Do you know a Meteorite?
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids.When a meteoroid enters the atmosphere, ram pressure (not friction) causes the body to heat up and emit light, thus forming a fireball, also known as a meteor or shooting/falling star. Meteorites have been found on the Moon and Mars. Meteorites that are recovered after being observed as they transited the atmosphere or impacted the Earth are called falls. All other meteorites are known as finds.
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.
Most meteorites are stony meteorites, classed as chondrites and achondrites. Only 6% of meteorites are iron meteorites or a blend of rock and metal, the stony-iron meteorites. Modern classification of meteorites is complex, the review paper of Krot et al. (2007) summarizes modern meteorite taxonomy. About 86% of the meteorites that fall on Earth are chondrites, which are named for the small, round particles they contain. 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.
About 8% of the meteorites that fall on Earth are achondrites (meaning they do not contain chondrules), some of which are similar to terrestrial mafic igneous rocks. Most achondrites are also ancient rocks, and are thought to represent crustal material of asteroids. One large family of achondrites (the HED meteorites) may have originated on the asteroid 4 Vesta. Others derive from different asteroids. About 5% of meteorites that fall are iron meteorites with intergrowths of iron-nickel alloys, such as kamacite and taenite.
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. Most meteorite falls are recovered on the basis of eye-witness accounts of the fireball or the actual impact of the object on the ground, or both. Therefore, despite the fact that meteorites actually fall with virtually equal probability everywhere on Earth, verified meteorite falls tend to be concentrated in areas with high human population densities such as Europe, Japan, and northern India. A small number of meteorite falls have been observed with automated cameras and recovered following calculation of the impact point.
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.
Most meteorites are stony meteorites, classed as chondrites and achondrites. Only 6% of meteorites are iron meteorites or a blend of rock and metal, the stony-iron meteorites. Modern classification of meteorites is complex, the review paper of Krot et al. (2007) summarizes modern meteorite taxonomy. About 86% of the meteorites that fall on Earth are chondrites, which are named for the small, round particles they contain. 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.
About 8% of the meteorites that fall on Earth are achondrites (meaning they do not contain chondrules), some of which are similar to terrestrial mafic igneous rocks. Most achondrites are also ancient rocks, and are thought to represent crustal material of asteroids. One large family of achondrites (the HED meteorites) may have originated on the asteroid 4 Vesta. Others derive from different asteroids. About 5% of meteorites that fall are iron meteorites with intergrowths of iron-nickel alloys, such as kamacite and taenite.
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. Most meteorite falls are recovered on the basis of eye-witness accounts of the fireball or the actual impact of the object on the ground, or both. Therefore, despite the fact that meteorites actually fall with virtually equal probability everywhere on Earth, verified meteorite falls tend to be concentrated in areas with high human population densities such as Europe, Japan, and northern India. A small number of meteorite falls have been observed with automated cameras and recovered following calculation of the impact point.
