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The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets.
It is intended as a tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value. The Palermo Technical Impact Hazard Scale is a similar, but more complex scale.
The Torino Scale uses a scale from 0 to 10. A 0 indicates an object has a negligibly small chance of collision with the Earth, compared with the usual "background noise" of collision events, or is too small to penetrate the Earth's atmosphere intact. A 10 indicates that a collision is certain, and the impacting object is large enough to precipitate a global disaster. There are no fractional values or decimal values used.
An object is assigned a 0 to 10 value based on its collision probability and its kinetic energy (expressed in megatons of TNT). Note: The Little Boy weapon dropped on Hiroshima had a yield of approximately 13 kilotons of TNT. Thus, a megaton of TNT is equivalent to roughly 77 Hiroshima bombs.
The Torino Scale was created by Professor Richard P. Binzel in the Department of Earth, Atmospheric, and Planetary Sciences, at the Massachusetts Institute of Technology (MIT). The first version, called "A Near-Earth Object Hazard Index", was presented at a United Nations conference in 1995 and was published by Binzel in the subsequent conference proceedings (Annals of the New York Academy of Sciences, volume 822, 1997.)
A revised version of the "Hazard Index" was presented at a June 1999 international conference on NEOs held in Torino (Turin), Italy. The conference participants voted to adopt the revised version, where the bestowed name "Torino Scale" recognizes the spirit of international cooperation displayed at that conference toward research efforts to understand the hazards posed by NEOs. ("Torino Scale" is the proper usage, not "Turin Scale.")
The Torino Scale also uses a color code scale: white, green, yellow, orange, red. Each color code has an overall meaning:
| EVENTS HAVING NO LIKELY CONSEQUENCES (white)
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| 0. | The likelihood of a collision is zero, or well below the chance that a random object of the same size will strike the Earth within the next few decades. This designation also applies to any small object that, in the event of a collision, is unlikely to reach the Earth's surface intact.
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| EVENTS MERITING CAREFUL MONITORING (green)
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| 1. | The chance of collision is extremely unlikely, about the same as a random object of the same size striking the Earth within the next few decades.
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| EVENTS MERITING CONCERN (yellow)
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| 2. | A somewhat close, but not unusual encounter. Collision is very unlikely. While meriting attention by astronomers, there is no cause for public attention or public concern. New observations will very likely lead to re-assignment to level 0.
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| 3. | A close encounter, with 1% or greater chance of a collision capable of causing localized destruction. Most likely, new observations will lead to re-assignment to level 0. Attention by the public and public officials merited if the encounter is less than a decade away.
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| 4. | A close encounter, with 1% or greater chance of a collision capable of causing regional devastation. Most likely, new observations will lead to re-assignment to level 0. Attention by the public and public officials merited if the encounter is less than a decade away.
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| THREATENING EVENTS (orange)
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| 5. | A close encounter, with a significant threat of a collision capable of causing regional devastation. If the encounter is less than a decade away, governmental contingency planning may be warranted.
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| 6. | A close encounter, with a significant threat of a collision capable of causing a global catastrophe. If the encounter is less than three decades away, governmental contingency planning may be warranted.
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| 7. | A close encounter, with an extremely significant threat of a collision capable of causing a global catastrophe. For such a threat in this century, international contingency planning is warranted, especially to determine urgently and conclusively whether or not a collision will occur.
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| CERTAIN COLLISIONS (red)
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| 8. | A collision capable of causing localized destruction. Such events occur somewhere on Earth between once per 50 years and once per several 1000 years.
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| 9. | A collision capable of causing regional devastation. Such events occur between once in 10,000 to 100,000 years.
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| 10. | A collision is certain, and will cause global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Events occur on average once per +100,000 years.
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Objects with high Torino ratings
The current record for highest Torino rating is held by 2004 MN4, a 400-meter Near-Earth Asteroid (NEA) which no longer poses an impact risk in the near future.
On December 23 2004, NASA's Near Earth Object Program Office announced (http://neo.jpl.nasa.gov/news/news146.html)
that it was first object to reach a level 2 on the Torino Scale, and it was subsequently upgraded to level 4. It is now expected to pass the Earth on April 13, 2029 without major incident. Uncertainties in the orbit of 2004 MN4 will occur because of the proximity to the earth on April 13, 2029, and the orbit of the asteroid must be evaluated after it passes very near the earth.
Prior to 2004 MN4 no NEO had ever been given a Torino value higher than 1. As of the end of 2004, the highest rated objects are three objects with Torino ratings of one:
Due to exaggerated press coverage of asteroids such as 2003 QQ47, astronomers are now planning to re-word the Torino scale, or to phase it out completely in favour of a scale which is less likely to generate false alarms which may reduce public confidence in genuine alerts. One alternative is the Palermo Technical Impact Hazard Scale.
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