What If an Asteroid Were on a Collision Course to Hit Earth?

Somewhere in the far reaches of space, a giant hunk of rock is hurtling our way, just bidding its time before an extinction level impact with Earth. Before you run into your bunker or panic by a year's supply of toilet paper, stay calm. Oh my God. OK, it's happening. We have a plan. While we've encountered deadly asteroids in our past, do we have the technology now to stop them in their tracks? What size does an asteroid need to be to wipe us out? Are there any asteroids heading our way in the near future, and should we blow them up or push them out of the way? This is What If, and here's what would happen if an asteroid were on a collision course to hit Earth. Here at What If, we've covered asteroid impacts many times. And yeah, a lot of people and dinosaurs have died in our videos. But instead of all the doom and gloom in this episode, we're fighting back using science and lasers. You might be wondering, are there any deadly asteroids out there coming our way? Well, NASA has identified 1 potentially threatening asteroid known as One O 1955 Bennu, or just Bennu for short. This ancient asteroid weighs over 71 billion kilograms in it has a one in 2700 chance of colliding with Earth in the year 2185. Phew. OK, well we have a bit of time, but our great great great great great great grandchildren might not unless they get their acts together. So how exactly can we prevent an asteroid impact? Well, there are a few ways to stop an asteroid. Your first instinct might be to blow them up like in the movies. Now while nuking an asteroid is a possibility, it all really depends on its size. To put this into perspective, it would have taken a nuke 2000 times more powerful than the biggest nuke ever created to destroy the asteroid that killed the dinosaurs. In the case of the movie Armageddon, if a 12187 kilometre wide asteroid were going to hit Earth in an hour, we would need to blast it with as much energy as the total energy output of the sun in a day. That's a lot of firepower. Bruce Willis would have to get out of there pretty quickly, or he'd die hard. In some cases, nuking a large asteroid wouldn't do any good, as the gravitational pull of its core could pull it all back together. All right, so if we can't blow it up, what else could we do? Excuse me. Yes, sorry. But I have a suggestion. Why don't we just nudge them a bit? Well, that's not actually a bad idea. Adding or subtracting just 0.03 meters per second of velocity to an asteroid can be just enough of a push to keep us out of harm's way. This could be achieved by an explosion about 300 meters away from the asteroid. The irradiation from the explosion will cause a layer of the asteroid's surface to heat up and blow off, pushing in the opposite direction. Another idea is to slam a spacecraft into it at just the right angle. This is known as the kinetic impactor option. Kind of like space billiards. 8 ball corner pocket. In the year 2022 this method will be tested on a non threatening asteroid just to see if it works. This will be the double asteroid redirection test, otherwise known as the DART mission. Nice one NASA. I like DARTS, too. 182 spacecraft will head toward a double asteroid called Didimos, accompanied by its smaller companion, Didimoon. Perfect names for your future cats. One spacecraft will slam into Didimoon in just the right spot and bullseye. It will nudge its orbit just enough to push Didimos away. The other spacecraft will then monitor its orbit and trajectory. Another option is to fly a spaceship close to an asteroid and gravitationally nudge it over time. But this would be pretty expensive and tricky, and not all of us can maneuver like Han Solo. So what is a cost effective way of stopping an asteroid? How about a laser? If it can move your cats out of the way, then maybe it could do the same for an asteroid. A numerical study has shown that by firing a powerful laser on an 80 meter wide asteroid for a month, it could heat it enough to move it the equivalent distance of two earths away. As the asteroid surface heats up, it ejects material, creating thrust. NASA's Planetary Defence Coordination Office has also proposed that a spacecraft could be sent out with a less powerful laser array to orbit the asteroid, but it would have to get to the asteroid 15 years in advance to pull this off. Luckily, we can detect threatening asteroids well ahead of time using powerful telescopes. By taking continuous pictures of the sky, astronomers use computers to look for movement across the background of stars. However, some asteroids, like the Chelyabinsk asteroid that struck Russia in 2013, can go unnoticed. That's because smaller asteroids won't shine as bright as bigger ones. They have to come very close to Earth to be detected by ground based telescopes. Thankfully, the Russian meteoroid exploded 30 kilometers above the city of Chelyabinsk before it could do any serious damage. This still resulted in a powerful shockwave that shattered windows and injured around 1500 people. NASA has classified over 21,000 asteroids and 100 comets as near Earth objects. Only two thousand of these are considered potentially hazardous. This means that their orbits are within 7.2 million kilometers of Earth, and they have to be bigger than 800 meters to lead to a global catastrophe. And before you freak out, the odds of being killed by an asteroid are around one in 250,000. You're way more likely to die in an airplane crash or an earthquake, but you'll sleep better knowing that both the European Space Agency and NASA have panels of experts that have been planning asteroid defence strategies for decades. Now, if you want to know what might happen if a massive asteroid hit us, well, doomsday preppers, you're in luck. Because that's a story for another What if?