See Neil deGrasse Tyson speak belowWhat's the point of protecting the environment if bad luck brings a big space rock on a trajectory that crosses Earth's path? Even near Earth objects that are not big enough to create an extinction event (we apparently had a near miss in 1883) could cause a lot of damage, on a scale similar to other big natural catastrophes like large earthquakes and super-volcanoes. The main difference is: We can't do much to prevent earthquakes and volcanoes from hitting us (though we can mitigate the impacts by building a more resilient civilization), but we could do something about asteroids if we see them coming far enough in advance and have deflecting technologies available when the time comes. The risks might be low on any single year, but we can't roll the dice forever and just hope our luck will hold; low-risk but high-impact possibilities should be taken seriously.
The United Nations (U.N.) seems to agree:
The U.N. plans to set up an “International Asteroid Warning Group” for member nations to share information about potentially hazardous space rocks. If astronomers detect an asteroid that poses a threat to Earth, the U.N.’s Committee on the Peaceful Uses of Outer Space will help coordinate a mission to launch a spacecraft to slam into the object and deflect it from its collision course. (source)
Surprisingly, no national space agency - not even NASA - is tasked specifically with deflecting asteroids.
So what's the next step? Finding the rocks. “There are 100 times more asteroids out there than we have found. There are about 1 million asteroids large enough to destroy New York City or larger. Our challenge is to find these asteroids first before they find us," said astronaut Ed Lu.
Once you find and track all these near Earth object, you can calculate their trajectories into the future and see if any are dangerous for us. If you know long in advance, it's much easier to try to deflect it; even a slight alteration to its course could make it miss Earth. But if we don't have enough advance warning, there might be nothing that we can do.
Ed Lu is part of the B612 Foundation who's mission it is to do exactly that. They plan to launch a space telescope:l "Sentinel is a space-based infrared (IR) survey mission to discover and catalog 90 percent of the asteroids larger than 140 meters in Earth’s region of the solar system. The mission should also discover a significant number of smaller asteroids down to a diameter of 30 meters. Sentinel will be launched into a Venus-like orbit around the sun, which significantly improves the efficiency of asteroid discovery during its 6.5 year mission."
You can find more about Sentinel here.
And here's a speech given at Stanford in 2009 about the danger posed by Asteroids. If you're a space geek, it's fascinating:
Here's everyone's favorite, Neil deGrasse Tyson speaking on the danger from asteroids:
See also: The Future Ain't What it Used to Be!