Meteorites are relatively small bodies of extraterrestrial material (meteoroids) which survive the journey through the Earth's atmosphere (as meteors) to reach the planet's surface.
Known as meteoroids whilst out in space, most of these bodies are created when two or more asteriods collide, although a small proportion are formed from the debris thrown into space by the collision of meteorites with the Moon or Mars or pieces of comets.
When meteoroids enter the Earth's atmosphere, usually at high speed, friction with the air causes them to heat up to very high temperatures and emit light so that they can been seen streaking across the night sky as meteors or "shooting stars".
Huge numbers of meteors enter the Earth's atmosphere every year but most are the size of grains of sand and rapidly burn up in the upper atmosphere. Meteors which reach the planet's surface as meteorites are comparatively rare and it has been estimated that about five hundred meteorites the size of a baseball hit the Earth in a year.
Large meteorites, although rare, strike the Earth with considerable force to leave impact craters. The kind of crater depends on the composition of the meteorite, it degree of fragmentation and the angle of its impact to the surface. Because the impacts of large meteorites are rare on Earth, their craters are weathered away over time unlike on the Moon which has no atmosphere.
The collissions may injure livestock, and even humans, property and large impacts can cause widespread devastation. Because of the speeds (and thus energies) involved even cometary material, largely ice, can cause large explosions in the order of megatons when the meteor breaks up above the Earth's surface - the Tunguska Event of 1908 is thought to have been caused by the disintegration of a cometary meteor near the surface.
|
2003.Sep.28 Burning fragments of a meteorite injure at least 20 people and damage homes in the Kendrapara district in Orissa, eastern India.
1982.Nov.08 Meteorite strikes the house of Wanda and Robert Donahue in Wethersfield, Connecticut - a house less than 1 mile away had been struck ten years previously.
1954.Nov.30 First record of a woman struck by a meteorite - Elizabeth (Liz) Hodges, of Sylacauga, Alabama. The meteorite weighing 8 lbs, struck her at home taking a nap and severely bruised her hip.
1911.Jan.28 Falling meteorite reputedly kills dog near Nakhla in Egypt.
1908.Jan.30 Tunguska Event: Fireball in the sky hits central Siberia with a massive explosion leveling 2,000 sq km of forests and causing shockwave to travel twice round the world. Possibly the impact of a small comet.
1868.Jan.30 Village of Pultusk, Poland, showered by small meteorites.
1860 Falling meteorite kills horse in Ohio, US.
1847 17-kg meteorite plunges into the bedroom of three sleeping children in Braunau, Bohemia.
|
There are periods of particularly heavy meteoric activity such as the Leonids which appear about November 17th each year and follow a 33 year cycle associated with the comet Tempel-Tuttle producing thausands of meteors per hour and the Geminids, associated with the object named 3200 Phaethon which peaked after sunset on Friday, December 13th, 2002.
ASTEROID
Asteroids are rocky bodies which orbit the sun, mostly in a belt between the orbits of Mars and Jupiter.
COMET
Comets are composed of ice, gas and rocks and have very eccentric orbits around the sun with periods of between tens and thausands of years, thier orbits taking them far outside our solar system. When they break up they give rise to some metoeriods.
METEOROID
Meteoroids are small bodies of material in space caused by the collision of two or more asteroids or by the break-up of comets.
METEORS, FIREBALLS or "Shooting Stars"
These are meteoroids which enter the earth's atmosphere and are caused to burn brighly by friction with the air at their high speeds. If they survive the journey to the earth's surface, they are known as meteorites.
METEORITES
Meteorites are meteoroids which have survived the passage through the earth's atmosphere as meteors and have reached the planet's surface.
There is also an ever-increasing number of objects orbiting the Earth which are the "space junk" resulting from our own activities.
Chondrites
Chondrites account for about 79% of terrestrial meteorites. They are composed of mafic minerals with small a small grain size indicating rapid cooling and most contain small spherules called chondrules. These meteorites are typically about 4.6 billion years old and are thought to represent material from the asteroid belt. It is unknown how they formed.
