Relative Frequencies and Magnitudes of Bolide Explosions and Impact Events

In light of the destructive bolide explosion over Chelyabinsk in Russia earlier this month, I have reviewed the recent history of meteoric events. From A.D. 1908 to 2013, there have been 11 confirmed events with potential explosive equivalencies greater than or equal to 10 kilotons of TNT. These are summarized below and suggest an observed frequency of such incidents that is somewhat higher than previous conservative predictions.

Eight of the observed explosions or impact events occurred over the greater Eurasian expanse. This continental zone includes just over 10.3 percent of the planet’s surface area. Extrapolating from these data yields an estimate of about seven such intermediate incidents per decade, which is not much lower than the number allegedly observed by military satellites. During the 105-year period bracketed by the Tunguska and Chelyabinsk explosions, there were also at least four bolides that exceeded 100kt equivalencies.

1908	Tunguska Event	15 Mt
1930	Curuçá River bolide explosion	5 Mt
1932	Arroyomolinos de León bolide	190 kt
1947	Sikhote-Alin impact	10 kt
1972	Great Daylight Fireball	80 kt
1993	Lugo bolide explosion	10 kt
1994	Marshall Islands Fireball	11 kt
2002	Eastern Mediterranean Event	20 kt
2004	Antarctic bolide explosion	12 kt
2009	Sulawesi bolide explosion	50 kt
2013	Chelyabinsk bolide explosion	500 kt
2016	South Atlantic fireball	13 kt

The Great Daylight Fireball of 1972 was caused by a near-Earth asteroid that passed harmlessly through the atmosphere over North America at least 35 miles above the surface. Estimates of its potential damage vary wildly, but I have selected a number in the upper range. Given the speed and luminosity of the bolide, had it grazed the planet at a more acute angle, I expect that the results would have been spectacular and potentially devastating.

As the Chelyabinsk explosion has proven, these intermediate objects present a very real danger. They are smaller, harder to detect, and much more common than the potential doomsday asteroids we can spot now. And we still lack the infrastructure to stop either of these threats.

Updated to include the South Atlantic fireball of 2016, which exploded several hundred miles southeast of Brazil (http://neo.jpl.nasa.gov/fireballs/).