Asteroid impacts occur rarely, but they can be devastating. The last significant impact was 65 million years ago,
when a huge asteroid struck the Yucatan Peninsula off Mexico, causing mass extinctions and changing the course of life on Earth.
There are currently over 100,000 known asteroids in our solar system. Most of them are too small to see or track, but some are big enough to threaten Earth.
Asteroids are one of the biggest threats to life on earth – so, how often do they actually hit the earth, and are we overdue?
What Is An Asteroid?
Asteroids are rocky objects that orbit around the Sun. Some are very large, like Ceres, which is larger than the Moon and contains more than half of the asteroid belt’s mass.
Others are much smaller, about 50 feet across. They range from fluffy rubble piles just a few yards across (like 2013 WF9) to massive frozen heaps hundreds of miles wide (like Vesta).
In between these two extremes are thousands of objects with their own unique characteristics. It’s fair to say most asteroids have never been visited by human beings – until now.
The Dawn spacecraft arrived at Ceres in March 2015. Dawn has revealed astonishing new details about this dwarf planet, including its mysterious bright spots.
Why Are Asteroids Dangerous?
The main danger posed by an asteroid strike is the damage it could cause. A direct hit would almost certainly destroy any structure built on the object’s surface.
Even if the asteroid missed, there’s still a chance of significant damage being caused by debris kicked up into space.
This is what happened to Tunguska in 1908: a comet exploded overhead, creating a shockwave that knocked down trees for hundreds of square kilometers around.
How Close Has Earth Come To Being Hit By An Asteroid?
Earth has come within striking distance of several asteroids, but none have ever impacted us. In fact, the closest approach was only 24,600 miles away in 1866.
That’s less than 1/10th the average distance from the Earth to the moon.
However, the chances of an asteroid hitting Earth are increasing as time goes on. As the number of asteroids increases, so does the likelihood of one colliding with Earth.
We don’t know exactly why this happens, but scientists think it may be due to gravitational interactions with Jupiter.
How Are Asteroids Tracked?
Most asteroids are discovered before they get anywhere near Earth. When astronomers find something unusual moving through space,
they follow it to learn where it came from. If the object turns out to be an asteroid, they try to calculate its trajectory.
This involves measuring its speed and direction and working out how long it will take to reach Earth.
Once it gets close enough, telescopes are used to study the object. Scientists can also use radar to look inside asteroids, giving them information about their composition and shape.
How Do We Define A ‘Close Call’ With An Asteroid?
An asteroid is considered a potential impactor when it comes within 0.05 AU of Earth. Anything closer than that is likely to miss.
However, even though it misses Earth, it’s possible that the asteroid could collide with another body in the Solar System. So, the term “close call” isn’t quite right.
How Often Do Asteroids Hit Earth?
Every day, somewhere between 15-20 tons of rock hit Earth. Most of them burn up in the atmosphere or break apart in the oceans, but some make it to the ground.
For example, in February 2013, a meteorite exploded over Chelyabinsk, Russia, and more than 1500 people were injured when glass windows shattered all over town. Fortunately, no one died.
Although these small-scale asteroids pay more frequent visits to earth, large-scale encounters are rare. In fact, only once every million years is an asteroid big enough to cause severe damage.
The last giant asteroid to hit earth was 65 Million years ago. It created a crater 66km wide in Mexico and killed off the dinosaurs.
When Will The Next Asteroid Hit Earth?
You may be thinking that if the last extinction-level asteroid to hit earth was 65 million years ago, then we must be overdue for another.
However, you’d be wrong. There’s nothing special about 65 million years ago – it just happens to be the most recent time that an asteroid of that size has been spotted.
Scientists predict that the next potentially dangerous asteroid will probably be found in 2027. It’ll pass by at around 25 times the distance between Earth and the Moon.
This means that it won’t actually strike Earth, but it could still cause damage.
So far, there hasn’t been any sign of an impending collision. And there’s no reason to believe that this particular asteroid will be any different.
However, scientists have warned us not to relax too much. Instead, they say that we should keep a watchful eye on the sky until the next potentially hazardous asteroid passes by.
What Happens When An Asteroid Hits?
When an asteroid strikes Earth, it creates a massive explosion. It doesn’t matter whether the asteroid is made of metal or ice; it makes little difference to the force of the blast.
The energy released by the impact is equivalent to millions of tonnes of TNT exploding every second. If the asteroid is traveling fast enough,
it can create a shockwave that can travel thousands of miles across the surface of the Earth. This causes huge amounts of damage, including the destruction of property and injury to human life.
If the asteroid is moving slowly, it might generate a tsunami. These waves can travel hundreds of miles inland and destroy everything they touch.
If the asteroid is big enough, it can trigger earthquakes. Scientists think that the asteroid’s impact caused the Cretaceous–Paleogene mass extinction event 65 million years ago.
This was a period where many species went extinct, including the dinosaurs.
What Can We Do About Asteroids?
There are many ways we can protect ourselves against impacts from asteroids. One option is to build structures underground.
We could also move cities or other settlements away from the point of impact or use rockets to deflect the incoming asteroid.
Asteroids are usually discovered before they get close enough to pose a threat. So, if we know that an asteroid is heading our way, we can send out warning messages to people who live near the area.
Then, when the asteroid gets closer, we can launch a rocket into space to push the asteroid aside.
This method isn’t perfect, though. Sometimes, the asteroid is so big that even with all the help we can give it, it still hits the Earth.
In fact, some scientists think that there’s only a one percent chance that this will happen. But, if it does, the consequences would be devastating.
There’s no doubt about it: if a large asteroid hits the earth, the consequences would be devastating.
Although asteroids pose a real and very significant threat to life on earth, they rarely collide with us at a size and force large enough to cause any major damage.
Although the threat of an asteroid collision remains relatively low, there’s never a guarantee it won’t happen.
Thankfully, with the power of science and technology, we are well equipped to handle the threat and protect our planet from its devastating impacts.
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