From Rick A Harris:

Re: Astronomers catch a “shooting star” (March 25): “Hitting such a fragile asteroid with an atomic bomb, as Bruce Willis did in the 1998 movie Armageddon, would merely turn it in to a deadly swarm of shot gun pellets.” ... is incorrect. Shotgun pellet sized objects hitting our atmosphere at any speed would be harmless. At high speeds, they would burn up quickly. At low speeds they would drop to the surface at a terminal velocity that would harm virtually nothing. A “rain” of shotgun pellet sized stone would be no more harmful than hail, except for planes in flight and the cleanup afterwards!