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The Willamette Meteorite, the largest ever to be found in the United States |
"A meteorite is a natural object originating in outer space that survives an impact with the Earth's
surface. While in space it is called a meteoroid. When it enters the atmosphere, air resistance causes the body to heat up and emit
light, thus forming a fireball, also known as a meteor or shooting star. The term bolide refers to either an extraterrestrial body that
collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.
More generally, a meteorite on the surface of any celestial body is a natural object that has come from elsewhere in space. 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. As of mid-2006, there are approximately 1,050 witnessed falls having specimens in the world's collections. In contrast, there are over 31,000 well-documented meteorite 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 meteoroids disintegrate when entering the Earth's atmosphere. However, an estimated 500 meteorites ranging in size from marbles to basketballs or larger do reach the surface each year.
The fireball that occurs as the meteoroid passes through the atmosphere can appear to be very bright, rivaling the sun in intensity, although most are far dimmer and may not even be noticed during daytime. Various colors have been reported, including yellow, green and red. Flashes and bursts of light can occur as the object breaks up. Explosions, detonations, and rumblings are often heard during meteorite falls, which can be caused by sonic booms as well as shock waves resulting from major fragmentation events. These sounds can be heard over wide areas, up to many thousands of square km. Whistling and hissing sounds are also sometimes heard, but are poorly understood. Following passage of the fireball, it is not unusual for a dust trail to linger in the atmosphere for some time.
Chondrites - 86% of the meteorites that fall on Earth. Contain round particles called chondrules composed mostly of silicate minerals that appear to have been melted while they were free-floating objects in space.
Achondrites - 8% of the meteorites that fall on Earth. Most achondrites are also ancient rocks, and are thought to represent crustal material of asteroids.
Iron Meteorites - 5% of the meteorites that fall on Earth. Are iron meteorites with intergrowths of iron-nickel alloys, such as kamacite and taenite.
Stony-iron Meteorites - 1% of the meteorites that fall on Earth. They are a mixture of iron-nickel metal and silicate minerals."
This information found: Wikipedia Encylopedia
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Susan Dietel
Meteorites and Space Rocks For Sale. Meteorite Facts, Information and Identification. Meteorite Hunting, Impacts, Prices, Dealer.
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