NationMaster - Encyclopedia: Meteorite impact

Artist's impression of a major impact event. The collision between Earth and an asteroid a few kilometers in diameter may release as much energy as several million nuclear bombs detonating.

Impact events are caused by the collision of large meteoroids, asteroids or comets (generically: bolides) with Earth and may sometimes be followed by mass extinctions of life. For discussion of impacts in general, not just on Earth, see impact crater. Illustration of an impact event. ... Illustration of an impact event. ... Physical collision Dynamics Deflection happens when an object hits a plane surface In physics, collision means the action of bodies striking or coming together (touching). ... A meteoroid is a relatively small (sand- to boulder-sized) fragment of debris in the Solar System. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) Comet (disambiguation). ... The term bolide (from the Greek βολις, bolis, missile) can refer 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. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... This article is about impact craters. ...

Contents

1 The geology of Earth-impact events

2 Mass extinctions and impacts

3 Recent pre-historic impact events

4 Modern impact events

5 End of civilization

The geology of Earth-impact events

In the past, the Western view of history held that the Earth was created a few thousand years ago, and had been shaped since that time by a number of global cataclysms (see catastrophism). In the course of the first half of the 19th century, the new sciences of geology and paleontology supplanted this view, which gradually gave way to a consensus that the Earth was ancient and that its features reflected gradual changes operating over very long periods of time—a view known as uniformitarianism. Catastrophism is the theory that Earth has been affected by sudden, short-lived, violent events that were sometimes worldwide in scope. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Within scientific philosophy, uniformitarianism is the principle in which one assumes that the same processes that shaped the Universe occurred then as they do now, unless there is good evidence otherwise. ...

This view has been amended in recent decades to accommodate the fact that the Earth has in fact also gone through periods of abrupt and catastrophic change, some due to the impact of large asteroids and comets on the planet. A few of these impacts may have caused massive climate change and the extinction of large numbers of plant and animal species. The creation of the Moon is widely attributed to a huge impact early in Earth's history. Impact events even earlier in Earth's history have been credited with creative as well as destructive events; it has been proposed that the water in the Earth's oceans was delivered by impacting comets, and some have suggested that the origins of life may have been influenced by impacting objects bringing organic chemicals to the Earth's surface. In biology and ecology, extinction is the ceasing of existence of a species or group of species. ... In biology, a species is a kind of organism. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Big Splash illustration The Big Splash The giant impact theory (or Big Splash or Big Whack; cf. ... Ocean (Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ... This article focuses on modern scientific research on the origin of life. ...

These modified views of the Earth's history did not emerge until relatively recently, chiefly due to a lack of direct observations and the difficulty in recognising the signs of an Earth impact. Large-scale terrestrial impacts of the sort that produced the Barringer Crater in Arizona are rare. Instead, it was widely thought that cratering was the result of volcanism: the Barringer Crater, for example, was ascribed to a prehistoric volcanic explosion (not an unreasonable hypothesis, given that the volcanic San Francisco Mountains stand only 30 miles to the west). Similarly, the craters on the surface of the Moon were ascribed to volcanism. The collision of the comet Shoemaker-Levy 9 with Jupiter in 1994 was the first time a major impact event had been directly observed; to date, no such events have been observed on Earth. For the crater on the Moon, see the Lunar Barringer crater The Barringer Crater, also known as the Meteor Crater, is a famous impact crater created by a meteorite, located about 55 kilometers east of Flagstaff in the northern Arizona desert (USA). ... State nickname: The Grand Canyon State, The Copper State Other U.S. States Capital Phoenix Largest city Phoenix [[List of Governors of {{{Name}}}|Governor]] Janet Napolitano Official languages English Only State Area 295,254 km² (6th) - Land 294,312 km² - Water 942 km² (0. ... This article is about volcanoes in geology. ... Categories: Mountain ranges of North America | Arizona mountains | US geography stubs ... Hubble Space Telescope image taken on May 17, 1994. ... Jupiter may refer to: Jupiter (god) – a Roman god Jupiter (planet) – a planet Jupiter Symphony – a symphony by Mozart, (Symphony No. ... 1994 was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ...

