It appears that the human population is at more at risk from smaller rather than larger Earth impacting asteroids.During the past 20 years more than 550 small asteroids ranging in size from 3 to 60 feet in diameter have entered the Earth's atmosphere. They had impact energies ranging from 5 to 500,000 tons of TNT. Newly released data show that most of them exploded high above the ground doing little or no damage at the surface.