Torino level Category Description
0 No hazard (white zone) Zero likelihood of a collision
1 Normal (green zone) Routine discovery in which a pass near the Earth is predicted, but the chance of collision is extremely unlikely
2 Meriting attention by astronomers (yellow zone) Discovery of an object making a close but not highly unusual pass near the Earth, with an actual collision very unlikely
3 Close encounter, with a 1% or greater chance of collision capable of localized destruction
4 Close encounter, with a 1% or greater chance of collision capable of regional devastation
5 Threatening (orange zone) Close encounter that poses a serious but still uncertain threat of regional devastation
6 Close encounter by a large object which poses a serious but still uncertain threat of global catastrophe
7 Very close encounter by a large object, which (if occurring within 100 years) poses an unprecedented but still uncertain threat of a global catastrophe
8 Certain collisions (red zone) Collision is certain, capable of causing localized destruction
9 Collision is certain, capable of causing unprecedented regional devastation
10 Collision is certain, capable of causing global climatic catastrophe
From A Dictionary of Environment and Conservation in Oxford Reference.
Subjects: Environmental Science.