Comprehensive Mitigation Plan
Comets and asteroids come in a variety of sizes. In general, smaller impacts occur much more frequently than larger impacts. Large impacts are rare events. It is natural to tailor the mitigation plan to provide a comprehensive coverage for the entire scope of threats. Refer to the Plan of Attack..
At the bottom of the scale are the small impactors that will be burned up in the atmosphere. The smallest objects are the size of a grain of sand that turn into "shooting stars" as they enter the atmosphere. The larger objects up to 100 feet (30 meters) in diameter produce bolides in the upper levels of the atmosphere. It is estimated that 200,000 tons of this small meteoroidal material bombards the Earth each year.23 No action is required for these objects because the impactor is small and will be destroyed by the protective nature of the Earth’s atmosphere.
The next layer up is the asteroids and comets that range in size from approximately 100 feet to 0.6 miles in diameter (30 m – 1.0 km). These impactors will cause local or regional damage. The primary mitigation approach will be to deflect or destroy the impactor. The back-up approach is to evacuate the zone of destruction around the point of impact. The zone of destruction is the area within the 1-psi overburst pressure. For ocean impacts, the zone of destruction also includes the shorelines that will be affected by tsunamis.
The next layer up is the asteroids and comets that range in size from approximately 0.6 miles to 8.0 miles in diameter (1 km – 13 km). These impactors will cause global damage. The KT event that resulted in the extinction of the dinosaurs is estimated as a 8.0 mile diameter asteroid. The primary mitigation approach will be to deflect or destroy the impactor. The back-up approach is to survive the impact in the shelter complex described in this website.
The next layer up is the asteroids and comets for which there is no second line of defense. The objects are so large that "impact" shelters will be ineffective. Our only hope lies in the destruction or deflection of these potential impactors. This layer may range from asteroids approximately 8.0 miles to 12.0 miles in diameter (13 km – 20 km).
The top layer is a true end of world scenario. Comets from the Oort Cloud can range in size up to several hundreds of miles in diameter. They travel at incredible speeds as they approach the Earth. Giant comets and meteors are too large to be destroyed. In general, the best we could hope to accomplish is a partial destruction and dispersion of these fragments, such that only a few fragments would hit the Earth. In this approach, we would make the assumption up front that the Earth would be impacted by one or more large comet fragments. This approach must be coupled with a shelter approach in order to achieve any possibility of survival.