Impact winter

Source: Wikipedia, the free encyclopedia.
dinosaurs and many other species on Earth. The impact spewed hundreds of billions of tons of sulfur into the atmosphere, producing a worldwide blackout and freezing temperatures which persisted for at least a decade.[1]

An impact winter is a hypothesized period of

mass extinction, wiping out many of the world's existing species. The Cretaceous–Paleogene extinction event probably involved an impact winter, and led to mass extinction of most tetrapods weighing more than 25 kilograms (55 pounds).[5]

Possibility of impact

Each year, the Earth is hit by 5 m (16 ft) diameter

Asteroid 1950 DA, currently has a 0.005% chance of colliding with Earth in the year 2880,[7] though when first discovered the probability was 0.3%.[6]
The probability goes down as orbits are refined with additional measurements.

Over 300 short-period

comets pass near larger planets, such as Saturn and Jupiter, which can change the comets' trajectories and could potentially put them into an Earth-crossing orbit. This could happen for long-period comets also but the chance is highest for short-period comets. The chance of these directly impacting Earth is far lower than a near-Earth object (NEO) impact. Victor Clube and Bill Napier support a controversial theory that a short-period comet in an Earth-crossing orbit does not need to impact to be hazardous, as it could disintegrate and cause a dust veil with possibilities of a "nuclear winter" scenario with long-term global cooling lasting for thousands of years (which they consider to be similar in probability to a 1 km impact).[8][9][10][11]

Necessary impact factors

The Earth experiences a never-ending barrage of cosmic debris. Small particles burn up as they enter the

extinction-level event or even cause any real harm. Objects release most of their kinetic energy in the atmosphere and will explode if they experience a column of atmosphere greater than or equal to their mass.[2] Extinction-level impacts on the Earth occur about every 100 million years.[3][4][12] Although extinction events happen very rarely, large projectiles can do severe damage.[2][12]
This section will discuss the nature of the hazards posed by projectiles as a function of their size and composition.

Size

A large

meteor, or comet would remain intact through the atmosphere by virtue of its sheer mass. However, an object smaller than 3 km (1.9 mi) would have to have a strong iron composition to breach the lower atmosphere - the troposphere or the lower levels of the stratosphere.[2]

Composition

There are three different composition types for an asteroid or comet:

low-density silicates, organics, ice, volatile and often burn up in the upper atmosphere because of their low bulk density (≤1 g/cm3 (60 lb/cu ft)).[2]

Possible mechanisms

Although the

firestorms
.

Mass ejection of regolith

particulate matter
.

In a study conducted by Curt Covey et al., it was found that an

Toba eruption
.

These pulverized rock particles would remain in the

sun's radiation might not reach the surface.[why?] After the first 20 days, the land temperature might drop quickly, by about 13 °C. After about a year, the temperature could rebound by about 6 °C, but by this time about one-third of the Northern Hemisphere might be covered in ice.[3]

However, this effect could be largely mitigated, even reversed, by a release of enormous quantities of water vapor and carbon dioxide caused by the initial global heat pulse after the impact. If the asteroid hit an ocean (which would be the case with the majority of impact events), water vapor would form the majority of any ejected matter, and would likely result in a major greenhouse effect and a net increase in temperature.[citation needed]

If the impact event is sufficiently energetic it might cause mantle plume (volcanism) at the antipodal point (the opposite side of the world).[15] This volcanism could alone therefore create a volcanic winter, irrespective of the other impact effects.

Multiple firestorms

In combination with the initial debris ejected into the

fire storms, possibly with a global reach into every dense and therefore firestorm-prone forest. These wood fires might release enough amounts of water vapor, ash, soot, tar and carbon dioxide into the atmosphere to perturb the climate on their own and cause the pulverized rock dust cloud blocking the sun to last longer. Alternatively it could cause it to last for a much shorter time, as there would be more water vapor for the rocky aerosol particles to form cloud condensation nuclei. If it causes the dust cloud to last longer, it would prolong the Earth's cooling time, possibly causing thicker ice sheets to form.[3][14]

Past events

In 2016, a scientific drilling project drilled deep into the

rock core samples from the impact itself. This crater is one of the best known impact craters and was the impact responsible for the extinction of the non-avian dinosaurs
.

