.
These discoveries allow to affirm that in the solar system to which the Earth belongs, and probably other analogous systems, chemical synthesis phenomena have been produced and produced in which intermediate chemical structures are originated and essential in the genesis of the living beings.
