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More generally, a meteorite on a celestial body is an object that has come from elsewhere in space. The only known examples of meteorites that didn't fall on Earth are Heat Shield Rock , which was found on Mars , and two tiny fragments of asteroids that were found among the samples collected on the Moon by Apollo 12 (1969) and Apollo 15 (1971) astronauts {Link without Title} . Meteorites have traditionally been divided into three broad categories: stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites are largely composed of metallic iron-nickel; and, stony-iron meteorites contain large amounts of both metallic and rocky material. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition and mineralogy. See Meteorites Classification . OVERVIEW in '')]] Most meteoroids disintegrate when entering the Earth's atmosphere, making Impact Event s (Earth impacts) on the surface uncommon. About 500 meteorites ranging in size from peas to basketballs reach the surface each year, although some can be much larger. Large meteorites may strike the ground with considerable force, leaving behind an Impact Crater . The kind of crater will depend on the size, composition, degree of fragmentation, and incoming angle of the meteor. The force of collision may cause widespread destruction. Occasional damage to property, livestock, and even people has been recorded in historic times. In the case of Comet fragments, which are largely composed of Ice , a considerable concussion may occur, even though no fragment of the original meteoroid survives; the famed Tunguska Event is thought to have resulted from such an incident. About 86% of the meteorites that fall on Earth are Chondrite s, which are named for the small, round particles they contain. These particles, or Chondrule s, are composed mostly of silicate minerals that appear to have been melted while they were free-floating objects in space. Chondrites also contain small amounts of organic matter, including Amino Acid s, and Presolar Grains . Chondrites are typically about 4.55 billion years old and are thought to represent material from the Asteroid Belt that never formed into large bodies. Like Comet s, chondritic asteroids are some of the oldest and most primitive materials in the solar system. Chondrites are often considered to be "the building blocks of the planets." , New York .]] About 8% of the meteorites that fall on Earth are Achondrite s, some of which appear to be similar to terrestrial mafic Igneous Rock s. Most achondrites are also ancient rocks, and are thought to represent crustal material of asteroids. One large family of achondrites may have originated on the asteroid 4 Vesta . Others derive from different asteroids. Two small groups of achondrites are special, as they are younger and do not appear to come from the asteroid belt. One of these groups comes from the Moon, and includes rocks similar to those brought back to Earth by Apollo and Luna programs. The other group is almost certainly from Mars and are the only materials from other planets ever recovered by man. About 5% of meteorites that fall are Iron meteorites with intergrowths of iron- Nickel Alloy s, such as Kamacite and Taenite . Most iron meteorites are thought to come from the core of a number of asteroids that were once molten. As on Earth, the denser metal separated from silicate material and sank toward the center of the asteroid, forming a core. After the asteroid solidified, it broke up in a collision with another asteroid. Stony-iron meteorites constitute the remaining 1%. They are a mixture of iron-nickel metal and Silicate minerals. One group, called Pallasite s, are thought to have originated in the boundary zone above the core regions where iron meteorites originated. The other major group of stony-iron meteorites are called Mesosiderite s. Note: Tektites (from Greek ''tektos'', molten), natural glass objects up to a few centimeters in size, were formed--according to most scientists--by the impact of large meteorites on Earth's surface, although a few researchers have favored an origin from the Moon as volcanic ejecta. Tektites are NOT meteorites. METEORITES IN HISTORY One Theory suggests that a large meteorite impact caused the Mass Extinction of the Dinosaur s. It is also theorized that meteorites caused other Mass Extinction Events throughout the History Of The Earth . , the largest ever to be found in the United States ]] The only reported fatality from meteorite impacts is an Egyptian dog who was killed in 1911 , although this report is disputed. The meteorites that struck this area were identified in the 1980s as Martian in origin. The first known modern case of a in her living room after it bounced off her Radio . She was badly bruised. Several persons have since claimed {Link without Title} to have been struck by 'meteorites' but no verifiable meteorites have resulted. Indigenous peoples often prized iron-nickel meteorites as an easy, if limited, source of iron metal. For example, the Inuit used chips of the Cape York Meteorite to form cutting edges for tools. NOTABLE METEORITES
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