It was not until 1903-1905 that the Barringer Crater was correctly identified as being an impact crater, and it was not until as recently as 1963 that research by Eugene Merle Shoemaker conclusively proved this hypothesis. The findings of late 20th century space exploration and the work of scientists such as Shoemaker demonstrated that impact cratering was by far the most widespread geological process at work on the Solar System's solid bodies. As literally every surveyed solid body in the Solar System was found to be cratered, there was no reason to believe that the Earth had somehow escaped bombardment from space. 1903 has the latest occurring solstices and equinoxes for 400 years, because the Gregorian calendar hasnt had a leap year for seven years or a century leap year since 1600. ... 1905 was a common year starting on Sunday (see link for calendar). ... Events January-February January 11 - The Whisky A Go-Go night club in Los Angeles, the first disco in the USA, is opened. ... Eugene Shoemaker at a stereoscopic microscope used for asteroid discovery Eugene Merle Shoemaker (or Gene Shoemaker) (April 28, 1928 – July 18, 1997) was one of the founders of the fields of planetary science and is best known for co-discovering the Comet Shoemaker-Levy 9 with his wife Carolyn Shoemaker... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Space exploration is the physical exploration of outer-Earth objects and generally anything that involves the technologies, science, and politics regarding space endeavors. ...

Based on crater formation rates determined from the Earth's closest celestial partner, the Moon, astrogeologists have determined that during the last 600 million years, the Earth has been struck by 60 objects of a diameter of five kilometers or more. The smallest of these impactors would release the equivalent of 10 million megatons of TNT and leave a crater 95 kilometers across. For comparison, the largest nuclear weapon ever detonated, the Tsar Bomba, had a yield of 50 megatons. This article is about impact craters. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Astrogeology is the scientific discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... Trinitrotoluene (TNT) is a pale yellow crystalline aromatic hydrocarbon compound that melts at 354 K (178 °F). ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... Tsar Bomba (Russian: Царь-бомба) was the largest nuclear explosive device in history. ...

Mass extinctions and impacts

In the past 600 million years there have been five major mass extinctions that on average extinguished half of all species. The largest mass extinction to have affected life on Earth was the Permian-Triassic one that ended the Permian period 250 million years ago and killed off 90% of all species. The last such mass extinction led to the demise of the dinosaurs and has been found to have coincided with a large asteroid impact; this is the Cretaceous-Tertiary (K-T) extinction event. There is no solid evidence of impacts leading to the four other major mass extinctions, though many scientists assume that they are at least related to impacts. An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... In biology, a species is a kind of organism. ... The Permian-Triassic extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 252 million years ago (mya), forming the boundary of the Permian and Triassic geologic periods. ... The Permian is a geologic period that extends from about 280 to 248 million years before the present (mya). ... Orders Saurischia Sauropodomorpha Theropoda Ornithischia Dinosaurs are reptiles that dominated the terrestrial ecosystem for most of their 165-million year existence. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... The Cretaceous-Tertiary (KT) extinction event, also known as the KT boundary (from German: Kreide-Tertiär-Grenzschicht), was a period of massive extinction of species, about 65. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ...

In 1980 Luis Alvarez and his son Walter led a team from the University of California, Berkeley that discovered unusually high concentrations of iridium, an element that is rare in the Earth's crust but relatively abundant in many meteorites. From the amount and distribution of iridium present in the 65 million year old "iridium layer", the Alvarez team later estimated that an asteroid of 10-14 kilometers must have collided with the earth. This iridium layer at the K-T boundary has been found worldwide at 100 different sites. Multidirectionally shocked quartz (coesite), which is only known to form as the result of large impacts or atomic bomb explosions, has also been found in the same layer at more than 30 sites. Soot and ash at levels tens of thousands times normal levels were found with the above. Luis Walter Alvarez (June 13, 1911 – September 1, 1988) of San Francisco, California, USA, was a famed physicist who worked at the University of California, Berkeley. ... Walter Alvarez (born 1940), son of Nobel Prize winner Luis Alvarez, is a professor in the geology and geophysics department at the University of California, Berkeley. ... University of California, Berkeley The University of California, Berkeley (also known as Cal, UC Berkeley, UCB, or simply Berkeley) is a public coeducational university situated in the foothills of Berkeley, California, USA to the east of San Francisco Bay, overlooking the Golden Gate. ... Alternate meaning: Iridium (satellite) General Name, Symbol, Number Iridium, Ir, 77 Chemical series transition metals Group, Period, Block 9, 6, d Density, Hardness 22650 kg/m3, 6. ... Worlds second largest Meteorite in Culiacan, Mexico A meteorite is a relatively small extra-terrestrial body that reaches the Earths surface. ... Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... Soot, also called lampblack or carbon black, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the lack of sufficient oxygen. ... Ash is: The solid residue left after something has burned, usually wood and plant material (such as tobacco). ...

