An impact winter is a period of prolonged cold weather caused by the impact on the Earth of a large asteroid or comet. If such an impact occurred on land or the floor of a shallow sea, it could cause large amounts of dust or ash to be thrown into the Earth's atmosphere, blocking the Sun's light and dramatically lowering the amount of sunlight reaching the earth's surface. An impact winter is one of the mechanisms proposed for extinction events, such as the asteroid impact at Chicxulub in Mexico which may have lead to the extinction of the dinosaurs. There is little concrete geological evidence, however, that a significant impact winter has occurred in the past. An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Comet Hale-Bopp For other uses, see Comet (disambiguation). ... An extinction event (also extinction-level event, ELE) occurs when a large number of species die out in a relatively short period of time. ... 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, Yucatán, Mexico. ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ...

Depending on the size of the object, and the location and angle at which it hits the earth, material can be thrown into the atmosphere by two mechanisms:

1. The impact could eject large amounts of regolith (and perhaps shattered bedrock) into the atmosphere
2. The impact could strike a heavily forested area such as Amazonia or Siberia. The resulting fireball could spark a massive fire, throwing up large amounts of smoke and ash into the atmosphere.

The latter scenario is the more dangerous, as the lighter particles from the fire would take weeks or months to fall back to earth, and could be distributed by jet streams around the world, making the cooling a global event. Regolith (Greek: blanket rock) is a layer of loose, heterogeneous material covering solid rock. ... Bedrock is the native consolidated rock underlying the Earths surface. ... A river in the Amazon rainforest The Amazon is a rainforest in South America. ... Siberia is also an album by Echo & The Bunnymen. ... Jet streams are fast flowing, relatively narrow air currents found in the atmosphere at around 12 km above the surface of the Earth, just under the tropopause. ...

The mechanism of an impact winter is very similar to that theorised would occur after a nuclear war, leading to nuclear winter. Volcanoes also eject large amounts of opaque material into the higher parts of the atmosphere, with large explosions such as the 1991 explosion of Mount Pinatubo having measurable effects on the world's climate. The simultaneous eruption of a number of large volcanoes, a catastrophic volcanic winter scenario, is another proposed mechanism for extinction events. Nuclear War is a card game designed by Douglas Malewicki, and originally published in 1966. ... Nuclear winter is a hypothetical global climate condition that is predicted to be a possible outcome of a large-scale nuclear war. ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... Mount Pinatubo is an active volcano located on the island of Luzon in the Philippines, at the intersection of the borders of the provinces of Zambales, Bataan, and Pampanga. ... A volcanic winter is the reduction in temperature caused by volcanic ash and droplets of sulfuric acid obscuring the sun, usually after a volcanic eruption (hence the name). ...

A large asteroid impacting the Earth's surface at a deep ocean would likely not cause an impact winter, but instead would cause a devastating tsunami. The tsunami that struck Malé in the Maldives on December 26, 2004. ...

An impact winter is not possible for at least 100 years, as there is no known object on a collision course with earth that is large enough to generate one. On March 16, 2880, the asteroid (29075) 1950 DA has a maximum of one in 300 chance of impacting Earth. Such an impact could cause an impact winter. March 16 is the 75th day of the year in the Gregorian Calendar (76th in Leap years). ... (Redirected from 2880) (28th century - 29th century - 30th century - more centuries) The 29th century (Gregorian Calendar) comprises the years 2801-2900. ... Asteroid 1950 DA, radar image (29075) 1950 DA is an asteroid considered to be the near Earth object with the highest known probability of crashing into Earth, according to the Palermo Technical Impact Hazard Scale. ...

Impact winters in popular culture

Impact winter (along with nuclear and volcanic winters) are often the subject of science fiction novels and short stories. 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. ... Daniel Defoes Robinson Crusoe; title page of 1719 newspaper edition A novel (from French nouvelle, new) is an extended fictional narrative in prose. ...

In the episode "Impact Winter" of the popular television show The West Wing, NASA sights a large asteroid that could possibly collide with Earth. President Bartlet recounts the worst case scenario, saying "If the asteroid hits [the forests of Russia], a shower of burning rock rains down on those woods and starts a fire that burns, that shrouds the hemisphere in a blanket of soot and ash that blocks out the sun for weeks. 'Impact Winter', they call it." poo The West Wing is a popular and widely acclaimed American television serial drama created by Aaron Sorkin which is produced and currently co-written by John Wells, Sorkin having left the show at the end of its fourth season. ... This article or section does not cite its references or sources. ...

See also

• Asteroid deflection strategies
• List of noteworthy asteroids
  • 99942 Apophis - a Near Earth Asteroid (NEA)

Artists impression of a major impact event. ... The following is a list of noteworthy asteroids in our Solar system. ... Close approach of Apophis on April 13, 2029 The white bar indicates uncertainty in the range of positions 99942 Apophis (previously better known by its provisional designation 2004 MN4) is a Near-Earth asteroid that caused a brief period of concern in December 2005 because initial observations indicated a relatively...

External links

• Geotimes story on the Chicxulub impact and the possibility of an impact winter
• NASA's Near Earth Object Program