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 communication 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 an integer 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 Earth's atmosphere intact. A 10 indicates that a collision is certain, and the impacting object is large enough to precipitate a global disaster.
An object is assigned a 0 to 10 value based on its collision probability and the kinetic energy (expressed in megatons of TNT) of the possible collision.
The Torino Scale is defined only for potential impacts less than 100 years in the future.
"For an object with multiple potential collisions on a set of dates, a Torino Scale value should be determined for each date. It may be convenient to summarize such an object by the greatest Torino Scale value within the set."
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.")
Due to exaggerated press coverage of Level 1 asteroids, a rewording of the Torino Scale was published in 2005, adding more details and renaming the categories: in particular, Level 1 was changed from "Events meriting careful monitoring" to "Normal".
The Torino Scale has served as the model for the Rio Scale which quantifies the validity and societal impact of SETI data.
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.|
|1||A routine discovery in which a pass near 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 reassignment 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 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 reassignment 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 reassignment 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 reassignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.|
|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 thousand years, but with usually none or only a few deaths and with fast recovery and a low/moderate amount on damage depending on the area.|
|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, an asteroid like that could cause a few thousand deaths and cost millions/billions of damage depending on the area and serious damage to the environment.|
|10||A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization and wildlife as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often.|
No incoming object has ever been rated above level 4, though over all Earth's history impacts have spanned the full range of damage described by the scale.
The Chicxulub impact, believed by most scientists to be a significant factor in the extinction of the non-avian dinosaurs, has been estimated at 100 million (108) megatons, or Torino Scale 10. The impacts which created the Barringer Crater and the 1908 Tunguska event are both estimated to be in the 3–10 megaton range,corresponding to Torino Scale 8. The 2013 Chelyabinsk meteor had a total kinetic energy prior to impact of about 0.5 megatons, corresponding to Torino Scale 0. Between 2000 and 2013, 26 asteroid impacts with an energy of 1–600 kilotons were detected.
The biggest hydrogen bomb ever exploded, the Tsar Bomba, was around 50 megatons. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.
The comet C/2013 A1, which passed close to Mars in 2014, was originally estimated to have a potential impact energy of 5 million to 24 billion megatons, and in March 2013 was estimated to have a Mars impact probability of ~1:1250, corresponding to the Martian equivalent of Torino Scale 6.The impact probability was reduced to ~1:120000 in April 2013, corresponding to Torino Scale 1 or 2.
This is a partial list of near-Earth asteroids that have been listed with a Torino Scale rating of 1+ and been lowered to 0 or been removed from the Sentry Risk Table altogether. Most objects that reach a Torino Scale of 1 have a short observation arc of less than 2 weeks and are quickly removed as the observation arc gets longer and more accurate.
(89959) 2002 NT7 (prov. designation:2002 NT7) is a near-Earth object with a diameter of 1.4 kilometers and potentially hazardous asteroid of the Apollo group. It has a well determined orbit with an observation arc of 64 years including precovery images by Palomar Observatory dating back to 1954.
(143649) 2003 QQ47, provisional designation 2003 QQ47, is a kilometer-sized asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group which became briefly notable upon its discovery in late August 2003 when media outlets played up a very preliminary report that it had a 1 in 250,000 chance of impacting into Earth on 21 March 2014.
Sentry is a highly automated impact prediction system operated by the JPL Center for NEO Studies (CNEOS) since 2002. It continually monitors the most current asteroid catalog for possibilities of future impact with Earth over the next 100+ years. Whenever a potential impact is detected it will be analyzed and the results immediately published by the Near Earth Object Program. However, several weeks of optical data are not enough to conclusively identify an impact years in the future. By contrast, eliminating an entry on the risk page is a negative prediction; a prediction of where it will not be. Scientists warn against worrying about the possibility of impact with an object based on only a few weeks of optical data that show a possible Earth encounter years from now. Sometimes, it cannot even be said for certain what side of the Sun such an object will be at the time of the listed virtual impactor date. For example, even though 2005 ED224 has a 1-in-500,000 chance of impacting Earth on 11 March 2023, it is expected to be farther than the Sun at the time. Most objects on the Sentry Risk Table have an observation arc of less than 14 days and have not been observed for years.
(144898) 2004 VD17, provisional designation 2004 VD17, is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group once thought to have a low probability of impacting Earth on 4 May 2102.
2007 VK184 is a sub-kilometer asteroid, classified as a near-Earth object of the Apollo group, and estimated to be approximately 130 meters (430 ft) in diameter. It was listed on the Sentry Risk Table with a Torino Scale rating of 1. A Torino scale rating of 1 is a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.
(367789) 2011 AG5, provisional designation 2011 AG5, is a sub-kilometer asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It has a diameter of about 140 meters (460 ft). It was removed from the Sentry Risk Table on 21 December 2012 and as such it now has a rating of 0 on the Torino Scale.
2010 AU118 (also written 2010 AU118) is a potential Amor near-Earth asteroid with an observation arc of only 1.4 days and thus a poorly determined orbit. It was announced on 27 May 2010 based on images taken by the Wide-field Infrared Survey Explorer (WISE) on 13–15 January 2010. It was removed from the Sentry Risk Table on 14 June 2014 as a result of an update to the Sentry software. Another software update restored it to the Sentry Risk Table in 2017. It was again removed from the sentry list on 3 October 2018.
