Could speeding space rocks be headed your way?
You stick your fielder's mitt in the air to snap a pop fly. Suddenly, you hear a low, whistling noise and a huge thud. Something falls at your feet. But when you look down all you see is a baseball-sized black rock. You lean down to pick it up, then pull your hand back fast. This rock is hot!
Brodie Spaulding was in his front yard when a rock like that landed. The 13-year-old thought it was pretty weird. So he sent the rock to scientists to find out where it I came from. Minerals in the rock gave them the answer: The rock fell from outer space!
When Space Hits Earth
Dozens of these meteorites fall to Earth each week. Most fall harmlessly onto open land or into the ocean. Nobody's ever been killed by a meteorite. But now, some scientists are asking this question: What if a really big rock — even bigger than the one that made Meteor Crater — came our way tomorrow?
They know where such a big rock could come from. For one thing, an asteroid could break up and send huge meteoroids tumbling in our direction. So could a comet (a giant space chunk of mixed-up ice, rock, and frozen gases). And it's even possible for a whole asteroid or comet to be on a collision course with Earth.
How? Like planets, asteroids and comets each follow an orbit — an oval-shaped path around the Sun. Most of these orbits never meet. But some asteroids and comets move in paths that cross Earth's orbit. If the timing were right, on of these giant space rocks could collide with Earth.
In fact, asteroids bigger than jetliners streak past Earth every few years. Most don't even come as close to Earth as the Moon does. But some get too close.
In 1908, an asteroid or comet bigger than your school sped straight toward Siberia, in Russia. It was moving so fast that it actually exploded in mid-air. The super-hot blowout burned thousands of acres of forest to the ground. Luckily, no one was hurt. People were shaken up, though. One man was knocked off his chair — 110 km (70 mi) away!
And that was nothing compared with the asteroid that may have wiped out the dinosaurs!
Scientists agree that you're not likely to see that big of a crash in your lifetime. In fact, one scientist figures that if you lived 100,000 more years you'd probably face only one asteroid impact that big. The problem is, no one can say when during that 100,000 years it would happen. So some scientists think we should be prepared.
How? The first step would be to identify large asteroids that might be dangerous. Astronomer (space scientist) Eleanor Helin has been looking for these asteroids for years. She's trying to spot the ones that come close to Earth on their way around the Sun. (They're called near-Earth asteroids.) "We have discovered about 300 near-Earth asteroids," says Eleanor. "There are probably about 1,700 more we don't know about.
Eleanor and other space scientists want to build five powerful telescopes to place around the world. They would use the telescopes to track more near-Earth asteroids. Then they could use computers to figure out if (and when) each asteroid might be on a collision course with Earth.
Is it Worth the Search?
Still, not everybody supports the search effort. Why not? For one thing, some say, the chance of a harmful asteroid hitting us is too small to worry about. Second, so what if we spotted an asteroid headed our way. What could we do to stop it?
"Plenty" say some scientists — if we catch it a few years ahead of time. We could try to nudge the asteroid off course, so that it would shoot past Earth. How could we nudge such a heavy rock? "If it's not too big we could ram it with a spacecraft," says space scientist Jack Hills.
Or, if the job needs more power, scientists could send up a nuclear missile. The bomb wouldn't blow up the asteroid — it would explode nearby. "The explosion would make a crater on one side of the asteroid," said Hills. "Rocks and gasses would shoot out of the crater. It would be like the blast from the bottom of a rocket." This "rocket power" would push the asteroid into a new orbit.
Scientists are still debating if and how to plan for a killer asteroid. In the meantime, Eleanor and other astronomers will keep their eyes on the sky, looking to discover more near-Earth asteroids.
As for you, you could keep your eyes on the ground, looking for meteorites. But don't expect to be as lucky as Brodie. You have a better chance of spotting a space rock if you look up. Wait for a meteor shower, at night when lots fall at once. You'll see them streak by as "shooting stars."