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1. Introduction 2. Body - meteors in popular culture - impacts - Tunguska event - major meteor impacts theory - Chixulub - future impact forecasts, Apophis 3. Conclusion Meteorite Impacts on Earth Meteorite impacts have always affected the Earths history, but only during the second half of the 20 th century astronomers and geologists have found and proved this. The existence of meteorites was not recognized by leading scientists of some 100 years ago.
The hypothesis of objects of extraterrestrial origin reaching the Earth was considered pseudo-scientific. Even Paris Academy of Sciences in 1790 decided not to consider further reports of falling rocks on Earth as such phenomenon was impossible. A meteoroid enters the Earths atmosphere at speeds of about 11 - 25 km / sec . At such speeds it starts his warm-up and glow. Due to burning and blowing off the oncoming stream of particles the weight of an object reaching the surface significantly decreases. Majority of small meteoroids entering the atmosphere at a speed of 25 km / sec burn down completely.
Only a few kilograms or even grams of the can reach the surface out of tens of tons entering at such speeds. Meteorite impacts is a continuous process that has an influence on life on our planet. Barringer Crater in Arizona, was the first crater to be scientifically proven as the result of an impact by Eugene Shoemaker in 1963. Since then scientists research craters worldwide and came up with new approaches analyzing the past of our planet.
Meteor impacts became key factors influencing sudden changes on the Earth. With the onset of the Space Age, humankind realized that the Earth was under constant threat from celestial bodies. (Bagrov) It is important today to predict when a large meteor reaching the planet and to find how to avoid a major impact. Nowadays, we watch TV programs about meteorite impacts and craters, read magazines that present various ideas on how life on the Earth changed because of major impacts in the past. Moreover, the belief that a major meteor impact may happen in the near future is existing in the popular culture, especially after being presented in Hollywood's Armageddon.
Small meteors frequently collide with the Earth and cause no threat. It is believed that large impacts that have great influence on the planet occur once every 500, 000 years (Bostrom, 2002). Meteors with diameter 5 - 10 meters reach the Earth once a year, but they explode in the atmosphere and rarely reach the Earth. An serious impact event is a process which causes instant geologic change. The landscape is transformed by an intense explosion. Tunguska event is the most recent example of a relatively big meteor reaching the Earth.
In 1908 the meteor exploded at a height of 7 km above the Earths surface. The air blast flattened trees over an area of about 2000 km 2. Had such an event taken place above one of our major cities the ensuing devastation would have concentrated the minds of Earth scientists on our greatest natural hazard. (Hancock & Skinner, 2000) Although the meteor did not hit the ground directly, this event is still referred to as an impact. It is a known fact that the Earth has gone through periods of sudden and catastrophic change.
If a large meteorite slammed into the earth, it would turn rock into dust. The dust could have the effect of turning day into night on Earth for years. (Alvarez) Scientists propose a theory that each change had been caused only by the major meteor impact. The idea that such impacts caused massive climate change and extinction of species is well-supported. Today scientists have suggested that the origins of life may have been influenced by impacting objects bringing organic chemicals or life forms to the Earths surface. In 1991 Alan Hilderbrand, of the University of Arizona, published his research confirming the existence of a 180 kilometers wide meteorite crater off the coast of the Yucatan Peninsula in Mexico. Hilderbrand shows evidence that the impact, named the Chixulub, occurred 60 - 65 million years ago.
This time boundary is known as the second largest extinction event in Earths history, and is most notably known for the loss of dinosaurs. The discovery of Chixulub stimulated further research and debate as to the exact role the Chixulub event had on climate change and global mass extinction. Such an impact is thought to be responsible for the mass extinction of many floral and faunal species, including the large dinosaurs, that mark the termination of the Cretaceous period. (Duller) The evidence at Chixulub and possibility of other impact-related extinctions remains a mystery and probably will never be proved completely. In 2004 the new asteroid 99942 Apophis has been discovered.
The size is approximately 320 m. This asteroid has been regarded as potentially dangerous, but after later calculations astronomers found that Apophis will miss earth by 25, 000 km in 2029. The asteroids orbit can be changed unpredictably even by the Earths gravitation in a way which does not rule out a collision on April 13 or 14, 2036. Consequences of collision of a meteor like Apophis with the Earth are unpredictable. An impact several thousand miles off the West Coast of the US would produce a devastating tsunami. (Noland 2006) Thanks to the recent researches on meteor impacts on earth new approaches towards the history of our planet were developed. Meteors were and will be hitting our planet.
The examination of the meteor impacts as processes acting on our planet will help to understand the past and predict the future of the Earth. Bibliography: Bagrov, Alexander. The Tunguska Meteorite As A Warning From Outer Space (2008) web Bostrom, Nick. Existential Risks: Analyzing Human Extinction Scenarios and Related Hazards." Journal of Evolution and Technology 9. (2002) web Hancock Paul, Skinner Brian.
The Oxford Companion to the Earth (2000) web Noland, David The Threat is Out There. Popular Mechanics. (2006) web Retrieved 2008 - 02 - 22. Duller, Charles. The Meteor Impact that Killed the Dinosaurs? web Alvarez, Award, & Michel. Possible Effects of Large Meteor Hitting Earth (1980)
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