Anomalies in chromium isotopic ratios found within the K-T boundary layer strongly support the impact theory. Chromium isotopic ratios are homogeneous within the earth, therefore this isotopic anomalies exclude a volcanic origin which was also proposed as a cause for the iridium enrichment. Furthermore the chromium isotopic ratios determined in the K-T boundary are similar to the chromium isotopic ratios found in carbonaceous chondrites. Thus a probable candidate for the impactor is a carbonaceous asteroid but also a comet is possible because comets are assumed to consist of material similar to carbonaceous chondrites. Some carbonaceous chondrites. ...

Probably the most convincing evidence for a worldwide catastrophe was the discovery of the crater which has since been named Chicxulub Crater. This so-called smoking gun is centered on the Yucatan Peninsula of Mexico and was discovered by Tony Camargo and Glen Pentfield while working as geophysicists for the Mexican oil company PEMEX. What they reported as a circular feature later turned out to be a crater estimated to be 180 kilometers in diameter. Other researchers would later find that the end-Cretaceous extinction event that wiped out the dinosaurs had lasted for thousands of years instead of millions of years as had previously been thought. This would be the final piece of evidence that convinced the vast majority of scientists that this extinction resulted from a point event that is most probably an extra-terrestrial impact and not from increased volcanism and climate change (which would spread its main effect over a much longer time period). Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater is an ancient impact crater buried underneath the Yucatan peninsula, with its center located approximately underneath the town of Chicxulub, Yucat n, Mexico. ... The Yucatán Peninsula separates the Caribbean Sea from the Gulf of Mexico. ... The United Mexican States or Mexico (Spanish: Estados Unidos Mexicanos or México; regarding the use of the variant spelling Méjico, see section The name below) is a country located in North America, bordered to the north by the United States of America, to the southeast by Guatemala and Belize, to... Geophysics, the study of the earth by quantitative physical methods, especially by seismic reflection and refraction, gravity, magnetic, electrical, electromagnetic, and radioactivity methods. ... Oil is a generic term for organic liquids that are not miscible with water. ... Petróleos Mexicanos (Pemex) is Mexicos state-owned, nationalized petroleum company. ...

Recently, several craters around the world have been dated to approximately the same age as Chicxulub - for example the Silverpit crater in the United Kingdom and the Boltysh crater in Ukraine. This has led to the suggestion that the Chicxulub impact was one of several that occurred almost simultaneously, perhaps due to a disrupted comet impacting the Earth in a similar manner to the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994. Approximate location of the Silverpit crater The Silverpit crater is a crater located in the North Sea off the coast of the United Kingdom. ... The United Kingdom of Great Britain and Northern Ireland is a country in western Europe, and member of the Commonwealth of Nations, the G8, the European Union, and NATO. Usually known simply as the United Kingdom, the UK, or (inaccurately) as Great Britain or Britain, the UK has four constituent... Boltysh is a meteor crater in Ukraine. ... Ukraine (Україна, Ukrayina in Ukrainian; Украина in Russian) is a republic in eastern Europe which borders Russia to the east, Belarus to the north, Poland, Slovakia and Hungary to the west, Romania and Moldova to the southwest and the Black Sea to the south. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) Comet (disambiguation). ... Hubble Space Telescope image taken on May 17, 1994. ... Jupiter may refer to: Jupiter (god) – a Roman god Jupiter (planet) – a planet Jupiter Symphony – a symphony by Mozart, (Symphony No. ... 1994 was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ...

