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 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 2. A somewhat close, but not unusual encounter.
Collision is very unlikely.
Threatening events 5. A close encounter, with a significant threat of a collision capable of causing regional devastation. A close encounter, with a significant threat of a collision capable of causing a global catastrophe. A close encounter, with an extremely significant threat of a collision capable of causing a global catastrophe. Certain collisions 8.