Tunguska

A hundred years ago today, something crashed into the forest of Siberia. Or not-- at least one scientist argues a huge natural gas explosion did the deed. Uncertainty has always surrounded the Tunguska Event, which leveled a huge expanse of forest and brightened the night sky as far away as London. The fact that the incident site was off-limits to Western science for decades during the Soviet period clearly fueled the mystery.

The consensus today is that a small asteroid exploded deep into Earth's atmosphere that day. Latest estimates are that the explosiom may not have been quite as powerful as first thought, and that the body was smaller, perhaps only 56 feet in diameter. Some scientists argue it was a comet, not an asteroid. (Other scientists would say there's likely no difference between asteroids and comets stripped of their volatiles.)

Whatever caused the destruction at Tunguska, it's likely a reminder that Earth has been struck by objects from space in the past, and, barring intervention, will be again. A Tunguska level event could destroy a major city.. A bigger body could reach the ground and be even more catastrophic. There are a few small prohects around the world looking for potentially dangerous objjects in space, but, so far, finding them and creating ways to deflect them away from Earth has not been a priority. That's gambling with the future of humanity. It's a bet we may well win, but we should understand that's what inattention in this area is doing.