NationMaster - Encyclopedia: Impact event

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 weapons 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. ... For other uses, see Collision (disambiguation). ... â€œMeteorâ€ redirects here. ... For other uses, see Asteroid (disambiguation). ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... â€œMeteorâ€ redirects here. ... This article is about Earth as a planet. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... Tycho crater on Earths moon. ...

1 The geology of Earth-impact events
2 Mass extinctions and impacts
3 Recent pre-historic impact events
4 Modern impact events
5 Near misses and forecasts
6 End of civilization
7 Fictional impact events
8 Notes
9 See also
10 External links
11 Further reading

The geology of Earth-impact events

The Earth has 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 Moon is widely attributed to be the result of a huge impact early in Earth's history. Impact events even earlier in the history of Earth 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, a theory known as panspermia. For other uses, see Extinction (disambiguation). ... For other uses, see Species (disambiguation). ... This article is about Earths moon. ... The Big Splash redirects here. ... Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Animated map exhibiting the worlds oceanic waters. ... This article focuses on modern scientific research on the origin of life. ... Panspermia is a proven process (based on the principles of Biology, Microbiology, Physics, Chemistry, Astronomy, and assumption that life existed already in the universe) that explains how all life in the universe and/or solar system comes from a seed of life. ...

Eugene Merle Shoemaker was first to prove that meteor impacts have affected the Earth.

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 Peaks stand only 30 miles to the west). Similarly, the craters on the surface of the Moon were ascribed to volcanism. USGS photo of Eugene Shoemaker. ... USGS photo of Eugene Shoemaker. ... Eugene Shoemaker at a stereoscopic microscope used for asteroid discovery Eugene Shoemaker wearing a Bell rocket belt while training astronauts. ... Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ... This article is about Earth as a planet. ... 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). ... Official language(s) English Spoken language(s) English 74. ... This article is about volcanoes in geology. ... The San Francisco Peaks, with the Wupatki National Monument in the foreground Composite image of the mountains, from satellite imagery projected onto an elevation model. ...

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. In 1994, the first major impact event was directly observed: the collision of the comet Shoemaker-Levy 9 with Jupiter; to date, no such events have been observed on Earth. Year 1903 (MCMIII) was a common year starting on Thursday (link will display calendar) of the Gregorian calendar or a common year starting on Wednesday of the 13-day slower Julian calendar. ... For other uses, see 1905 (disambiguation). ... For other uses, see 1963 (disambiguation). ... Eugene Shoemaker at a stereoscopic microscope used for asteroid discovery Eugene Shoemaker wearing a Bell rocket belt while training astronauts. ... Twentieth century redirects here. ... Space exploration is the physical exploration of outer space, both by human spaceflights and by robotic spacecraft. ... Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...

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 10,000,000 (ten 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. Tycho crater on Earths moon. ... This article is about Earths moon. ... Astrogeologist and NASA astronaut Harrison Jack Schmitt collecting lunar samples during the Apollo 17 mission Astrogeology is a planetary science discipline concerned with the geology of the celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. ... This article is about Earth as a planet. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Site of the detonation. ...

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 in the Permian-Triassic, which ended the Permian period 250 million years ago and killed off 90% of all species.^[1] 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 extinction event. There is no solid evidence of impacts leading to the four other major mass extinctions, though a recent report from Ohio State scientists stated that they have located a 483-km diameter impact crater beneath the East Antarctic Ice Sheet which may date back about 250 million years, based on gravity measurements, which might associate it with the Permian-Triassic extinction event. An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... For other uses, see Species (disambiguation). ... This article is about the tv programme Life on Earth. ... The Permian-Triassic (P-T or PT) extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 251 million years ago (mya), forming the boundary between the Permian and Triassic geologic periods. ... The Permian is a geologic period that extends from about 299. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... For other uses, see Asteroid (disambiguation). ... Artists impression of a major impact event. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ...

In 1980, physicist Luis Alvarez, his son, geologist Walter Alvarez, and nuclear chemists Frank Asaro and Helen V. Michael from the University of California, Berkeley 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. Portrait of Luis Alvarez Luis Walter Alvarez (June 13, 1911 â€“ September 1, 1988) of San Francisco, California, USA, was a famed physicist of Spanish descent, 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. ... Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... This article is about the chemical element. ... Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ... 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, Pigment Black 7, carbon black or black carbon, 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 smokeâ€”especially from the combustion of carbon-rich organic fuels in the...

