Asteroids Rock
Could a giant space rock slam into Earth in 30 years?
PLANET POUNDING
Space rocks have pounded the planets for years. All one has to do is look at Mercury or Mars to see the scars left by these crashes. Even our moon is scarred. What about our planet? Surely Earth is safe.
Not really. Take Australia, for instance. There you'll find a group of 13 craters. Huge space rocks gouged them out about 5,000 years ago.
Craters are also found in Argentina in South America. There you'll find large teardrop holes in the ground. These formed when a 200-meter (600-foot) space rock broke up as it skipped across the landscape.
Signs of this cosmic beating are also found closer to home. In Arizona, you can find a 1.6-kilometer-wide (1-mile-wide) crater. This is Meteor Crater. A speeding space rock blasted it out about 5,000 years ago.
These aren't the only impact craters. More than 200 have been found. That may not seem like many, but wind and water can erode, or wear away, old craters. They don't last long.
Craters show that space rocks have slammed into our planet. That raises a big question. Could it happen again? To answer that, we have to know where space rocks come from.
ON THE ROCKS
Most space rocks start off in the asteroid belt. It is an area between Mars and Jupiter. Millions of asteroids orbit our sun there. Most scientists think asteroids are leftover material from the formation of our solar system.
The asteroids found there range in size. Most are pebbles. Some are large stones. Other asteroids are 1,000 kilometers (600 miles) across. If all the asteroids were gathered together, though, they would form an object less than the size of our moon.
The NEAR spacecraft crashed into one of these asteroids on February 12, 2001. It's called Eros. It's one of the largest asteroids. As NEAR zoomed in on the asteroid, it took lots of photos. They showed that the asteroid has long grooves. It is also pocked with craters. One of the largest is nearly six kilometers (four miles) across. Unfortunately, NEAR went dead as it crashed into Eros. Still, it showed for the first time what an asteroid looks like close-up.
The asteroids in the asteroid belt do not pose much of a threat to Earth. They stay there for the most part. Some, however, drift out of the asteroid belt. They may come closer to Earth. These asteroids are more threatening.
CLOSER TO HOME
Some asteroids come much closer to Earth. These are called Near-Earth Objects. Take an asteroid named Apophis, for example. This 320-meter-wide (1,050-feet-wide) asteroid was discovered just a couple of years ago. Yet some scientists are already worried about it.
Apophis passes near Earth about every 16 years. Its next visit should be in 2013. That shouldn't cause a problem. It will pass by us harmlessly. This space rock will pass Earth again on April 13, 2029.
This time it will be much closernly 35,000 kilometers (22,000 miles) away. It will be so close that Earth's gravity may change its orbit. Now that could cause a big problem.
TOO CLOSE FOR COMFORT?
Instead of passing by Earth, this asteroid could slam into our planet in April 2036. The most likely spot is off the coast of Mexico.
To learn more, NASA plans on sending a spacecraft to the asteroid. The spacecraft would put a homing beacon on it. That would help scientists accurately track the asteroid.
Scientists have already sent one spacecraft to a Near-Earth Object. Last September, a Japanese spacecraft visited an asteroid slightly larger than Apophis. The space rock is made of boulders. It looks more like a pile of rubble than a solid chunk of rock. Scientists think it formed when two space rocks slammed into each other. Could Apophis also be a pile of space rubble?
By first charting Apophis's path through space and then going there, scientists can decide how to deal with the asteroid. It will most likely never slam into our planet.
If it is ever on a collision course, scientists can take care of the asteroid. They could send a spacecraft to it. The spacecraft would act like a tractor and pull the asteroid away from Earth. So don't worry too much. Even if an asteroid comes close, the sky isn't 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.
Could a giant space rock slam into Earth in 30 years?
PLANET POUNDING
Space rocks have pounded the planets for years. All one has to do is look at Mercury or Mars to see the scars left by these crashes. Even our moon is scarred. What about our planet? Surely Earth is safe.
Not really. Take Australia, for instance. There you'll find a group of 13 craters. Huge space rocks gouged them out about 5,000 years ago.
Craters are also found in Argentina in South America. There you'll find large teardrop holes in the ground. These formed when a 200-meter (600-foot) space rock broke up as it skipped across the landscape.
Signs of this cosmic beating are also found closer to home. In Arizona, you can find a 1.6-kilometer-wide (1-mile-wide) crater. This is Meteor Crater. A speeding space rock blasted it out about 5,000 years ago.
These aren't the only impact craters. More than 200 have been found. That may not seem like many, but wind and water can erode, or wear away, old craters. They don't last long.
Craters show that space rocks have slammed into our planet. That raises a big question. Could it happen again? To answer that, we have to know where space rocks come from.
ON THE ROCKS
Most space rocks start off in the asteroid belt. It is an area between Mars and Jupiter. Millions of asteroids orbit our sun there. Most scientists think asteroids are leftover material from the formation of our solar system.
The asteroids found there range in size. Most are pebbles. Some are large stones. Other asteroids are 1,000 kilometers (600 miles) across. If all the asteroids were gathered together, though, they would form an object less than the size of our moon.
The NEAR spacecraft crashed into one of these asteroids on February 12, 2001. It's called Eros. It's one of the largest asteroids. As NEAR zoomed in on the asteroid, it took lots of photos. They showed that the asteroid has long grooves. It is also pocked with craters. One of the largest is nearly six kilometers (four miles) across. Unfortunately, NEAR went dead as it crashed into Eros. Still, it showed for the first time what an asteroid looks like close-up.
The asteroids in the asteroid belt do not pose much of a threat to Earth. They stay there for the most part. Some, however, drift out of the asteroid belt. They may come closer to Earth. These asteroids are more threatening.
CLOSER TO HOME
Some asteroids come much closer to Earth. These are called Near-Earth Objects. Take an asteroid named Apophis, for example. This 320-meter-wide (1,050-feet-wide) asteroid was discovered just a couple of years ago. Yet some scientists are already worried about it.
Apophis passes near Earth about every 16 years. Its next visit should be in 2013. That shouldn't cause a problem. It will pass by us harmlessly. This space rock will pass Earth again on April 13, 2029.
This time it will be much closernly 35,000 kilometers (22,000 miles) away. It will be so close that Earth's gravity may change its orbit. Now that could cause a big problem.
TOO CLOSE FOR COMFORT?
Instead of passing by Earth, this asteroid could slam into our planet in April 2036. The most likely spot is off the coast of Mexico.
To learn more, NASA plans on sending a spacecraft to the asteroid. The spacecraft would put a homing beacon on it. That would help scientists accurately track the asteroid.
Scientists have already sent one spacecraft to a Near-Earth Object. Last September, a Japanese spacecraft visited an asteroid slightly larger than Apophis. The space rock is made of boulders. It looks more like a pile of rubble than a solid chunk of rock. Scientists think it formed when two space rocks slammed into each other. Could Apophis also be a pile of space rubble?
By first charting Apophis's path through space and then going there, scientists can decide how to deal with the asteroid. It will most likely never slam into our planet.
If it is ever on a collision course, scientists can take care of the asteroid. They could send a spacecraft to it. The spacecraft would act like a tractor and pull the asteroid away from Earth. So don't worry too much. Even if an asteroid comes close, the sky isn't 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.
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