The list of Swedish meteorites is short: nine falls and a handful of finds have been recovered during the last 130 years.
The Mars meteorites make up three of these groups. They are divided into several groups that differ strongly from each other. Small amounts of organic compounds which formed in space without involvement of life are present in these meteorites.Īchondrites are stony meteorites without chondrules. The most primitive of all meteorites are the carbonaceous chondrites. They are believed to represent the materials the Earth formed from. Most stony meteorites contain chondrules and therefore are called chondrites.Ĭhondrites have not been melted since their formation and are composed of almost the same proportion of elements as the Earth. The minerals form millimeter-sized, nearly spherical particles of different internal structure called chondrules. They are mainly composed of olivine and a pyroxene mineral virtually absent in terrestrial rocks. Stony meteorites contain smaller amounts of metallic iron and are less magnetic than the iron meteorites. Stony meteorites: chondrites and achondrites Etching of a polished surface with a mixture of nitric acid in alcohol reveals a structure that is shown only by meteoritic iron and which is difficult to produce artificially. Iron meteorites have high densities and are strongly magnetic. All meteorites unaffected by weathering have a thin and well-defined black fusion crust formed by frictional heating in the atmosphere. Meteorites have characteristic properties which make them easy to identify by a specialist. The lakes Siljan, Orsasjön, Skattungen and Oresjön mark the location of the structure. A Swedish example of a major impact is the 365 million years old circular Siljan structure. A well-known example is an impact in Mexico 65 million years ago that is considered to have caused the extinction of the dinosaurs. Very large meteorites strike the Earth with cosmic velocity (more than 11 km/sec) and are vaporized in a cataclysm that may have global consequences. Shooting stars or meteors are very small meteorites consumed by melting and vaporization in the atmosphere. As an average, five new meteorites from falls are recorded globally each year. Comets may also be a source for meteorites, and some very rare types of meteorites are derived from the planet Mars or from the Moon. The meteorites originate from asteroids which through collision with each other were fragmented and thrown into Earth-crossing orbits. The large majority of them are stones (94 %), the remainder are irons composed of iron-nickel metal and a small number are mixtures of stone and iron (the stony-iron meteorites). Meteorites are extraterrestrial material that fall to Earth.
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