Carbonaceous Chondrites
These account for about 5% of terrestrial meteorites. They contain small amounts of organic materials including amino acids and presolar grains. The isotope ratios of Carbonaceous Chondrites are similar to those of the sun. Carbonaceous chondrites are thought to be the unaltered material of the solar nebula.
Achondrites
These account for about 8% of terrestrial meteorites. Their composition is similar to that of terrestrial mafic igneous rocks and thay are sometimes brecciated. Achondrites are thought to represent the crustal material of larger asteroids.
Iron Meteorites
This group accounts for about 6% of terrestrial meteorites. They are composed of iron with intergrowths of iron-nickel alloys, such as kamacite. Unlike chondrites, the crystals are large, representing slow cooling and crystallization. Iron meteorites are thought to be the core material of one or more planets which broke up subsequently to their formation.
Stony Iron Meteorites
These account for about 2% of terrestrial meteorites. They are composed of a mixture of iron-nickel and silicate minerals and are thought to have originated in the boundary zone above the planetary core regions where Iron meteorites originated.
A small number of meteorites possess unique chemical characteristics relative to other members of the larger groups, such as the Lunar or Martian meteorites.
The continual "rain" of rocky material on the planet Earth has been mostly harmless in historic times, as can be seen from the table of events above or the time-line below, because of the general small size of the metoeors which the earth has encountered over this period. It is fortunate that the one major event of the 20th century, the "Tunguska Event" of January 30th, 1908, which produced an atmospheric explosion estimated as high as 15 megatons occured in a sparsely populated region of the Earth causing little injury to humans or damage to property. Had it occured over a major conurbation, its effects would have been catastrophic.
The impact of large prehistoric meteorites has not always been so benign and many scientists believe that the impact of a large meteorite at the end of the Jurrasic era was responsible for the mass extinction of the dinosaurs and that such events have been responsible for the many earlier mass extinctions found in the geological record since life began. Some scientists even believe that the existence of our Moon is due to the impact of a huge meteorite which dislodged the material it is composed of from what has now become the Gulf of Mexico.
That a meteoritic impact will have a catastrophic effect on the human race and, indeed, all life on the planet in the future is inevitable - it is just a matter of time.
When thinking of meteor craters, the popular imagnation immediately seizes upon the much photographed images of the mile-wide "Meteor Crater" in the desert of Arizona but densely populated Europe is ot without its own examples; the German Reis Kettel ('Basin'), with the town of Nordlington at its centre, is 20 km (16 miles) wide and the Steinheim crater (also in Germany) which is 3.8km (2.4 miles) in diameter with the village of Sontheim at its centre.
| 1492.Nov.07 | | The Thunderstone of Ensisheim, a triangular stone meteorite impacts in a cornfield at Ensisheim, Alsace (then in Germany)
The first record of a meteorite\'s fall in modern times | | | | 1492.Nov.22 | | Emperor Maximillian visits Ensisheim, Alsace, to view the Thunderstone of Ensisheim meteorite
Maximillian decided the landing of the triangular meteorite in his territory was a good omen in his ongoing wars with the French and the Turks | | BAAAGBKY | | 1511 | | Monk alleged to have been killed at Cremona by a meteorite | | | | 1650 | | Monk allegedly killed in Milan by a meteorite | | | | 1674 | | Two Swedish sailors allegedly killed on board their ship by a meteorite | | | | 1698.Nov | | Peak of the 33 year cycle of the Leonid meteor shower associated with the comet Tempel-Tuttle producing thausands of meteors per hour | | BAAAGBKN | | 1799.Nov | | Peak of the 33 year cycle of the Leonid meteor shower associated with the comet Tempel-Tuttle producing thausands of meteors per hour | | BAAAGBKN | | 1847.Jul.14 | | 17-kg meteorite plunges into the bedroom of three sleeping children in Braunau, Bohemia | | | | 1860 | | Falling meteorite kills horse in Ohio, US | | | | 1866.Nov | | Peak of the 33 year cycle of the Leonid meteor shower associated with the comet Tempel-Tuttle producing thausands of meteors per hour | | BAAAGBKN | | 1868.Jan.30 | | Village of Pultusk, Poland, showered by small meteorites | | | | 1871 | | Discovery of Meteor Crater in Arizona, US | | | | 1894 | | Arctic explorer Robert Peary finds the 31-tonne Cape York meteorite in Greenland | | | | 1908.Jun.30 | | Tunguska Event: Fireball in the sky hits central Siberia with a massive explosion of some 10-15 megatonnes leveling 2,000 sq km of forests and causing shockwave to travel twice round the world
Possibly the impact of a small comet | | BAAAGBKO BAAAGBKN | | 1911.Jun.28 | | Falling meteorite kills dog near Nakhla in Egypt | | | | 1916 | | Gaston Ripert reports the discovery of the Chinguetti meteorite | | | | 1920 | | Largest surviving meteorite weighing some 60 tons, named Hoba West, found at Grootfontein in Namibia
| | | | 1932 | | Discovery of Apollo, the first asteroid known whose orbit crossed that of the Earth | | | | 1933.Aug | | Foundation of The Meteoritical Society to promote the study of extraterrestrial materials and their history
| | BAAAGBKN | | 1937 | | Foundation of the American Meteorite Laboratory in Denver, US, by Harvey Nininger
| | | | 1947.Feb.12 | | Sikhote-Alin: the second largest meteroidal event of the 20th century | | | | 1953 | | First publication of Meteoritics (now Meteoritics and Planetary Science) by The Meteoritical Society | | BAAAGBKN | | 1954.Nov.30 | | First record of a woman struck by a meteorite -Elizabeth (Liz) Hodges, of Sylacauga, Alabama
The meteorite weighing 8 lbs, struck her at hoe taking a nap and severely bruised her hip | | | | 1965.Dec.24 | | Largest meteorite known to fall on the UK lands at Barwell, Leicestershire
Breaking up on impact, the pieces recovered indicate a mass of 44 kg | | | | 1966.Nov | | Peak of the 33 year cycle of the Leonid meteor shower associated with the comet Tempel-Tuttle producing thausands of meteors per hour | | BAAAGBKN | | 1969.Apr.25 | | Two meteorite fragments fall on Northern Ireland, 60km apart | | | | 1979 | | Meteor: the first Hollywood film to address the threat of a large Meteoric impact with Earth | | | | 1982.Nov.08 | | Meteorite strikes the house of Wanda and Robert Donahue in Wethersfield, Connecticut - a house less than 1 mile away had been struck ten years previously | | | | 1991.May.05 | | Meteorite weighing 0.767kg lands in the garden of Mr A Pettifor, Glatton, Cambridgeshire | | | | 2000 | | british government announces formation of a task force to monitor near-Earth objects | | | | 2001.Nov | | Peak of the 33 year cycle of the Leonid meteor shower associated with the comet Tempel-Tuttle producing thausands of meteors per hour | | BAAAGBKN | | 2002.Dec.13 | | Peak of the Geminid meteor shower associated with the extraterrestrial object named 3200 Phaethon | | | | 2003.Sep.28 | | Burning fragments of a meteorite injure at least 20 people and damage homes in the Kendrapara district in Orissa, eastern India | | |
|
| | | Links to Other Pages on This Site
|
| |
| | |
|
| | | Links to Other Sites
www.meteorite.fr
www.meteoriticalsociety.org
 en.wikipedia.org
|
| |
| | |
|
| | | Links to Other Pages on this Site
|
| |
| | |
Recommend a Book for this Page
Hits on this page since December 6th| Jan | | |  | | 11 | | Feb | | | | | 8 | | Mar | | | | | 3 | | Apr | | | | | 1 | | May | | | | | | | Jun | | | | | | | Jul | | | | | | | Aug | | | | | | | Sep | | | | | | | Oct | | | | | | | Nov | | | | | | | Dec | | |  | | |
| current year: | | previous year: |
DISCLAIMER: Whilst we endeavour to ensure the content of this site is correct, we cannot undertake that information you find here, is, or will remain accurate and complete. We do not warrant that any information contained on this site is fit for any purpose. If you wish to place reliance on any such information you must check its accuracy by some other means before doing so. If you are in any way connected with any location mentioned on this site or have an interest in any of its contents and have an hour or two a month to spare, we would welcome you as a local moderator - please email the webmaster by CLICKING HERE. Privacy Policy
|
|
