“Planetary defense” is a fig leaf covering the development of technologies to intercept and destroy ballistic missiles above the atmosphere.

The belief is that the first country to have this reliably at scale breaks the “mutually assured destruction” paradigm that has governed nuclear weapons policy for decades. If the U.S. can send nuclear ballistic missiles, but can’t be hit by nuclear missiles, what stops them from just nuking anyone who disagrees with them?

Intercepting a meteor falling to Earth may be not too unlike intercepting a ballistic missile in its terminal descent from high altitude.