Torino scale

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.

Contents

1 Overview

2 History

3 Current Torino scale

4 Objects with high Torino ratings

5 External links

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. There are no fractional values or decimal values used.

Torino scale

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 or not a collision will occur. If the encounter is less than a decade away, governmental contigency 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 or not a collision will occur. If the encounter is less than three decades away, governmental contigency planning may be warranted.
7.	A very close encounter by a large object, which if occurring this century, poses an unprecendented but still uncertain threat of a global castastrophe. 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.
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 unprecendented 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] (http://neo.jpl.nasa.gov/torino_scale.html).

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 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 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 started to work on a re-word 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.