Anomalies in chromium isotopic ratios found within the K-T boundary layer strongly support the impact theory.^{[citation needed]} Chromium isotopic ratios are homogeneous within the earth, therefore these isotopic anomalies exclude a volcanic origin which was also proposed as a cause for the iridium enrichment. Furthermore the chromium isotopic ratios measured 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 Yucatán 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 (IPA: ) (cheek-shoo-LOOB) is an ancient impact crater buried underneath the YucatÃ¡n Peninsula, with its center located approximately underneath the town of Chicxulub, YucatÃ¡n, Mexico. ... The YucatÃ¡n peninsula as seen from space The YucatÃ¡n Peninsula, in Southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico. ... Geophysics, the study of the earth by quantitative physical methods, especially by seismic reflection and refraction, gravity, magnetic, electrical, electromagnetic, and radioactivity methods. ... Petro redirects here. ... A Pemex gas station in Puerto Vallarta PetrÃ³leos 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 sub-sea structure under the North Sea off the coast of the United Kingdom. ... Location of the Boltysh Crater The Boltysh Crater is an impact crater in Ukraine. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ...

It was the lack of high concentrations of 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. None of this takes into account the East Antarctic Ice Sheet crater, which is a recent find. Animated, colour-coded map showing the various continents. ... For other uses, see Pangaea (disambiguation). ... 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 Earth. One such controversial hypothesis is Tollmann's hypothetical bolide, which claims that the Holocene was initiated by an impact. Geological time put in a diagram called a geological clock, showing the relative lengths of the eons of the Earths history. ... Alexander Tollmanns bolide, proposed by Kristen-Tollmann and Tollmann (1994), 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 (Â±200), with a much smaller one at 3150 BCE (Â±200). ... The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. ...

Paleontologists David M. 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. David M. Raup is a University of Chicago paleontologist. ... J. John Sepkoski Jr. ... Richard Muller Richard A. Muller (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 a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. ... Artists rendering of the Oort cloud and the Kuiper Belt. ...

Indeed, in the early history of the Earth, about four billion years ago, bolide impacts were almost certainly common since the solar system was full of far more material 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 heavy bombardment began to slacken, so it seems, that life could have begun to evolve on Earth. This article is about Earth as a planet. ... For other uses, see Asteroid (disambiguation). ... This article is about Earth as a planet. ... Animated map exhibiting the worlds oceanic waters. ... This article is about life in general. ... This article is about Earth as a planet. ...

The leading theory of the Moon's origin is the giant impact theory, which states that Earth was once hit by a planetoid the size of Mars; if this theory holds then that impact was almost certainly the largest hit Earth ever suffered. This article is about Earths moon. ... The Big Splash The giant impact theory (or Big Splash or Big Whack; cf. ... Look up Planetoid in Wiktionary, the free dictionary. ... 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: For morphological image processing operations, see Erosion (morphology). ...

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 around 10,000 years ago
the Henbury crater, in Australia, and Kaali crater in Estonia, apparently produced by objects which broke up before impact. Both are estimated to be 4000-5000 years old.
the Wabar craters, which apparently formed within the past few hundred years

More recent prehistoric impacts are theorized (Ancient Crash, Epic Wave by Sandra Blakeslee, New York Times, 14 Nov 2006) by the Holocene Impact Working Group, including Dallas Abbott of Lamont-Doherty Earth Observatory in Palisades, N.Y. This group points to four enormous chevron sediment deposits at the southern end of Madagascar, containing deep-ocean microfossils fused with metals typically formed by cosmic impacts. All of the chevrons point toward a spot in the middle of the Indian Ocean where newly discovered Burckle crater^[2], 18 miles in diameter, lies 12,500 feet below the surface. This group posits that a large asteroid or comet impact 4,500--5,000 years ago, produced a mega-tsunami at least 600 feet high. If this and other recent impacts prove correct, the rate of asteroid impacts is much higher than currently thought. 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... Henbury is a meteor crater in Northern Territory, Australia. ... The main crater is nearly circular. ... 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 Fenambosy Chevron is one of four chevron-shaped land features on the southwest coast of Madagascar, near the tip of Madagascar, 600 feet (180 m) high and three miles (5 km) from the ocean. ... Burckle Crater is an undersea crater likely to have been formed by a very large scale comet or meteorite impact event. ... 2900 BC â€“ 2334 BC â€” Mesopotamian wars of the Early Dynastic period. ...

