Tunguska explosion in 1908 caused by asteroid grazing Earth
The Tunguska event destroyed 80 million trees in Siberia (and 3 people), yet there was no impact crater. The prevailing theory was that an asteroid or meteor exploded in the atmosphere. Now scientists believe a large asteroid skipped through the atmosphere and bounced back into space. Had the large rock hit, the damage would have been much much worse and perhaps have triggered an extinction level event.
In the early morning of June 30, 1908, a massive explosion flattened entire forests in a remote region of Eastern Siberia along the Tunguska River. Curiously, the explosion left no crater, creating a mystery that has puzzled scientists ever since — what could have caused such a huge blast without leaving any remnants of itself?
Now Daniil Khrennikov at the Siberian Federal University in Russia and colleagues have published a new model of the incident that may finally resolve the mystery. Khrennikov and co say the explosion was caused by an asteroid that grazed the Earth, entering the atmosphere at a shallow angle and then passing out again into space.
Lucky miss
If Khrennikov and colleagues are correct, then Earth had a lucky near-miss that morning. A direct impact with a 656 foot-wide (200 meter-wide) asteroid would have devastated Siberia, leaving a crater 2 miles (3 kilometers) wide. It would also have had catastrophic effects on the biosphere, perhaps ending modern civilization.
In the event, the Tunguska impact is thought to have killed perhaps three people because the region is so remote. It could clearly have been much worse.