Let’s pretend the fly-by asteroid strikes Texas. What happens next?  Today’s the big day, when Asteroid 2005 YU55 will pass within about 200,000 miles of our fair planet, and come slightly closer to the moon tomorrow.

We’re all familiar with asteroids presenting end-of-the-world scenarios because of movies like Armageddon, in which a “Texas”-sized asteroid threatened Earth.

That's laughable of course, because Texas is about 1,400 kilometers across and the largest known asteroid in the solar system, Ceres, measures just 900 km in diameter.

Whatever, it wouldn’t take an asteroid the size of Texas to cause a global catastrophe.  NASA says an asteroid would only need to be more than 2 km in diameter to cause worldwide environmental consequences. And 2005 YU55 is much smaller than that. Which is not to say it would not have an impact.

So what would happen if YU55, traveling relative to Earth at a velocity of 30,000 mph, hits Earth?  Bad things for sure, but not catastrophic things unless it lands on top of you.

Just for fun, let’s say this asteroid hits land about 100 miles west of Houston, like Schulenburg.  It would probably produce a crater about 4 miles across.

The initial impact would also produce a shockwave and winds that would move out 360 degrees at about 35 mph, and sound something like very loud traffic.

We would also have seismic shaking equivalent to about a 6.8 magnitude earthquake that would be felt for hundreds of miles around, and there would be a lot of dust in the air.

And this is just a small asteroid. Imagine what a really big one would do.

via Let’s pretend the fly-by asteroid strikes Texas. What happens next? | SciGuy | a Chron.com blog.

No need to panic.  NASA says this asteroid will not strike the Earth.