Holocene impact events have been proposed by the dendrochronologist Mike Baillie as a possible cause of several brief (typically 5-10 year) climatic downturns recorded in ancient tree ring patterns. In his book 'Exodus to Arthur: Catastrophic encounters with comets' he highlights for such events and suggests that these might have been caused by the dust veils thrown up by the impact of cometary debris. The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. ... The growth rings of an unknown tree species, at Bristol Zoo, England Pinus taeda Cross section showing annual rings, Cheraw, South Carolina Pine stump showing growth rings Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree-ring growth patterns. ...

Modern impact events

In China’s Shanxi Province, 10,000 people were said to have been killed in 1490 by a hail of "falling stones" that some astronomers surmise may have been triggered by the breakup of a large asteroid.^[3] Not to be confused with the neighboring province of Shaanxi Shanxi (Chinese: 山西; pinyin: Shānxī; Wade-Giles: Shan-hsi; Postal System Pinyin: Shansi) is a northern province of the Peoples Republic of China. ... Events Tirant Lo Blanc by Joanot Martorell, MartÃ Joan De Galba is published. ...

The most significant recorded impact in recent times was the Tunguska event, which occurred in Siberia, Russia, in 1908. This incident involved an explosion that was probably caused by the airburst of an asteroid or comet 5 to 10 kilometers (3–6 mi) above the Earth's surface, felling an estimated 80 million trees over 2,150 square kilometers (830 sq mi). 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. Trees felled by the Tunguska blast. ... This article is about Siberia as a whole. ... Year 1908 (MCMVIII) was a leap year starting on Wednesday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Tuesday of the 13-day-slower Julian calendar). ...

The late Eugene Shoemaker of the U.S. 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. InsertSLUTTY WHORESâ‰¤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... For other uses, see Hiroshima (disambiguation). ...

Some have been observed. Noteworthy examples include the Sikhote-Alin Meteorite fall in Primorye, far eastern Russia, in 1947, and the Revelstoke fireball of 1965, which occurred over the snows of British Columbia, Canada. Another fireball blew up over the Australian town of Dubbo in April 1993, shaking things up but causing no harm. A 1. ... The Primorsky Krai (Russian: Примо́рский край), also known as Primorye (Примо́рье), is one of Russias 89 federal subjects (also referred to as members of the Federation). Krai is... Revelstoke was also the name of a well-known Canadian chain of hardware and home improvement stores, now known as Rona. ... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area Ranked 5th Total 944... For the seat in the New South Wales Legislative Assembly, see Electoral district of Dubbo. ...

A small number of meteorite falls have been observed with automated cameras and recovered following calculation of the impact point. The first of these was the Pribram meteorite, which fell in Czechoslovakia (now the Czech Republic) in 1959.^[4] In this case, two cameras used to photograph meteors captured images of the fireball. The images were used both to determine the location of the stones on the ground and, more significantly, to calculate for the first time an accurate orbit for a recovered meteorite. Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... Location of PÅ™Ãbram within Czech Republic. ... Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...

Following the Pribram fall, other nations established automated observing programs aimed at studying infalling meteorites. One of these was the Prairie Network, operated by the Smithsonian Astrophysical Observatory from 1963 to 1975 in the midwestern US. This program also observed a meteorite fall, the Lost City chondrite, allowing its recovery and a calculation of its orbit.^[5] Another program in Canada, the Meteorite Observation and Recovery Project, ran from 1971 to 1985. It too recovered a single meteorite, Innisfree, in 1977.^[6] Finally, observations by the European Fireball Network, a descendant of the original Czech program that recovered Pribram, led to the discovery and orbit calculations for the Neuschwanstein meteorite in 2002.^[7] The Smithsonian Astrophysical Observatory (SAO) is a research institute of the Smithsonian Institution headquartered in Cambridge, Massachusetts, where it is joined with the Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center for Astrophysics (CfA). ... For other uses, see 1963 (disambiguation). ... Year 1975 (MCMLXXV) was a common year starting on Wednesday (link will display full calendar) of the Gregorian calendar. ... Year 1971 (MCMLXXI) was a common year starting on Friday (link will display full calendar) of the 1971 Gregorian calendar, known as the year of cyclohexanol. ... This article is about the year. ... Also: 1977 (album) by Ash. ... Neuschwanstein seen from the MarienbrÃ¼cke. ...

