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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.

Overview

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. Only integer values are ever 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.

History

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.") In 2005 a re-worded scale was published to better communicate the risks to the public.

Current Torino Scale

The Torino Scale also uses a color code scale: white, green, yellow, orange, red. Each color code has an overall meaning:

NO HAZARD (white)
0.	The likelihood of a collision is zero, or is so low as to be effectively zero. Also applies to small objects such as meteors and bodies that burn up in the atmosphere as well as infrequent meteorite falls that rarely cause damage.
NORMAL (green)
1.	A routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to re-assignment to Level 0.
MERITING ATTENTION BY ASTRONOMERS (yellow)
2.	A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0.
3.	A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localized destruction. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.
4.	A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of regional devastation. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.
THREATENING (orange)
5.	A close encounter posing a serious, but still uncertain threat of regional devastation. Critical attention by astronomers is needed to determine conclusively whether a collision will occur. If the encounter is less than a decade away, governmental contingency planning may be warranted.
6.	A close encounter by a large object posing a serious but still uncertain threat of a global catastrophe. Critical attention by astronomers is needed to determine conclusively whether a collision will occur. If the encounter is less than three decades away, governmental contingency planning may be warranted.
7.	A very close encounter by a large object, which if occurring this century, poses an unprecedented but still uncertain threat of a global catastrophe. For such a threat in this century, international contingency planning is warranted, especially to determine urgently and conclusively whether a collision will occur.
CERTAIN COLLISIONS (red)
8.	A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offshore. Such events occur on average between once per 50 years and once per several 1000 years.
9.	A collision is certain, capable of causing unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact. Such events occur on average between once per 10,000 years and once per 100,000 years.
10.	A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often.

Wording taken from [1].

Objects with high Torino ratings

The current record for highest Torino rating is held by 99942 Apophis, a 400m near-Earth asteroid, which was later downgraded to 0. On December 23, 2004, NASA's Near Earth Object Program Office announced that Apophis (then known only by its provisional designation 2004 MN₄) was the 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 Friday, April 13, 2029 quite closely but with no possibility of an impact. Future uncertainties in the orbit of Apophis will occur because of gravitational deflection during the 2029 encounter, so a Torino rating of 1 (for an encounter in 2036) applied until August 2006, when Apophis was downgraded to 0.

Prior to Apophis, no NEO had ever been given a Torino Scale value higher than 1. In February 2006, the rating for 2004 VD17 was upgraded to a value of 2 due to a possible encounter in the year 2102, making it the second asteroid to ever be given a Torino Scale value higher than 1. Additional observations of 2004 VD17 resulted in a downgrade to 0.

As of February 2007, 1950 DA is one of two objects rated above Level 0 by NEODyS; it is rated Level 1. It, however, is not listed by the Sentry program because its risk is not within 100 years.

2007 VK184 is the second object, an asteroid, which is listed on the Near Earth Object Risk List with a Torino Scale of Level 1. The object was discovered on November 12, 2007, by the Catalina Sky Survey.

According to the Near Earth Object-list, 95 observations over 35 days suggests 2008 AF4 has a probability of 1 in 3130 chance to hit the Earth during June 2048. Those figures translates into a 0.032% chance to hit (or 99.968% to miss). The asteroid is estimated to have a diameter of 130 meters, and travels through space with a speed of 15.63 km/s relative to the Earth.

Due to exaggerated press coverage of asteroids such as 2003 QQ47, astronomers started to work on a re-wording of the Torino Scale, which was published in 2005. It was also considered to phase it out completely in favour of a scale which is less likely to generate false alarms that may reduce public confidence in genuine alerts. One alternative would be the Palermo Technical Impact Hazard Scale.

Asteroids with listing above 1 on the Torino Scale are rare and are, according to NEO, often downgraded to Level 0 after the initial observations.

References

External links

The Torino Impact Hazard Scale
NASA Ames: Asteroid and Comet Impact Hazards: The Torino Scale
NEODyS Impact Risk Page – NEODyS current risk list
NEODyS 2006 XG1 Impactor Table
NASA Near Earth Object Program: Impact Risk – NASA Near Earth Object Program current risk list
Torino Scale
New Scientist: "Row erupts over asteroid press scare" (18 September 2003)
The Torino Scale

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 ==Objects with high Torino ratings==<!-- This section is linked from [[Apep]] -->
-{{contradict-other|2007 VK184|there|date=May 2008}}
 The current record for highest Torino rating is held by [[99942 Apophis]], a 400[[metre|m]] [[near-Earth asteroid]], which was later downgraded to 0. On [[December 23]], [[2004]], NASA's Near Earth Object Program Office [http://neo.jpl.nasa.gov/news/news146.html announced] that Apophis (then known only by its [[provisional designation]] 2004 MN<sub>4</sub>) was the 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 Friday, [[April 13]], [[2029]] quite closely but with no possibility of an impact. Future uncertainties in the orbit of Apophis will occur because of gravitational deflection during the 2029 encounter, so a Torino rating of 1 (for an encounter in [[2036]]) applied until August 2006, when Apophis was downgraded to 0.
 Prior to Apophis, no NEO had ever been given a Torino Scale value higher than 1. In February 2006, the rating for {{mpl|2004 VD|17}} was upgraded to a value of 2 due to a possible encounter in the year [[2102]], making it the second asteroid to ever be given a Torino Scale value higher than 1. Additional observations of {{mpl|2004 VD|17}} resulted in a downgrade to 0.
-[[As of February 2007]], [[1950 DA]] is one of three objects rated above Level 0 by [[NEODyS]]; it is rated Level 1. It is the only known asteroid whose hazard could be above the background level ([[Palermo Technical Impact Hazard Scale|Palermo Technical Impact Scale]] value = +0.17). By comparison, the threat from {{mpl|2006 XG|1}}, which was previously rated Level 1 before being downgraded to 0, is less than one-tenth the background level.
+[[As of February 2007]], [[1950 DA]] is one of  objects rated above Level 0 by [[NEODyS]]; it is rated Level 1. It, ,           is    .
 [[2007 VK184]] is the second object, an asteroid, which is listed on the Near Earth Object Risk List with a Torino Scale of Level 1. The object was discovered on [[November 12]], [[2007]], by the Catalina Sky Survey.
-[[2008 AF4]] is the third object, which also is listed on the Torino Scale as 1. Its mostly likely encounter with [[Earth]] will be on [[09 January]], [[2089]].
 According to the Near Earth Object-list, 95 observations over 35 days suggests 2008 AF4 has a probability of 1 in 3130 chance to hit the Earth during June 2048. Those figures translates into a 0.032% chance to hit (or 99.968% to miss). The asteroid is estimated to have a diameter of 130 meters, and travels through space with a speed of 15.63 km/s relative to the Earth.