Information provided through such study is vital to determining the best option for mitigation, which currently include destruction or deflection through detonation of a missile or nuclear device, or vaporization. Besides the threat they represent, these objects also present great opportunity. The same objects that come near the Earth provide the raw materials for large scale space industry. The metal ones are almost pure iron and nickel, but also contain high abundance of such rare metals as platinum and gold. As humans move out into space, asteroids can actually be a resource.
Comets contain lots of water.
Many contain complex hydrocarbons from which rocket fuel and even space habitats may be constructed. Both robotic and human missions to these objects could be the next step in solar system expansion. Major asteroid impacts are a threat to our planet and the human race. They are infrequent, but potentially very destructive. They are a threat primarily because we still do not know how many are in a position to cross Earth's orbit.