(410777) 2009 FD is a carbonaceous sub-kilometer asteroid and binary system, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, discovered on 24 February 2009 by astronomers of the Spacewatch program at Kitt Peak National Observatory near Tucson, Arizona, in the United States.
2012 KP24 (also written 2012 KP24) is a near-Earth asteroid and fast rotator with an observation arc of only 5 days and has a modestly determined orbit for an object of its size.
2013 TV135 is an Apollo near-Earth asteroid estimated to have a diameter of 450 meters (1,480 ft). On 16 September 2013, it passed about 0.0448 AU (6,700,000 km; 4,160,000 mi) from Earth. On 20 September 2013, it came to perihelion (closest approach to the Sun). The asteroid was discovered on 12 October 2013 by Ukrainian amateur astronomer Gennadiy Borisov with a custom 0.2-meter (7.9 in) telescope using images dating back to 8 October 2013. It was rated level 1 on the Torino Scale from 16 October 2013 until JPL solution 26 on 3 November 2013. It was removed from the JPL Sentry Risk Table on 8 November 2013 using JPL solution 32 with an observation arc of 27 days.
2014 OO6 (also written 2014 OO6) is an Apollo near-Earth asteroid discovered in 2014 and was the most dangerous one discovered in 2014 that remained on the Sentry Risk Table as of early December 2014. The asteroid is estimated to be roughly 75 meters (246 ft) in diameter and had a 1 in 83,000 chance of impacting Earth on 11 January 2051. However, the nominal best-fit orbit shows that 2014 OO6 will be 1.5 AU (220,000,000 km; 140,000,000 mi) from Earth on 11 January 2051.
2007 VE191 is a sub-kilometer asteroid, classified as near-Earth asteroid of the Apollo group that was listed on the Sentry Risk Table.
2014 XL7 (also written 2014 XL7) was the most dangerous potentially hazardous asteroid discovered in 2014 that remained on the Sentry Risk Table at the end of 2014. The Apollo near-Earth asteroid is estimated to be roughly 230 meters in diameter and had a cumulative 1 in 83000 chance of impacting Earth on 4–5 June between the years 2048 and 2084. It was removed from the Sentry Risk Table on 15 January 2015 using JPL solution 9 with an observation arc of 35 days.
2016 EU85 is an asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 400 meters in diameter. It was first observed on 10 March 2016, by the Pan-STARRS survey at Haleakala Observatory, Hawaii, United States.
2017 XO2, also written 2017 XO2, is a sub-kilometer asteroid and near-Earth object of the Apollo group approximately 110 meters (360 feet) in diameter. The asteroid was discovered by Pan-STARRS in December 2017, after it already had approached Earth at 0.051 AU (7,600,000 km) or 20 lunar distances (LD) on 6 November 2017. On 26 April 2057, it will pass Earth at a similar distance of 21 LD again.
2018 XB4 (also written 2018 XB4) is an Apollo near-Earth asteroid roughly 53 meters (170 feet) in diameter. It was discovered on 13 December 2018 when the asteroid was about 0.125 AU (18,700,000 km; 11,600,000 mi) from Earth and had a solar elongation of 146°. It passed closest approach to Earth on 1 January 2019. Of the asteroids discovered in 2018, it had the highest Palermo scale rating at –3.6. In mid-2019 it was recovered which extended the observation arc to 177 days and was removed from the Sentry Risk Table on 12 June 2019. It is now known that on 22 June 2092 the asteroid will pass about 0.033±0.015 AU from Earth.
2018 VP1 is an Apollo near-Earth asteroid roughly 2 meters (7 feet) in diameter. The asteroid had a 0.41% chance (1 in 240) of impacting Earth on 2 November 2020 01:12 UT. It was discovered on 3 November 2018 when it was about 0.003 AU (450,000 km; 280,000 mi) from Earth and had a solar elongation of 165 degrees. The asteroid has a short 12.9 day observation arc. It was last observed on 16 November 2018 by the European Southern Observatory Very Large Telescope at apparent magnitude 26 pushing the telescope close to the limiting magnitude.
1979 XB is a lost asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It has a short observation arc of 3.9 days and is roughly estimated to be 660 meters in diameter. The unnumbered minor planet has a poorly constrained orbit and has not been observed in 40 years. It has been listed on the Sentry Risk Table since the list started in 2002. With a cumulative Palermo Technical Impact Hazard Scale of -2.79, the poorly known orbit and assumed size place 1979 XB third on an unconstrained listing of the Sentry Risk Table.
2020 VV is an Apollo near-Earth asteroid roughly 12 meters in diameter. According to the Sentry monitoring system, the asteroid has a 1 in 1.5 million chance of impacting Earth on 12 October 2033 11:43 UT. The asteroid has a modest 61 day observation arc. The nominal Earth approach is on 18 October 2033 at a distance of 0.01 AU, but the line of variations (LOV) is only known with an accuracy of ±2 days. The line of variations allows the asteroid to impact Earth or pass as far away as 0.02 AU. With a diameter range of 10–22 meters the asteroid could be as large as the Chelyabinsk meteor.
2020 XR is an Apollo near-Earth object and potentially hazardous asteroid roughly 390 meters in diameter. With a 5-day observation arc it was briefly listed as having a 1 in 11,000 chance of impacting Earth on 1 December 2028 placing it at the top of the Sentry Risk Table with a Palermo scale rating of -0.70.
This article incorporates public domain material from websites or documents ofthe National Aeronautics and Space Administration .