It was the lack of high concentrations iridium and shocked quartz which has prevented the acceptance of the idea that the Permian extinction (so-called mother of mass extinctions) was also caused by an impact. However, during the late Permian all the continents were combined into one supercontinent named Pangaea and all the oceans formed one superocean, Panthalassa. If an impact occurred in the ocean and not on land at all, then there would be little shocked quartz released (since oceanic crust has relatively little silica) and much less material. Dymaxion map by Buckminster Fuller shows land mass with minimal distortion as only one continuous continent A continent (Latin continere, to hold together) is a large continuous mass of land on the planet Earth. ... Map of Pangæa Pangaea (Greek for all lands) is the name Alfred Wegener used to refer to the supercontinent that existed during the Mesozoic era, before the process of plate tectonics separated the component continents. ... Panthalassa (Greek for all seas) was the vast ocean that surrounded the supercontinent Pangaea during the late Paleozoic era and the early Mesozoic era. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ...

Although there is now general agreement that there was a huge impact at the end of the Cretaceous that led to the iridium enrichment of the K-T boundary layer, remnants have been found of other impacts of the same order of magnitude that did not result in any mass extinctions, and in fact there is no clear linkage between an impact and any other incident of mass extinction.

Nonetheless it is now widely believed, if a little on faith, that mass extinctions due to impacts are an occasional event in the history of the Earth. One such controversial hypothesis is Tollmann's hypothetical bolide, which claims that the Holocene was initiated by an impact. Alexander Tollmanns bolide is a hypothesis presented by Austrian professor of geology Dr. Alexander Tollmann, suggesting that one or several bolides (asteroids or comets) struck the Earth at 7640 BCE (+/-200), with a much smaller one at 3150 BCE (+/-200). ... The Holocene Epoch is a geologic period that extends from the present back about 10,000 radiocarbon years. ...

Paleontologists Michael Raup and Jack Sepkoski have proposed that an extinction occurs roughly every 26 million years (though many are relatively minor). This led physicist Richard A. Muller to suggest that these extinctions could be due to a hypothetical companion star to the sun called Nemesis periodically disrupting the orbits of comets in the Oort cloud, and leading to a large increase in the number of comets reaching the inner solar system where they might hit Earth. Richard A. Muller(Born January 6, 1944) of San Francisco, California, USA, is a physicist who works at the University of California, Berkeley and Lawrence Berkeley National Laboratory. ... Nemesis is the name given to a hypothetical red dwarf star, magnitude between 7 and 12, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. ... This diagram shows the presumed distance of the Oort cloud compared to the rest of the solar system. ...

Indeed, in the early history of the Earth, about four billion years ago, bolide impacts were almost certainly common since the skies were far more full of "junk" than at present. Such impacts could have included strikes by asteroids hundreds of kilometers in diameter, with explosions so powerful that they vaporized all the Earth's oceans. It was not until this "hard rain" began to slacken, so it seems, that life could have begun to evolve on Earth. Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Ocean (Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ... For other uses, see Life (disambiguation) and Living (disambiguation). ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ...

The leading theory of Moon's origin is the giant impact theory, which states that Earth was once hit by a planetoid the size of Mars; possibly the largest impact Earth has ever suffered. Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Big Splash illustration The Big Splash The giant impact theory (or Big Splash or Big Whack; cf. ... Planetoid (meaning planet-like) is an old synonym of asteroids. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ...

Recent pre-historic impact events

In addition to the extremely large impacts that happen every few tens of millions of years, there are many smaller impacts that occur much more frequently but which leave correspondingly smaller traces behind. Due to the strong forces of erosion at work on Earth, only relatively recent examples of these smaller impacts are known. A few of the more famous or interesting examples are: Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and so forth) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ...

Barringer Crater, the first crater to be proven the result of an impact
the Rio Cuarto craters, produced by an asteroid striking Earth at a very low angle
the Wabar craters, which apparently formed within the past few hundred years
the Noerdlinger Ries, a 24-km crater in Central Europe, formed about 15 million years ago.

