Meteorite2 - the"falls" enable us to map the...

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Meteorites It is usual to distinguish between meteorites which are meteoric bodies that have fallen to earth, and their originating meteors . Meteorites themselves are divided in "Falls" and "Finds": Finds: are meteorites that have been simply found in the field with no idea necessarily as to when they arrived or whence they came. Falls: are bodies where the arrival is noted - either visually or by radar tracking - followed by their recovery. This group is very small. Several tens of meteors have been tracked on entry but only a handful have been recovered. The falls are important in that they give information on arrival direction, and thus enable us to say from where in the solar system they might have originated. If they are associated with a comet, or asteroid, for example, they might be expected to be residue from that body. If we can consider a meteorite we find to be an example of the primordial matter of the solar system, then
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Unformatted text preview: the "falls" enable us to map the distribution of this. Most falls so far have mapped back to earth-crossi have mapped back to earth-crossing orbits going back into the asteroid belt, suggesting an asteroidal origin. Types of meteorites There are several different types of meteorite: Stones (52.3% of finds) 0-30% metal, sulphides and silicates, a mixture of textures. Stony-irons (5.4% of finds) 50:50 metal/silicates Irons (42.1%) Have densities of order 7.5 10 3 kg m-3 , usually tough Fe/Ni/Co The stones are either of igneous origin (achondrites) or have never been melted (chondrites). The "chondrites" are named after the "chondrules" which are small glassy or crystalline beads of material which are found embedded in them. Nickel seems ubiquitous, and its presence is a good...
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