NASA admits there's 'a chance' that asteroid 2013 TX68 COULD smash into Earth

[muriel_volestrangler]

25. But it's not many nukes at once

Asteroids with a diameter of 7 meters enter Earth's atmosphere with as much kinetic energy as the atomic bomb dropped on Hiroshima (approximately 16 kilotons of TNT) about every 5 years, but the air burst is reduced to just a third, or about 5 kilotons of TNT.[7] These ordinarily explode in the upper atmosphere, and most or all of the solids are vaporized.[9] Objects with a diameter of roughly 50 m (164 ft) strike Earth approximately once every thousand years,[10] producing explosions comparable to the one known to have detonated roughly 8.5 kilometers (28,000 ft) above Tunguska in 1908.[11]

https://en.wikipedia.org/wiki/Impact_event

In the Wikipedia table, a 98ft diameter asteroid has kinetic energy at atmospheric entry of 1.3MT. They don't calculate the impact energy for one that small (because it would still probably explode in the air, like Tunguska), but extrapolating from the larger ones they do do the calculation for, it would lose well over half its energy - in fact, the airburst would be more damaging (the calculations come from Imperial College, London - a sample one).

It's equivalent to one modest thermonuclear bomb - the kind of thing they tested many times without affecting weather, and that do hit Earth every few hundred years.