For the crater on the Moon, see the Lunar Barringer crater The Barringer Crater, also known as the Meteor Crater, is a famous impact crater created by a meteorite, located about 55 kilometers east of Flagstaff in the northern Arizona desert (USA). ... The Rio Cuarto craters are a group of depressions located in Argentina at lattitude S 32° 52, longitude W 64° 14 There is currently some controversy as to whether these structures are actually produced by impacts, or by aeolian surficial processes, which form many similar features in that region; this... The Wabar craters are meteorite craters found by accident by an explorer searching for the legendary city of Ubar The vast desert wasteland of southern Saudi Arabia known as the Empty Quarter, or Rub al Khali in Arabic, is one of the most desolate places on Earth. ... The Nördlinger Ries is a depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. ...

Modern impact events

The most significant recorded impact in recent times was the Tunguska event, which occurred at Tunguska in Russia, in 1908. But although the Tunguska event was both spectacular and unparalleled in any historical record, it no longer seems as unique and unusual as it once did. We now know that Earth impacts, including fairly big ones, are happening all the time. The Tunguska event was an aerial explosion that occurred at 60° 55’ North, 101° 57’ East, near the Podkamennaya (Stony) Tunguska River in what is now Evenkia, Siberia, at 7:17 AM on June 30, 1908. ... Tunguska (Тунгуска) is a remote, largely uninhabited region in Siberia, Russia. ... The Russian Federation (Russian: Росси́йская Федера́ция, transliteration: Rossiyskaya Federatsiya or Rossijskaja Federacija), or Russia (Russian: Росси́я, transliteration: Rossiya or Rossija), is a country that stretches over a vast expanse of eastern Europe and northern Asia. ... 1908 is a leap year starting on Wednesday (link will take you to calendar). ...

The late Eugene Shoemaker of the US Geological Survey came up with an estimate of the rate of Earth impacts, and suggested that an event about the size of the nuclear weapon that destroyed Hiroshima occurs about once a year. Such events would seem to be spectacularly obvious, but they generally go unnoticed for a number of reasons: the majority of the Earth's surface is covered by water; a good portion of the land surface is uninhabited; and the explosions generally occur at relatively high altitude, resulting in a huge flash and thunderclap but no real damage. The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Main keep of Hiroshima Castle The city of Hiroshima (広島市; -shi) is the capital of Hiroshima Prefecture, and the largest city in the Chugoku region of western Japan. ...

Some have been observed, such as the Revelstoke fireball of 1965, which occurred over the snows of northern Canada. Another fireball blew up over the Australian town of Dubbo in April 1993, shaking things up but causing no harm. Revelstoke was also the name of a well-known Canadian chain of hardware and home improvement stores, now known as Rona. ... Canada is a sovereign state in northern North America, the northern-most country in the world, and the second largest in total area. ... Australia, officially the Commonwealth of Australia, is the sixth-largest country in the world, the only country to occupy an entire continent, and the largest in the region of Australasia/Oceania. ... Dubbo is the largest population centre (population 38,000 as of 2004) and a Local Government Area in the central-west of New South Wales, Australia. ...

On the dark morning hours of January 18, 2000, a fireball exploded over the town of Whitehorse in the Canadian Yukon at an altitude of about 26 kilometers, lighting up the night like day and bringing down a third of the Yukon's electrical power grid, due to the electromagnetic pulse created by the blast. The meteor that produced the fireball was estimated to be about 4.6 meters in diameter and with a weight of 180 tonnes. January 18 is the 18th day of the year in the Gregorian Calendar. ... 2000 is a leap year starting on Saturday of the Gregorian calendar. ... Whitehorse is a Canadian city, the territorial capital of the Yukon. ... Motto: none Other Canadian provinces and territories Capital Whitehorse Largest city Whitehorse Commissioner Jack Cable Premier Dennis Fentie (Yukon Party) Area 482,443 km² (9th) - Land 474,391 km² - Water 8,052 km² (1. ... EMP redirects here. ...