The discoveries were widely seen as confirming current theories related to both the crater impact and its effects. They confirmed that the rock comprising the peak ring had been subjected to immense pressures and forces, and had been melted by immense heat and shocked by immense pressure from its usual state into its present form in just minutes. The fact that the peak ring was made of granite was also significant, since granite is not a rock found in sea-floor deposits – it originates much deeper in the earth and had been ejected to the surface by the immense pressures of impact. Gypsum, a sulfate-containing rock that is usually present in the shallow seabed of the region, had been almost entirely removed and must therefore have been almost entirely vaporized and entered the atmosphere, and that the event was immediately followed by a huge megatsunami (a massive movement of sea waters) sufficient to lay down the largest known layer of sand separated by grain size directly above the peak ring.

These strongly support the hypothesis that the impactor was large enough to create a 120-mile peak ring, eject molten granite from deep within the earth, create colossal water movements, and eject an immense quantity of vaporized rock and sulfates into the atmosphere, where they would have persisted for a long time. This global dispersion of dust and sulfates would have led to a sudden and catastrophic effect on the climate worldwide by causing large temperature drops, devastating the food chain.[16][17]

Impact on humans

genetic bottleneck in humans.[18]

An impact winter would have a devastating effect on humans, as well as the other species on Earth. With the

economic crisis for the survivors.[19]
These factors would make life on Earth, for humans, extremely difficult.

Agriculture

With the

canned food and grain stockpiles in these countries. However, if the impactor was similar in size to the K/T boundary impactor, agricultural losses might not be compensated with imports to the northern hemisphere from the southern hemisphere or vice versa.[6][19] The only way to keep from starving would be for each country to amass at least a year's worth of food for their people. Not many countries have this; the world's average cereal stock levels are only about 30% of the yearly production.[6][20]

Economics

The cost to clean up after an asteroid or comet impact would cost billions to trillions of dollars, depending on the location impacted.[19][20] An impact in New York City (the 16th most populated city in the world) could cost billions of dollars in financial losses and it could take years for the financial sector (i.e. stock market) to recover.[19] However, the probability of such a naturally specifically aimed impact would be exceedingly low.

Survivability

As of February 20, 2018, there are 17,841 near-Earth objects known. 8,059 potentially hazardous objects are known; they are larger than 140 m (460 ft) and may approach the Earth closer than 20 times the distance to the Moon.[6] 888 NEAs larger than 1 km have been discovered,[21] or 96.5% of an estimated total of about 920.[22]

See also

References

  1. ^ Osterloff, Emily (2018). "How an asteroid ended the age of the dinosaurs". London: Natural History Museum. Archived from the original on 26 April 2022. Retrieved 18 May 2022.
  2. ^
    S2CID 4305299
  3. ^
  4. ^
  5. .
  6. ^
  7. ^ "Sentry Risk Table". NASA/JPL Near-Earth Object Program Office. 9 December 2014. Archived from the original on December 31, 2014. Retrieved 2014-12-10.
  8. Science Daily
    . 1 April 2010. Retrieved 5 November 2014.
  9. ^ Roach, John (7 April 2010). "Comet "Shower" Killed Ice Age Mammals?". National Geographic. Archived from the original on April 10, 2010. Retrieved 5 November 2014.
  10. ^ Hecht, John (2 April 2010). "Did a comet swarm strike America 13,000 years ago?". New Scientist. Retrieved 5 November 2014.
  11. .
  12. ^
  13. .
  14. ^
  15. .
  16. ^ "Updated: Drilling of dinosaur-killing impact crater explains buried circular hills". 2016-05-03.
  17. ^ Fleur, Nicholas St (2016-11-17). "Drilling into the Chicxulub Crater, Ground Zero of the Dinosaur Extinction". The New York Times.
  18. ^ Michael R. Rampino, Stanley H. Ambrose, 2000. "Volcanic winter in the Garden of Eden: The Toba supereruption and the late Pleistocene human population crash", Volcanic Hazards and Disasters in Human Antiquity, Floyd W. McCoy, Grant Heiken
  19. ^
  20. ^
  21. ^ "Discovery Statistics – Cumulative Totals". NASA/JPL CNEOS. February 5, 2018. Retrieved 2018-02-08.
  22. ^ Matt Williams (October 20, 2017). "Good News Everyone! There are Fewer Deadly Undiscovered Asteroids than we Thought". Universe Today. Retrieved 2017-11-14.

External links