The question of whether the earth will be destroyed by a comet within the lifetime of human existence is a timeless one. Sadly, all those disaster films we’ve seen might not be entirely fictional flights of the imagination. The correct question to be asking, scientists say, is not one of if we’ll be hit, but when. Here’s a few facts to bolster this position:
The earth is already struck by asteroids every year. NASA reports that “as of April 07, 2014, 10897 Near-Earth objects have been discovered.” Most objects that do strike the earth, according to Live Science, are refrigerator-sized and burn up harmlessly in the atmosphere. We did get a sobering “close call” in 1994, however, when Comet Shoemaker-Levy 9 broke into several 2-km chunks that struck Jupiter. The website for the Panoramic Survey Telescope & Rapid Response System asserts that if Earth had been struck instead of Jupiter, we would’ve seen catastrophe on a global scale. And the Tunguska incident, a huge explosion in the Siberian forests caused by asteroid impact in 1908, remains strong in human memory.
Asteroid Apophis is thought to strike the earth in 2036. The evidence for this derives from information gleaned by scientists at the Herschel Space Observatory in early 2013. However, while we know that the possibility exists that Apophis may strike the earth the next time it passes near us (comets and asteroids orbit around the Sun every certain number of years), Space.com reports that the odds have been greatly reduced to those of 1-in-10,000, down from the previous estimate of 1-in-40.
Cosmic collisions are thought to be responsible for species extinctions both major and minor in the past. The earth is over 4.5 billion years old, and in that time we’ve had plenty of ugly run-ins with Near-Earth objects (or NEOs). The best known is the asteroid/comet that caused the destruction of the dinosaurs 65 million years ago. On a more anecdotal note, you don’t even need to rely on the word of scientific journals to understand how enormous a role comets have played in literally shaping the “face” of the earth. On my road trip out West, I encountered the 37-mile-wide Meteor Crater in the Arizona desert, an enormous valley caused by meteorite impact around 50,000 years ago. Seeing the evidence for yourself is enough to make most people think twice about investing in a bomb shelter!