New estimates show there are 1,100 asteroids that are more than six-tenths of a mile in diameter near Earth. Chances are slim that one could strike Earth, but if it did happen it could have disastrous consequences as depicted in this NASA illustration. Although space may seem like a vacant place, the inner solar system is crisscrossed by a scattering of rocky, fast-slinging projectiles. And new estimates suggest there may be more traffic out there than previously thought.
Geologic records suggest there is good reason for concern.
Most scientists agree it was a gargantuan-sized asteroid that caused the extinction of the dinosaurs 65 million years ago. And, most recently in 1908, a meteor crashed down in Siberia and devastated more than 1,000 square miles of forest and wildlife. Scientists have determined that an object with a diameter of 10 km or more could extinguish life on earth. Fortunately such collisions only occur once every 100 million years or so. More worrisome are objects six-tenths of a mile or more in diameter that impact the planet every 500,000 to 10 million years.