Last Updated
Jan 17, 2000
The Newly Adopted Torino Impact Hazard Scale Assessing Asteroid And Comet Impact Hazard Predictions In The 21st Century Near Earth Objects Scale Helps Risk Communication (NASA - July 22, 1999)
Dealing With the Impact Hazard: An International Project (IAU - July 22, 1999)
Torino Impact Scale Created To Assess Earth-Asteroid Close Appro aches (MIT - July 22, 1999)
The Torino Scale (Ames Research Center - July 22, 1999)
New Torino Scale Measures Asteroid Threat (explorezone.com - July 22, 1999) Events Having No Likely Consequences
(White Zone) 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
(Green Zone) 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
(Yellow Zone) 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
(Orange Zone) 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
(Red Zone) 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. Questions/Comments | Mailing List | Credits Ron Baalke, Near-Earth Object Webmaster
Jet Propulsion Laboratory
Pasadena, California
NASA's Near Earch Object Program Office has recently announced that the asteroid named 2004 MN4, discovered last June, has the highest risk of earth impact to date. In the December 23 annoncement, NASA advised that the 400-meter wide asteroid has a 1 in 300 chance of colliding with earth.  As scientists gather more data on 2004 MN4, the probability of collision with earth is expected to decrease.

The level of impact risk is measured in terms of Torino Impact Hazard Scale, and the MN4's score was initially 2 out of 10. 2004 MN4 is expected to come closest to the Earth on April 14, 2029.