Meteorites

A meteor is a bright streak of light in the sky (a "shooting star" or a "falling star") produced by the entry of a small meteoroid into the Earth's atmosphere. If you have a dark clear sky you will probably see a few per hour on an average night; during one of the annual meteor showers you may see as many as 100/hour. Very bright meteors are known as fireballs.

A meteorite is a meteor that survives an impact with the Earth's surface. While it's still out in space it is called a meteoroid. When it enters the atmosphere, impact pressure causes the meteoroid to heat up and emit light, thus forming a metwor or fireball. 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 or not.

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 came through 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 are always named for the place where they were found, usually a nearby town or geographic feature. One notable exception is Barringer Crater (commonly referred to as Meteor Crater) in Arizona which is named after the man who posited that it was formed in an impact with an extraterrestrial object. In cases where many meteorites were found in one place, the name may be followed by a number or letter (e.g., Allan Hills 84001 or Dimmitt (b)). Some meteorites have informal nicknames: the Sylacauga meteorite is sometimes called the "Hodges meteorite" after Ann Hodges, the woman who was struck by it; the Canyon Diablo meteorite, which formed Meteor Crater has dozens of these aliases. However, the single, official name designated by the Meteoritical Society is used by scientists, catalogers, and most collectors.

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 Earth's atmosphere. However, an estimated 500 meteorites ranging in size from marbles to basketballs or larger do reach the surface each year; only 5 or 6 of these are typically recovered and made known to scientists. Few meteorites are large enough to create large impact craters. Instead, they typically arrive at the surface at their terminal velocity and, at most, create a small pit. Even so, falling meteorites have reportedly caused damage to property, livestock and people.

One of the primary goals of studying meteorites is to determine the history and origin of their parent bodies. Several metoerites recovered from Antarctica since 1981 have conclusively been shown to have originated from the moon based on compositional matches of lunar rocks obtained by the Apollo missions of 1969-1972. Sources of other specific metorites remain unproven, although another set of eight meteorites are suspected to have come from Mars. These meteorites contain trapped atmospheric gases which match the composition of the Martian atmosphere as measured by the Viking landers in 1976. All other groups are presumed to have originated on asteroids or comets; the majority of meteorites are believed to be fragments of asteroids.

Solar System Links & Resources

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Meteor & Meteorite Links & Resources

ANSMET: International Meteor Organization The International Meteor Organization (IMO) was founded in 1988 and has more than 250 members now. IMO was created in response to an ever growing need for international cooperation of meteor amateur work. The collection of meteor observations by several methods from all around the world ensures the comprehensive study of meteor showers and their relation to comets and interplanetary dust. ANSMET: The Antarctic Search for Meteorites This page has been designed to give you a pictoral tour of how and why ANSMET hunts for meteorites in the Antarctic. ANSMET is a program supported by grants from the Office of Polar Programs of the U.S. National Science Foundation and by the Solar System Exploration Division of NASA. Meteorites and Their Properties A fantastic primer about meteorites. If you think you've found a meteorite, then you need to read this. Meteors, Meteorites and Impacts Information about meteors, meteorites, fireballs and impacts. Dutch Meteor Society (DMS) DMS is probably most well known for it's photographic results and pioneering work in this particular (and important) subfield of meteor astronomy. At present, DMS is by far the World's largest producer of high precision photographic and videographic orbital elements on a scale which both qualitatively and quantitatively matches and often even surpasses the professional results in the IAU photographic database at Lund (Sweden). DMS photographic results of the last 15 years are at this moment under preparation for publication in a professional journal and for addition to the IAU database at Lund. DMS runs 7 permanent automatic all-sky stations, which are part of the larger European Network (EN). Arizona Meteorites Includes a clickable map of meteorite finds in Arizona along with a list of those finds and pictures of the various meteorites. Collecting MicroMeteorites There is an easy way to collect meteorites, but we must be satisfied with finding small metal ones. They are actually microscopic and are known as micrometeorites. Tons of these fall on Earth each day. Meteorite and Impacts Advisory Committee The Meteorites and Impacts Advisory Committee (MIAC) is a volunteer group of geologists and astronomers which serves as the coordinating body for meteorite and impact reporting and research in Canada. Lunar Meteorites Lunar meteorites, or lunaites, are meteorites from the Moon. In other words, they are rocks found on Earth that were ejected from the Moon by the impact of an asteroidal meteoroid or possibly a comet. A great resource for information about Lunar Meteorites, such as what they are, what to do if you think you've found one, and how we know a meteor is from the Moon rather than somewhere else. Lunar Meteorite List An up-to-date (and subject to frequent change) list of Lunar Meteorites. Mars Meteorites Of the 24, 000 or so meteorites that have been discovered on Earth, only 34 have been identified as originating from the planet Mars. These rare meteorites created a stir throughout the world when NASA announced in August 1996 that evidence of microfossils may be present in one of these Mars meteorites. This site offers news and information about Mars Meteorites. Mars Meteorite Compendium NASA website listing all the Mars Meteorites found so far as well as lots of background information. All About Meteorites French site (English version) that introduces you to the fascinating world of meteorites and the science of meteoritics. In their Basics and FAQ sections they offer beginner to medium content. For experts, the Classification section provides a great survey of each and every class of meteorites, including subgroups and grouplets. Meteorites Australia Meteorites Australia is one of the world's most comprehensive internet sources for meteorite information and photographs. There are many pages including the complete Meteorite Classification List, 'Found A Meteorite' and the Meteorites Australia Collection with many, many others you can also browse through. Meteorite Magazine Meteorite magazine serves as a forum for communication between amateurs, collectors, dealers, educators and researchers interested in meteorites. It is published quarterly in February, May, August, and November. Mars MeteoriteArticles.com Mark Bostick's site provides a wide range of articles about meteorites, meteorite collecting and historical meteorite falls. The Meteorite Times Meteorite-Times Magazine is free, online meteorite magazine with articles on meteorites, tektites, meteorite dealers and people. This online meteorite magazine also has free meteorite classifieds, meteorite dealers, links directory and more. Anomalous Meteor Phenomena Deals with meteors emitting sounds and a range of anomalous meteor phenomena (AMP) recorded by observers throughout the world.

Meteorite eBooks & Articles

Exploring Meteorite Mysteries eBook in PDF format. Left-click to read in your browser or Right-click to download. The study of meteorites provides a unifying theme that links almost every aspect of Earth and planetary science with mathematics, physics, chemistry and even biology. This educator guide provides information and acitivities related to meteorites and their origins, whether it be Mars, asteroids, or the moon.