A particularly interesting fireball was observed moving north over the Rocky Mountains from the US Southwest to Canada on August 10, 1972, and was filmed by a tourist at the Grand Teton National Park in Wyoming with an 8-millimeter color movie camera. The object was in the range of size from a car to a house and should have ended its life in a Hiroshima-sized blast, but there was never any explosion, much less a crater. Analysis of the trajectory indicated that it never came much lower than 58 kilometers off the ground, and the conclusion was that it had grazed Earth's atmosphere for about 100 seconds, then skipped back out of the atmosphere to return to its orbit around the Sun. Rocky Mountain National Park (photo courtesy of NPS) View of Colorado Rockies. ... August 10 is the 222nd day of the year (223rd in leap years) in the Gregorian Calendar. ... 1972 was a leap year that started on a Saturday. ... Grand Teton National Park is a United States National Park located in western Wyoming, south of Yellowstone National Park. ... State nickname: Equality State Other U.S. States Capital Cheyenne Largest city Cheyenne Governor Dave Freudenthal Official languages English Area 253,554 km² (10th) - Land 251,706 km² - Water 1,851 km² (0. ...

Comet Shoemaker-Levy 9 colliding with Jupiter

Many impact events occur without being observed by anyone on the ground. Between 1975 and 1992, American missile early warning satellites picked up 136 major explosions in the upper atmosphere. Hubble Space Telescope image taken on May 17, 1994. ...

The Tunguska event was about a thousand times more powerful than such events. Shoemaker estimated that one of such magnitude occurs about once every 300 years. This is not a long interval even by historical standards, and it is a somewhat nerve-wracking question to consider when the next "Big One" will be, and more to the point, where. The Tunguska event was an aerial explosion that occurred at 60° 55’ North, 101° 57’ East, near the Podkamennaya (Stony) Tunguska River in what is now Evenkia, Siberia, at 7:17 AM on June 30, 1908. ...

The 1994 impact of Comet Shoemaker-Levy 9 with Jupiter also served as a "wake-up call", and astronomers responded by starting programs such as Lincoln Near-Earth Asteroid Research (LINEAR), Near-Earth Asteroid Tracking (NEAT), Lowell Observatory Near-Earth Object Search (LONEOS) and several others which have drastically increased the rate of asteroid discovery. However, many objects undoubtedly still remain undetected. 1994 was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ... Hubble Space Telescope image taken on May 17, 1994. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... The Lincoln Near-Earth Asteroid Research (LINEAR) project is a cooperative project between the United States Air Force, NASA and MITs Lincoln Laboratory for the systematic discovery of near-Earth asteroids. ... Near Earth Asteroid Tracking (NEAT) is a program run by NASA and Jet Propulsion Laboratory to discover near-Earth objects. ... Lowell Observatory Near-Earth-Object Search (LONEOS) is a program run by NASA and Lowell Observatory to discover near-Earth objects. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ...

End of civilization

An impact event is commonly seen as a scenario¹ ² that would bring about the End of Civilization. In 2000 Discover Magazine published a list of 20 likely End of the world scenarios with impact event listed as the number one most likely to occur.³ Until the 1980s this idea was not taken seriously, but all that changed after the discovery of the Chicxulub Crater which was further reinforced by witness to the Comet Shoemaker-Levy 9 event. Since then there has been a lot more interest and funding of studies. This article contains a list of potential causes of the end of civilization, centered on non-religious concepts. ... Discover Magazine is a science magazine that publishes articles about science. ... This article is about the religious concept. ...

Notes

Note 1: Armageddon Online (http://www.armageddononline.org/asteroid.php). End of civilization scenario.
Note 2: Exit Mundi (http://www.exitmundi.nl/Comets.htm). End of civilization scenario.
Note 3: "Twenty ways the world could end suddenly" (http://www.findarticles.com/p/articles/mi_m1511/is_10_21/ai_65368918). Discover Magazine.

Discover Magazine is a science magazine that publishes articles about science. ...

External links

Earth impacts (http://www.vectorsite.net/taimpact.html)
Earth Impact Database (http://www.unb.ca/passc/ImpactDatabase/index.html)
Earth Impact Effects Program (http://www.lpl.arizona.edu/impacteffects/)

The geology of Earth-impact events GA_googleFillSlot("encyclopedia_square");