The Torino Scale is a method for categorizing the impact hazard associated with 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. Where 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 so large that it is capable of precipitating a global disaster. There are no fractional values or decimal values used.
The sAn object is assigned a 0 to 10 value based on its collision probability and its kinetic energy (expressed in megatons). Note: The Little Boy weapon dropped on Hiroshima had a yield of approximately 13 kilotons. Thus, a megaton 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 near-Earth objects 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 near-Earth objects. ("Torino Scale" is the proper usage, not "Turin Scale.) [ top ]
The Torino Scale also uses a color code from white to yellow to orange to red. Each color code has an overall meaning:
| EVENTS HAVING NO LIKELY CONSEQUENCES | |
| 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. |
| EVENTS MERITING CAREFUL MONITORING | |
| 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. |
| EVENTS MERITING CONCERN | |
| 2. | A somewhat close, but not unusual encounter. Collision is very unlikely. |
| 3. | A close encounter, with 1% or greater chance of a collision capable of causing localized destruction. |
| 4. | A close encounter, with 1% or greater chance of a collision capable of causing regional devastation. |
| THREATENING EVENTS | |
| 5. | A close encounter, with a significant threat of a collision capable of causing regional devastation. |
| 6. | A close encounter, with a significant threat of a collision capable of causing a global catastrophe. |
| 7. | A close encounter, with an extremely significant threat of a collision capable of causing a global catastrophe. |
| CERTAIN COLLISIONS | |
| 8. | A collision capable of causing localized destruction. Such events occur somewhere on Earth between once per 50 years and once per 1000 years. |
| 9. | A collision capable of causing regional devastation. Such events occur between once per 1000 years and once per 100,000 years. |
| 10. | A collision capable of causing a global climatic catastrophe. Such events occur once per 100,000 years, or less often. |
As a result of the 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.