The only reported fatality from meteorite impacts is an Egyptian dog who was killed in 1911 by the Nakhla meteorite, although this report is disputed. The meteorites that struck this area were identified in the 1980s as Martian in origin. Year 1911 (MCMXI) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Saturday of the 13-day-slower Julian calendar). ... The Nakhla meteorite, the first and eponymous example of a Nakhlite type meteorite of the SNC Group type of meteorites, fell to Earth on the 28th of June, 1911, at approximately 09:00 in the Nakhla region of Abu Hommos, Alexandria, Egypt. ... The 1980s refers to the years from 1980 to 1989. ... Adjectives: Martian Atmosphere Surface pressure: 0. ...

The first known modern case of a human hit by a space rock [1] occurred on November 30, 1954 in Sylacauga, Alabama. There a 4 kg stone chondrite [2] crashed through a roof and hit Ann Hodges in her living room after it bounced off her radio. She was badly bruised. Several persons have since claimed [3] to have been struck by 'meteorites' but no verifiable meteorites have resulted. This article is about modern humans. ... is the 334th day of the year (335th in leap years) in the Gregorian calendar. ... Year 1954 (MCMLIV) was a common year starting on Friday (link will display full calendar) of the Gregorian calendar. ... Sylacauga is a city located in Talladega County, Alabama. ... YAYAYAYAYAYAnn Elizabeth Hodges (1923 - 1972) of Sylacauga, Alabama is the only person of record to have been hit by a meteorite. ...

A particularly interesting fireball was observed moving north over the Rocky Mountains from the U.S. 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^{[citation needed]}. 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. For individual mountains named Rocky Mountain, see Rocky Mountain (disambiguation). ... is the 222nd day of the year (223rd in leap years) in the Gregorian calendar. ... Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ... Grand Teton National Park is a United States National Park located in western Wyoming, south of Yellowstone National Park. ... Official language(s) English Capital Cheyenne Largest city Cheyenne Area Ranked 10th - Total 97,818 sq mi (253,348 kmÂ²) - Width 280 miles (450 km) - Length 360 miles (580 km) - % water 0. ...

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. The meteor that produced the fireball was estimated to be about 4.6 meters in diameter and with a weight of 180 tonnes. This blast was also featured on the The Science Channel series Killer Asteroids, with several witness reports from residents in Atlin, British Columbia. is the 18th day of the year in the Gregorian calendar. ... Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... Whitehorse (IPA: /ÊaÉªt. ... This article is about Yukon Territory in Canada. ... The Science Channel is a television channel spin-off from the Discovery Channel, which features only science-related television shows. ... Atlin is a community in northwestern British Columbia, Canada, located on Atlin Lake. ...

A meteor was observed striking Reisadalen in Nordreisa municipality in Troms County, Norway, on June 7, 2006. Although initial witness reports stated that the resultant fireball was equivalent to the Hiroshima nuclear explosion, scientific analysis places the force of the blast at anywhere from 100-500 tonnes TNT equivalent—at most, around 3% of Hiroshima's yield. [4] County Troms District Municipality NO-1942 Administrative centre Storslett Mayor (2003) John Karlsen (Frp) Official language form BokmÃ¥l Area - Total - Land - Percentage Ranked 9 3,438 kmÂ² 3,344 kmÂ² 1. ... County NO-19 Region Nord-Norge Administrative centre TromsÃ¸ County mayor Area - Total - Percentage Ranked 4 25,877 kmÂ² 8. ... is the 158th day of the year (159th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... This article is about the metric tonne. ...

Comet Shoemaker-Levy 9's scar on Jupiter (Dark area at the above-left of the image)

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. In the 21-Nov-2002 edition of the journal Nature, Peter Brown of the University of Western Ontario reported on his study of US early warning satellite records for the proceeding 8 years. He identified 300 flashes caused by 1m to 10m sized meteors in that time period and estimated the rate of Tunguska sized events as once in 400 years [5]. Shoemaker estimated that one of such magnitude occurs about once every 300 years, though more recent analyses have suggested he exaggerated by an order of magnitude. Even at that, this is not a long interval, and it is a somewhat nerve-wracking question to consider when the next "Big One" will be, and more to the point, where. Image File history File links Impact_site_of_fragment_G.gif Impact site of fragment G of Comet Shoemaker-Levy 9 on Jupiter. ... Image File history File links Impact_site_of_fragment_G.gif Impact site of fragment G of Comet Shoemaker-Levy 9 on Jupiter. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ... Trees felled by the Tunguska blast. ...

