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.

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).

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:

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 [http://neo.jpl.nasa.gov/news/news146.html 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 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 2008, 1950 DA is one of two objects rated above Level 0 by NEODyS, [cite web
title = NeoDys Risk page
work =
publisher = NEODyS, Hyperborea, Italy
year = 2008
url = http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?riskpage:0;main
doi =
accessdate = 2008-10-08] 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 suggest 2007 VK184 has a probability of 1 in 3130 chance to hit the Earth during June 2048. These figures translate into a 0.032% chance to hit (or 99.968% to miss).Fact|date=May 2008 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.

2008 AF4 is another object on the Torino Scale of 1. It is thought to have a 1 in 909,000 chance of impacting the Earth in 2096, 2099, or 2100.

Due to exaggerated press coverage of asteroids such as mpl|2003 QQ|47, 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.

ee also

*Impact event
*Asteroid deflection strategies
*Palermo scale

References

External links

* [http://neo.jpl.nasa.gov/torino_scale1.html The Torino Impact Hazard Scale]
* [http://impact.arc.nasa.gov/torino.cfm NASA Ames: Asteroid and Comet Impact Hazards: The Torino Scale]
* [http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?riskpage:0;main NEODyS Impact Risk Page] – NEODyS current risk list
* [http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2006XG1;risk NEODyS 2006 XG1 Impactor Table]
* [http://neo.jpl.nasa.gov/risk/ NASA Near Earth Object Program: Impact Risk] – NASA Near Earth Object Program current risk list
* [http://neo.jpl.nasa.gov/images/torino_scale.jpgTorino Scale]
* [http://www.newscientist.com/news/news.jsp?id=ns99994178 "New Scientist:" "Row erupts over asteroid press scare" (18 September 2003)]
* [http://www.torinoscale.com/ The Torino Scale]