Could We Stop an Asteroid?

Asteroids are rocky objects left over from when the Solar System first formed. When they hit Earth, they are called meteorites.

Most meteorites are small and pass unnoticed but bigger ones can be disastrous. After all, when a meteorite struck near Chicxulub, Mexico, the heat it produced wiped out around three quarters of the species on Earth—including the dinosaurs.

When an asteroid enters the Earth’s atmosphere, it’s called a meteor. Meteors burn up in Earth’s atmosphere without striking Earth. Have you ever seen a “shooting star”? Those aren’t stars at all. They’re meteors!

In 2013, a meteor burst over Chelyabinsk, Russia. It injured over a thousand people and caused all kinds of damage to the town.

If an asteroid is small enough, it will explode when it impacts the Earth’s atmosphere. That’s what happened with the Chelyabinsk meteor. It was only 20 metres in diameter.

But the bigger the asteroid, the more damage it can cause. According to Science educator Bill Nye, asteroids with diameters between 25 metres and 45 metres could wipe out an entire city or county. Asteroids with diameters of 100 to 140 metres could wipe out a whole country. Asteroids any bigger than that could wipe out an entire continent. And, as we know, really big asteroids can wipe out huge amounts of life.

Because space is so vast, astronomers estimate that there are many huge asteroids that humans have not detected. Some astronomers estimate that there are approximately 17 000 near-earth asteroids larger than 140 metres in diameter that are undetected. In December 2018, a meteor exploded over the Bering Sea. Nobody noticed it until it exploded!

To detect asteroids, Bill Nye suggests building a special satellite. This satellite would be positioned around the orbit of Venus. The satellite’s rear would point to the Sun. This way, it would be able to detect asteroids with infrared light.

Imagine this spacecraft detected an asteroid charging toward Earth. The next step would be to deflect it (change its direction), so that it wouldn’t strike Earth. One way to deflect an asteroid is to change its speed. If an asteroid is travelling 10 km/second, reducing its speed by 2 mm/second would be enough to deflect it. Since asteroids can be very large, changing its speed even a little can make it change course. 
Don’t forget, an asteroid can weigh 10 000 tonnes or even 100 000 tonnes. Changing the speed of such a large object would take a lot of force! The easiest way to change an asteroid’s speed would be to send a rocket to crash into it, but this might break the asteroid into pieces. Instead, astronauts could send a really big spacecraft out to get close to the asteroid. The gravity of the spacecraft would tug the asteroid slightly in another direction. However, this is not an easy solution. The spacecraft would require an enormous amount of fuel.

Another way around this problem is to use laser bees, which are sunlight-powered lasers. They would surround the asteroid and zap its surface. This would cause the surface of the asteroid to begin to vaporize. Large pieces of material called ejecta would be thrown from the surface of the asteroid. The ejecta would have momentum. This method could indeed change the asteroid’s speed.

Scientists estimate that dangerously large meteorites only hit the surface of the Earth every several thousand years. Still, it’s possible that one may hit Earth within our lifetime. That’s why scientists are always trying to find new ways to detect and deflect dangerous asteroids, and keep us safe!