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. Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, 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. ... For other uses, see Asteroid (disambiguation). ...

On September 15, 2007, a chondritic meteor crashed into southeastern Peru near Lake Titicaca, leaving a water-filled hole and spewing gases across the surrounding area. Many residents became ill from the noxious gases shortly after the impact. is the 258th day of the year (259th in leap years) in the Gregorian calendar. ... A specimen of the NWA 869 chondrite (type L4-6), showing chondrules and metal flakes Chondrites are stony meteorites that have not been modified due to melting or differentiation of the parent body. ... The crash site. ... Lake Titicaca sits 3,812 m (12,507 feet) above sea level making it the highest commercially navigable lake in the world. ...

Near misses and forecasts

On 19 May 1996 a 300–500-m asteroid, 1997 JA1, passed within 450,000 km of Earth; it had been detected a few days before. is the 139th day of the year (140th in leap years) in the Gregorian calendar. ... Year 1996 (MCMXCVI) was a leap year starting on Monday (link will display full 1996 Gregorian calendar). ...

On 18 March 2004 a 30-m asteroid, 2004 FH, passed within 40,000 km of Earth only a few days after it had been detected. This asteroid probably would have detonated in the atmosphere and posed negligible hazard to the surface, had it been on impact course. is the 77th day of the year (78th in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... 2004 FH is a near-Earth asteroid that was discovered on March 15, 2004 by the NASA-funded LINEAR asteroid survey. ...

On 31 March 2004, a 6m meteoroid, 2004 FU162 made the closest near miss pass ever observed with a separation of only 1.02 Earth radii from the surface (6,500 km). Because this object is certainly too small to pass through the atmosphere, it is classed as a meteoroid rather than an asteroid. is the 90th day of the year (91st in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... â€œMeteorâ€ redirects here. ... 2004 FU162 (also written 2004 FU162) is a meteoroid which passed within about one Earth radius of the surface of the Earth at 15:35 UTC on March 31, 2004, or 2. ...

In 2004, a newly discovered 320-m asteroid, 99942 Apophis (previously called 2004 MN4), achieved the highest impact probability of any potentially dangerous object. The probability of collision on 13 April 2029 was estimated to be as high as 1 in 17 by Steve Chesley of NASA's Jet Propulsion Laboratory though the worst published figure was 1 in 37 calculated in December 2004. Later observations showed that the asteroid will miss the earth by 25,600 km (within the orbits of communications satellites) in 2029, but its orbit will be altered unpredictably in a way which does not rule out a collision on 13 or 14 April 2036 or later in the century. These possible future dates have a cumulative probability of 1 in 45,000 for an impact in the 21^stcentury. Close approach of Apophis on April 13, 2029 The white bar indicates uncertainty in the range of positions 99942 Apophis (99942) Apophis (previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a... 2029 (MMXXIX) will be a common year starting on Monday of the Gregorian calendar. ... The National Aeronautics and Space Administration (NASA) (IPA [ËˆnÃ¦sÉ™]) is an agency of the United States government, responsible for the nations public space program. ... For the singer/songwriter, see Jon Peter Lewis. ...

Asteroid 2004 VD17, of 580 m, previously was estimated to have a probability of 1 in 63,000 of striking earth on 4 May 2102 (as of July 2006), with risk 1 on the Torino scale, but further observations lowered the estimate. As of the observation on December 17, 2006, JPL assigns 2004 VD17 a Torino value of 0 and an impact probability of 1 in 41.667 million in the next 100 years. 2004 VD17 (also written 2004 VD17) is a near-Earth asteroid with a low but non-zero probability of impacting Earth in 2102. ... The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. ... December 17 is the 351st day of the year (352nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

Asteroid (29075) 1950 DA is predicted to collide with Earth on March 16, 2880. The probability of impact is either 1 in 300 or zero, depending on which one of the two possible directions for the asteroid's spin pole is correct. This asteroid has a mean diameter of about 1.1 km. The energy released by the collision would cause major effects on the climate and biosphere and may be devastating to human civilization. Asteroid 1950 DA, radar image (29075) 1950 DA is the near Earth object with the highest known possible probability of impacting Earth, according to the Palermo Technical Impact Hazard Scale. ...

