The fragmentation of small asteroids in the atmosphere

The effect of the atmosphere on impacting asteroids and comets is investigated. It is found that the atmosphere is inefficient in preventing impact damage to the ground when the radius of a stony asteroid exceeds 100 m and that of a comet exceeds 500 m. For iron meteorites that impact at greater than 20 km/s, the critical radius is about 20-30 m. For low-velocity iron meteorites that hit at 11.2-15 km/s, the critical radius is only 2 m. While the dissipation of energy in the atmosphere protects the ground from impact damage, it can enhance the damage done by the airburst. The area of destruction produced by the airburst during the impact of small asteroids can be up to twice as large as would have been the case had the same energy been released at sea level. The plumes of stony meteorites with radii over about 60 km break out of the atmosphere and float around the earth, carrying entrapped dust whose deposition may provide a counter for large meteorite impacts.