Every day scientists and amateur astronomers discover new minor planets, comets, and other pieces of debris floating around our solar system. There are literally hundreds of thousands of pieces of rock and ice moving around our sun. Some of these pieces float in a predictable orbit around the sun, while others seem to move more randomly, making their own way through our local planetary system.
So what are the chances of one of these wayward members of the solar system, such as an asteroid or comet, hitting the Earth?
We know that asteroids, comets, and other types of debris have collided with the Earth in the past. In fact, hundreds of rocks and pieces of dust collide with Earth’s atmosphere every day. They’re so common that we often enjoy catching a glimpse of one of these pieces of debris entering out atmosphere. We call them meteors, and on any given night we can walk outside and watch for one to create an impressive streak of light across the night sky.
Of course most meteors are small. Most are smaller than a penny. But asteroids can get pretty big, as large as 10 miles or more across. If one of these mini-moons were to hit the Earth, the results would be a disaster of epic proportions. This would include catastrophes such as tidal waves, a blocking of the sun, and a possible heating of the Earth’s atmosphere.
There have been a number of asteroids that have made close approaches to the Earth, some even passing within the moon’s orbit. Asteroid 2005YU55 passed as close as 200,000 miles from the Earth, about 50,000 miles closer than the moon, on November 8, 2011. This asteroid is about 1/4 of a mile across and would be seriously problematic for us if it entered our atmosphere.
The odds of a large asteroid actually colliding with the Earth in your lifetime are dramatically small. Space is a very large, vast, and empty void, and the Earth is a relatively small target. The chance of an asteroid of any massive size actually hitting the Earth in the next 100 years are so small, the odds aren’t even worth calculating. The calculated next possibility of a large asteroid hitting our planet is 2182. I wouldn’t lay any bets, however; the odds are only 1 in 1,000.
What can we do if one of these floating giants of the solar system actually presented a danger? Despite what the movies have shown us, we could do nothing. We could launch as many nuclear missiles as we wanted to at it, and despite the fact that actually hitting a moving target with a missile in time to actually do any damage is virtually impossible, the best we could hope for is that the asteroid would break into thousands of smaller pieces. Unfortunately, these smaller pieces would spread out to create a larger impact zone that would affect more people. The truth is, we could do nothing to stop a major asteroid impact on Earth.
Someday, however, a large asteroid or comet will inevitably strike the Earth and cause massive damage. With the number of unknown objects that are out there, and the billions of years that the Earth will be around, it is guaranteed to occur at some point in the future. It’s not a matter of if, but a matter of when. Just don’t hold your breath.