Dragon Adventures Wiki Explore. Worlds and Events. Easter Solstice Halloween Christmas. Valentine's Day Pride Month St. Game Information. Poag, C. Year Published: Chicxulub impact event; computer animations and paper models Alpha, T. View Citation. Year Published: Meteoroids and impact craters On a clear night scores of meteoroids streak across the sky. Spall, Henry. Year Published: Gold in meteorites and in the earth's crust The reported gold contents of meteorites range from 0.
Jones, Robert Sprague View Citation. Year Published: The geologic classification of the meteorites The meteorite classes of Prior and Mason are assigned to three proposed genetic groups on the basis of a combination of compositional, mineralogical, and elemental characteristics: l the calcium-poor, volatile-rich carbonaceous chondrites and achondrites; 2 the calcium-poor, volatile-poor chondrites enstatite, bronzite, hypersthene, and Elston, Donald Parker View Citation.
Filter Total Items: 1. Date published: December 8, Attribution: Astrogeology Science Center. Filter Total Items: 4. List Grid. December 31, October 15, Meteorites are divided into three basic groups: irons , stones , and stony-irons. Practically all meteorites contain a significant amount of extraterrestrial iron and nickel , so the first step in identifying a possible meteorite is the magnet test.
Iron and stony-iron meteorites are rich in iron, and will stick to a powerful magnet so strongly that it can be difficult to separate them! Stone meteorites also, for the most part, have a high iron content and a good magnet will happily adhere to them. Many earth rocks will also attract a magnet, so this is not a definitive test, but it's a good step in the right direction.
Lunar and Martian meteorites, and most achondrites stone meteorites without chondrules contain little or no iron and even a powerful magnet will generally have no effect on them.
However, these meteorite types are so extremely rare that, as a general rule, we discount specimens that will not adhere to a magnet. This remarkable device allows specialists to study the composition of suspected meteorites and other materials in great detail. A small specimen is placed in a chamber and then bombarded by accelerated ions. The results appear on an adjacent computer screen in seconds. Iron is heavy and most meteorites feel much heavier in the hand than an ordinary earth rock should.
A softball-sized iron meteorite will likely weigh five or six pounds, making it seem unnaturally dense. Imagine holding a steel ball bearing as big as a grapefruit and you'll get the idea. When a meteoroid a potential meteorite streaks through our atmosphere, tremendous heat is generated by atmospheric pressure.
The surface of the rock melts and the air around it incandesces. As a result of this brief but intense heating, the surface burns and forms a thin, dark rind called fusion crust. Meteorites literally began to burn up in our atmosphere, so they tend to appear darker than the terrestrial rocks around them.
Desert varnish forms on the surface of some earth rocks, particularly in arid areas, and can easily be mistaken for fusion crust by an untrained eye. True fusion crust does not occur on earth rocks. It is delicate and will weather away over time, but a freshly fallen meteorite will exhibit a rich black crust, much like a charcoal briquette. Chondrite meteorite: A prepared end section of the ordinary chondrite Northwest Africa L, found Tindouf, Algeria, displays a wealth of colorful grain-like chondrules and multiple tiny flakes of extraterrestrial nickel-iron.
The specimen pictured weighs Chondrites are the most abundant meteorite group and take their name from the ancient chondrules they contain.
Regmaglypts , popularly known as thumbprints, are oval depressions-often about the size of a peanut-found on the surface of many meteorites. These indentations look much like the marks a sculptor might make with his fingers on a wet lump of clay, hence their name. Regmaglypts are created as the meteorite's outer layer melts during flight and they are another feature unique to meteorites.
As our typical meteorite burns through the atmosphere, its surface may melt and flow in tiny rivulets known as flow lines. These patterns formed by flow lines can be minute, often thinner than a strand of human hair, and they are one of the most unique and intriguing surface characteristics of meteorites. If it is angular, with sharp edges or points and no smooth sides, then it is probably not a meteorite. It is like that with meteorites. If it is stony not iron and has protuberances, then it is probably not a meteorite.
Any protuberances will break off or ablate away. The surface material ablates away as the meteorite comes through the atmosphere. See next. Meteorites are not burned. If it has a pattern that radiates from the center, then it is not a meteorite. If it has concentric features, then it is not a meteorite. If it has layers, laminations, or any kind of planar or parallel linear features, then it is definitely not a meteorite. If there is no gravity, then there is no way to form layers.
Here is the only exception I know about, and it is a terrestrial weathering effect. If it has veins, particularly ones that stick out or appear to be planar, then it is not a meteorite. Some others have veins of metal. Most of the veins in these photos, however, are fractures that have filled with quartz. Quartz-filled fractures are common in Earth rocks but are not seen in meteorites.
If it has fractures or filled fractures, then it is probably not a meteorite. Ordinary chondrites that have been on or in the Earth a long time, will self fracture as they metal rusts, but they will look rusty and not like the rocks in the photos. See story and photo of the Lake House chondrite, for example. If it is whitish on the outside, then it is not a meteorite.
If there is writing or a picture on it, then it is not a meteorite. If you have or find a rock with writing or pictures, then it is probably not a meteorite.
If there is a face on it, then it is not a meteorite. In those that do, the holes are sparse and small. Vesicles require gas and that the rock was once molten. Most meteorites were never molten. Iron meteorites sometimes have holes, however. If it is glassy and vesicular, then it is not a meteorite.
If it contains lots of amygdules, then it is probably not a meteorite. If it is stony and has big holes in it, then it is not a meteorite. If it contains elongated minerals or clasts, then it is probably not a meteorite.
If it has clasts or minerals grains with square, rectangular, or parallelogram shapes, then it is probably not a meteorite. If it contains round things, the round things are not necessarily chondrules. If it contains obvious quartz, then it is not a meteorite. Try to scratch glass with a sharp edge of the rock. If it makes a deep scratch, it is not a meteorite. If it looks metallic and is shiny on the outside, then it is not a meteorite. If it contains fossils, then it is not a meteorite.
Fossils occur in Earth rocks because there is life on Earth. Thus far, we do not have evidence of life on any of the places where meteorites come from, so if it has fossils, it is an Earth rock. If we ever find a meteorite that contain fossil life forms, that would be a big deal, but the burden of proof would be very heavy. If it is reddish, violet, blue, green, yellow, or orange particularly on the inside, then it is probably not a meteorite.
If it is transparent or translucent, it is not a meteorite. If it does not look like other rocks in the vicinity, then it might be a meteorite, but it is probably not. If you found it on a beach, then it is not a meteorite. Both are rich in iron metal. If a stony meteorite landed in the water and later washed up on a beach it would have lost its fusion crust as a result of abrasion by wave action.
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