• Nuclear explosions are the only current, practical means for dealing with large objects (comets or asteroids with diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail.

“Although all of these methods are conceptually valid, none is now ready to implement on short notice, the report says. Civil defense and kinetic impactors are probably the closest to readiness, but even these require additional study prior to reliance on them,” the report stated.

NASA has been increasing its ability to track dangerous comets and asteroids. For example, part of the space agency’s recently launched Wide-field Infrared Survey Explorer spacecraft to uncover objects never seen before, including the coolest stars, the universe's most luminous galaxies and some of the darkest near-Earth asteroids and comets.

In addition, NASA's Jet Propulsion Laboratory recently launched the Asteroid Watch Web site to act as a centralized source for information on objects hurtling at Earth.