What causes the most destruction from a nuclear bomb on earth is the blast wave traveling through the atmosphere. No atmosphere, no blast wave. So the bomb on the surface or nearby would only have the effect of from the light of the fireball. This would just put a fine pottery glaze on a silicate rich asteroid. What you need is for Bruce Willis to drill a hole to the center of the asteroid and seal the shaft before detonation. This would cause the formation of a plasma gas whose pressure would burst the asteroid like cherry bomb in a cantaloupe. Those who have done THAT experiment find that you end up with large chunks instead of small pieces. So you would end trade one large problem for several smaller problems the biggest of which could be half of the original asteroid. We need another plan. DT ____________________________________________________ Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs