Asteroids, also called minor planets, are rocky chunks of debris from space that measure anywhere from a few feet to around 0.6 miles in diameter. Comets are also fragments of ice, dust, and rock but have a condensed core known as a nucleus. Scientists estimate there are probably more than 1 million near-Earth Objects (NEOs) measuring more than 100 meters in diameter and posing a threat to impact Earth in the next century. When an asteroid or comet strikes our planet, it’s called an impact event. There has been only one recorded impact event so far with evidence that it happened: The K-T Extinction Event 66 million years ago when an asteroid struck Earth and wiped out the dinosaurs. The question is, what happens when asteroids hit the Earth?
How Many Asteroids Have Hit Earth?
The number of impact events is a tough thing to calculate because many of the rocks are so small they burn up before they hit the atmosphere. Also, the Earth’s surface erodes over time, so evidence of impacts is hard to find.
The most famous and destructive asteroid impact event in recorded history happened in 1908 in Siberia. An asteroid about 60 feet in diameter entered the atmosphere at 32,000 miles per hour, the fastest speed ever recorded for an impact event.
The asteroid exploded in the air the Tunguska River, releasing about 500 times the energy of the atomic bomb dropped on Hiroshima. About every 10 years, an asteroid about the size of the one that hit Tunguska, or larger, is expected to smash into Earth somewhere.
These “city-killer” asteroids are large enough to be seen from a long way off by astronomers. They are also big enough to survive the trip through the atmosphere and hit the ground.
The Effects of an Asteroid Collision
When an asteroid hits the atmosphere, it heats up and breaks apart, creating a large fireball and shockwave that can destroy a wide swath of the surrounding area. If the asteroid is large enough, it will punch through the atmosphere and slam into the ground, creating an impact crater and releasing large amounts of dust and gas into the atmosphere.
If the asteroid hits the water, it will create a giant tsunami that can devastate coastal areas. There are also indications that an asteroid collision can set off earthquakes, volcanoes, and other natural disasters.
During the impact event, a lot of the energy from the asteroid will be transferred to the air, creating a shockwave that travels at supersonic speeds.
The shockwave will do two things: It will push the air ahead of it and create a loud noise. And it will suck the atmosphere behind it, creating a vacuum that can suck people and objects off the ground.
What Happens When Asteroids Hits the Earth?
If the asteroid is big enough, it will punch a hole through the crust, go through the mantle, and then hit the core. If the asteroid is smaller, it will hit the crust and bounce up again, leaving a large crater. The amount of damage an asteroid will do depends on its size and composition, where it hits, and what direction it hits from.
How Are We Knowing Which Rocks to Watch?
Asteroid detection is a tricky business. Scientists use optical telescopes to identify potential threats, but the smaller the asteroid, the harder it is to detect. The best way to find asteroids is to survey the sky and build up a database of potential threats over time.
There are several organizations and asteroid surveys already doing this. And there is a growing network of people around the world who are learning how to hunt for asteroids.
Strategies to Defend Against Asteroids
There are many ways we can defend against asteroids before they hit us. The first line of defense is to find them early and predict where they will hit. Then we can try to divert them away from Earth. Shortly, we could mount rockets on top of giant lasers to create a giant push against the asteroid to nudge the asteroid off course.
Another idea is to place small rockets on the surface of an asteroid to propel it away from Earth. Asteroid mining could provide a third line of defense against asteroids.
By harvesting material from asteroids, we could produce fuel for rockets and other supplies for deep space exploration. Asteroid mining could also provide resources for deflecting asteroids.
Conclusion
Asteroids are fascinating objects, and some of them can be dangerous. Scientists are tracking most of the big ones and studying smaller asteroids, too.
That way, we can be prepared for the rare but inevitable times when an asteroid does hit Earth. There are about 1,000 known asteroids and comets that have the potential to strike Earth.
