Today is Asteroid Day in remembrance of the impact of an asteroid (some thing a comet instead) in a remote area of Russia called Tunguska on this date in 1908. The blast of the explosion when it hit knocked down an estimated 80 million trees over an area of 830 square miles in eastern Siberia. Witnesses reported seeing a fireball and a shock wave broke windows hundreds of miles away, but no crater was found, leading scientists to speculate that it broke apart while it was still in the sky. You can read more about this mystery at EarthSky here.
