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Could a giant space rock strike Earth?

Space rocks have pounded the planets for years. Just take a look at Mercury and Mars. You can see the scars. Yet surely Earth is safe. Right?

Not really. In Australia, there are craters. Those are big holes in the ground. Huge asteroids made them 5,000 years ago. Across the world, these holes can be found. You can also find craters closer to home. Arizona has a huge crater. We once thought a volcano made it. But a speeding asteroid did the deed.

Craters do not last long. Wind and water wear them away. Yet some craters are still around. So we know that rocks hit Earth not too long ago.

Where did those rocks come from? Thousands of asteroids circle our sun. Most are in the asteroid belt. It is an area between Mars and Jupiter.

Many rocks in the belt are pebbles. Some are much larger. Even gathered together, though, they would be smaller than our moon.

Have you heard of the spacecraft NEAR? It crashed into an asteroid in 2001. Before crashing, NEAR took pictures. They showed that the asteroid had craters too.

Should you fear the asteroids in the belt? No. They are not much danger. They stay there for the most part. Others, however, are another story.

Asteroids that come close are called Near-Earth Objects. One such rock was found not long ago.

This asteroid passes Earth every 16 years. Its next visit will be in 2013. It will not come too close to Earth.

Things will be different in 2036. Then it will be much closer. That could cause problems. You see, Earth has a force that pulls on objects.

That is why NASA is sending a spacecraft. It will put a machine on the asteroid. That will help scientists track the rock.

You never know what NASA will find. A Japanese spacecraft visited an asteroid in 2005. It was a pile of rocks. Perhaps this one is too.

Scientists will follow the asteroid carefully. It will most likely miss us.

If not, we could take care of it. We could use spacecraft as tractors. They would pull the rock away. So do not worry. The sky is not falling.

Article by Lesley J. MacDonald. Top-of-page photo by © Don Dixon/cosmographica.com. "Asteroids Rock" appears on pages 18-23 of our September 2006 issue.