Just four days ago, we dodged a bullet ... figuratively. An asteroid named 2012 DA14 passed by the Earth at a distance of about 17,000 miles and traveling at 4.8 miles per second. That's over 10 times the speed of a bullet. Placing it inside the orbits of geosynchronous satellites, it was the closest approach to Earth by an object of that size which we have been able to track as it approached. A recently discovered asteroid (in 2012), it spans a width of about 160 feet. What could it do to us if it were to strike the Earth? Similar sized objects have targeted Earth in the past. The Tunguska blast of 1908 which leveled 200 square miles of forest in the remote Tunguska region of Siberia and Barringer Meteor Crater in Arizona, produced by an impact 50,000 years ago, were both caused by similar sized projectiles from space. Both of those locations were desolate regions at the time of impact. If such an object were to strike a populated area today, it would be devastating for hundreds of miles around the impact site but it would not be an extinction level event like it was for the dinosaurs. The rock that took out the dinosaurs and about two-thirds of the species on planet Earth at that time was about 6 miles across much, much larger than DA14.