Asteroid airburst
The leading scientific explanation for the explosion is the airburst of an asteroid 6–10 kilometres (4–6 miles) above Earth's surface.
Meteoroids enter Earth's atmosphere from outer space every day, travelling at a speed of at least 11 kilometres per second (6.8 mi/s). The heat generated by compression of air in front of the body (ram pressure) as it travels through the atmosphere is immense and most asteroids burn up or explode before they reach the ground. Since the second half of the 20th century, close monitoring of Earth's atmosphere has led to the discovery that such asteroid airbursts occur rather frequently. A stony asteroid of about 10 metres (30 ft) in diameter can produce an explosion of around 20 kilotons, similar to that of the Fat Man bomb dropped on Nagasaki, and data released by the U.S. Air Force's Defense Support Program indicate that such explosions occur high in the upper atmosphere more than once a year. Tunguska-like megaton-range events are much rarer. Eugene Shoemaker estimated that such events occur about once every 300 years.