Relatively small objects that burn up in the atmosphere can be dangerous beyond their own capabilities. In 2002, U.S. Air Force Brig. Gen. Simon P. Worden told members of a U.S. House of Representatives Science subcommittee that the U.S. has instruments that determine if an atmospheric explosion is natural or man-made, but no other nation with nuclear weapons has that detection technology. He said there is concern that some of those countries could mistake a natural explosion for an attack, and launch nuclear retaliation. In the summer of 2001 U.S. satellites had detected over the Mediterranean an atmospheric flash of energy similar to a nuclear weapon, but determined that it was caused by an asteroid. Seal of the Air Force. ... The House of Representatives is the larger of two houses that make up the U.S. Congress, the other being the United States Senate. ... The Mediterranean Sea is an intercontinental sea positioned between Europe to the north, Africa to the south and Asia to the east, covering an approximate area of 2. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ...

End of civilization

An impact event is commonly seen as a scenario^[8] ^[9] 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.^[10] 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 more interest from the scientific community and greater public awareness of the possibility of impact events. The end of civilization or the end of the world are phrases used in reference to human extinction scenarios, doomsday events, and related hazards which occur on a global scale. ... Discover Magazine is a science magazine that publishes articles about science. ... The end of planet Earth refers to hypotheses of when the Earth either completely ceases to exist as a planet or becomes uninhabitable for life. ... Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater (IPA: ) (cheek-shoo-LOOB) is an ancient impact crater buried underneath the YucatÃ¡n Peninsula, with its center located approximately underneath the town of Chicxulub, YucatÃ¡n, Mexico. ... Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. ...

Fictional impact events

The impact event has been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream. Interestingly, it seems, by survey, to be one of the less popular themes in apocalyptic science fiction compared to other possible catastrophes. Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... Apocalyptic science fiction is a sub-genre of science fiction that is concerned with the end of civilization, through nuclear war, plague, or some other general disaster. ...

Numerous science fiction stories and novels center around an impact event; possibly the best selling was the novel Lucifer's Hammer by Larry Niven and Jerry Pournelle. Arthur C. Clarke's novel Rendezvous with Rama opens with a significant asteroid impact in northern Italy in the year 2077 which gives rise to the Spaceguard Project, which later discovers the Rama spacecraft. In 1992 a Congressional study in the U.S.A. led to NASA being directed to undertake a 'Spaceguard Survey' (with the novel being named as the inspiration for the name[6]) to search for Earth-impacting asteroids. This in turn inspired Clarke's 1993 novel The Hammer of God. A variation on the traditional impact story was provided by Jack McDevitt's 1999 novel Moonfall, in which a very large comet travelling at interstellar velocities collides with and partially destroys the Moon, fragments of which then collide with the Earth. Lucifers Hammer is a post-apocalyptic science fiction novel by Larry Niven and Jerry Pournelle, first published in 1977. ... This article does not cite any references or sources. ... Jerry Eugene Pournelle, Ph. ... Wikiquote has a collection of quotations related to: Arthur C. Clarke Sir Arthur Charles Clarke, CBE (born 16 December 1917) is a British science-fiction author and inventor, most famous for his novel 2001: A Space Odyssey, and for collaborating with director Stanley Kubrick on the film of the same... Rendezvous with Rama is a novel by Arthur C. Clarke first published in 1972. ... The term Spaceguard loosely refers to a number of efforts to discover and study near-Earth objects (NEO). ... The Hammer of God is a science fiction novel written by Arthur C. Clarke in 1993. ... Jack McDevitt (1935-) is an American science fiction author whose novels frequently deal with attempts to make contact with alien races and archaeology (or xenoarchaeology). ...

