The aerolites, or stony meteorites, show a diversity of mineral elements including large percentages of silicon and magnesium oxides the most abundant type of aerolite is the chondrite, so called because the metal embedded in it is in the form of grainlike lumps, or chondrules. The siderites, or irons, are composed entirely of metal (chiefly nickel and iron). Three general categories are used to classify meteorites. The lunar and Martian meteorites are thought to have been broken away from the moon and Mars by the impact of large asteroids. One of the Martian meteorites-known as ALH84001-is believed by some scientists to show evidence of there once having been primitive bacterial life on Mars, but most experts disagree with this conclusion. Geochemical analysis has shown that more than 170 known meteorites are of lunar origin and more than 100 are of Martian origin. Some meteorites might be fragments of comets others, small asteroids whose orbital paths crossed that of the earth. The age of meteorites can be determined by measuring their radium and helium contents. Since then many studies have been made of their composition and crystalline structure the use of microchemical analysis, X rays, and the mass spectrograph has facilitated such work. did scientists fully accept the fact that meteorites came to the earth from outer space. Because of the destructive effects of this friction, only the very largest meteors become meteorites. Meteorite, meteor that survives the intense heat of atmospheric friction and reaches the earth's surface.
0 Comments
Leave a Reply. |