BEWARE the blast from above: small asteroids that explode before they hit the ground may be more dangerous than we thought.
Asteroids a few tens of metres in diameter rip through the atmosphere at between 40 and 60 times the speed of sound, and many explode before they hit Earth. Extreme friction and heating can cause these asteroids to flatten into pancakes, which increases drag even more and eventually tears them apart. The resultant “airburst” is thought to be behind the 1908 Tunguska explosion in Siberia, which levelled 2000 square kilometres of forest.
Because airbursts spread material over a wide…