Several disaster movies have also been made, including When Worlds Collide (1951), and Meteor (1979). More recently, in 1998 two high-budget action films were based on preventing extinction-level impact events, caused by different bolides: Deep Impact (a seven-mile-wide comet, later split into two objects 6 mi. and 1.5 mi. wide) and Armageddon (an asteroid described as "the size of Texas". Also in 1998, the award-winning Canadian film Last Night described the behavior of several characters anticipating the end of the world due to some certain but unstated peril with a known due date - thus resembling a civilzation terminating impact event. With the release of The Poseidon Adventure (1972), the Disaster film officially became a movie-going craze. ... When Worlds Collide DVD cover This article is about the 1951 film. ... Year 1951 (MCMLI) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar. ... Meteor (1979) is a film in which scientists detect an asteroid on a collision course with Earth and struggle with international, cold war politics in their efforts to prevent disaster. ... Also: 1979 by Smashing Pumpkins. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... Deep Impact is a 1998 science fiction disaster film released by Paramount Pictures and DreamWorks Pictures. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... This article or section contains a plot summary that is overly long or excessively detailed compared to the rest of the article. ... For other uses, see Asteroid (disambiguation). ... For other uses, see Texas (disambiguation). ... Last Night is a 1998 Canadian film by Don McKellar. ...

In 1968, episode 58 of the ever popular Star Trek series aired. The episode, entitled "The Paradise Syndrome," involved the crew of the Starship Enterprise endeavoring to alter the trajectory of a moon-sized asteroid so as to prevent a disastrous collision with a planet that lie in its path. Interestingly, the inhabitants of the doomed planet are represented by a culture indistinguishable from the pre-Columbian indians of North America. This fictional account from 1968 is chillingly similar to a scenario modern-day scientists (2001 to 2007) propose played out with respect to the paleo-indians of North America (Clovis) when they were overtaken by a massive comet that struck somewhere in the northern hemisphere and initiated the Younger Dryas period that occurred at the end of the last ice age. The collision is also believed to have played a significant part in the mass extinction of some 35 genera of mammals (megafauna).

Also in 1968, a joint Japanese-American venture between Toei and MGM resulted in the release of "The Green Slime," which chronicled the exploits of a group of astronauts as they race to rendezvous with an asteroid on a collision course with Earth. The astronauts touch down on the surface of the asteroid where they proceed to plant a powerful explosive device that disintegrates the object. Thirty years later, Touchtone Pictures (Disney) released "Armageddon," which chronicled an identical mission to explode an incoming projectile the size of Texas.

A small impact event in the Command & Conqer "Tiberium" series of videogames caused the deadly mineral Tiberium to spread across the Earth resulting in 3 world wars, killing millions. The actual impact was very small, and landed near the Tiber river in Italy.

Notes

^ Permian Extinction
^ Meteor 'misfits' find proof in sea. Retrieved on 2006-11-14.
^ Meteorite Impact Structures Student Research
^ Ceplecha, Z. (1961) Multiple fall of Pribram meteorites photographed. Bull. Astron. Inst. Czechoslovakia, 12, 21-46 NASA ADS
^ McCrosky, R.E. et al. (1971) J. Geophys. Res. 76, 4090-4108
^ Campbell-Brown, M. D. and Hildebrand, A. (2005) A new analysis of fireball data from the Meteorite Observation and Recovery Project (MORP). Earth, Moon, and Planets 95, 489 - 499
^ Oberst, J. et al. (2004) The multiple meteorite fall of Neuschwanstein: Circumstances of the event and meteorite search campaigns. Meteoritics & Planetary Science 39, 1627-1641 NASA ADS
^ Armageddon Online. End of civilization scenario.
^ Exit Mundi. End of civilization scenario.
^ "Twenty ways the world could end suddenly". Discover Magazine.

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 318th day of the year (319th in leap years) in the Gregorian calendar. ... Discover Magazine is a science magazine that publishes articles about science. ...

External links

EARTH IMPACTS from Greg Goebel's IN THE PUBLIC DOMAIN
Earth Impact Database
Earth Impact Effects Program
Aerial Explorations of Terrestrial Meteorite Craters
All 172 confirmed meteor impact sites on earth, viewable in Google Earth (Largest, Most recent, Per continent, Including size indicator)
Neosafety Foundation
Reorienting Western Society to Battle Impact Events Jagiellonian University, Poland
A comet or asteroid impact with the earth - How real is the threat? Bob Hawkes
arguing for a globally cooperative Earth Defense Initiative (EDI)
Traces of Catastrophe
GEOSIM - Information on impact processes and effects; 3-D-simulation

Contents

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