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What would it take to destroy an asteroid? The power of 10 million nuclear weapons.

If you were a movie gallery at the end of the 90s, I would not blame you for believing that the best way to handle an apocalyptic size asteroid that wounds the earth is to blow it to the blacksmith. That's how Bruce Willis saved the world in Armageddon . Saving the planet should be as easy as the press of a thermonuclear button, right? Not so fast. For one, planetary protection experts (a real thing) say it would be much easier to just drive a lethal incoming asteroid into a safer orbit. This is a real consideration, because NASA is watching about 2,000 "potentially dangerous" objects that are within 4,477,790 miles of the Earth and are large enough to damage. But there are also the following: New research suggests that it is really difficult to powder an asteroid. How difficult can it be to destroy a 1 0 kilometer long asteroid? Kaliat Ramesh is Professor of Mechanical Engineering and Materials Science at Johns Hopkins University. And recently, he and colleagues published a paper in the planetary journal Icarus which basically asked the question: What would it take to break up an asteroid? The answer to that question is important – but not so much for what it means for the future of life on earth. Instead, it helps us better understand what asteroids look like, and how they develop over time when asteroids collide with each other. First, there is no way to do this type of exercise without…

If you were a movie gallery at the end of the 90s, I would not blame you for believing that the best way to handle an apocalyptic size asteroid that wounds the earth is to blow it to the blacksmith. That’s how Bruce Willis saved the world in Armageddon . Saving the planet should be as easy as the press of a thermonuclear button, right?

Not so fast. For one, planetary protection experts (a real thing) say it would be much easier to just drive a lethal incoming asteroid into a safer orbit. This is a real consideration, because NASA is watching about 2,000 “potentially dangerous” objects that are within 4,477,790 miles of the Earth and are large enough to damage.

But there are also the following: New research suggests that it is really difficult to powder an asteroid.

How difficult can it be to destroy a 1

0 kilometer long asteroid?

Kaliat Ramesh is Professor of Mechanical Engineering and Materials Science at Johns Hopkins University. And recently, he and colleagues published a paper in the planetary journal Icarus which basically asked the question: What would it take to break up an asteroid? The answer to that question is important – but not so much for what it means for the future of life on earth. Instead, it helps us better understand what asteroids look like, and how they develop over time when asteroids collide with each other.

First, there is no way to do this type of exercise without making any assumptions.

While we know that asteroids mainly consist of iron and stone, we have limited data on their surface and interior. The vulnerability of all rocks to destruction is strongly dependent on how many cracks, pores and other such deformities are on its surface. But Ramesh and his colleagues were able to take the results of experiments on Earth – experiments with very high-speed cameras studying how rocks here on Earth burst and burst as they hit a projectile – and extrapolate them to the low-gravity environment of the space around an asteroid.

Smashed, fissuring stones are a complicated thing to model in a computer. When cracks form on the surface, “you suddenly get this collective behavior of cracks that everyone is trying [move] really quickly, everyone interacts with each other,” Ramesh says. How fast spreading and cracking the many cracks helps to determine the rock’s suspension. So it is a massive complicated process to predict how a collision will change or deform a rock in space.

These limitations aside, Ramesh and his colleagues decided that it would be very difficult to destroy an asteroid – almost impossible. Although there is an asteroid moving toward the earth, it would not make much sense to launch the world’s entire nuclear arsenal on it in the hope of inflating it.

“We would appreciate that it would correspond to about 200 gigatons of TNT to completely disrupt a 20-kilometer diameter asteroid,” Ramesh says. (This is about twice the size of the asteroid or comet estimated to have killed the dinosaurs. But there is some evidence that the Earth has been struck by a massive 20-kilometer asteroid earlier.)

200 gigatons of TNT (dynamite) contain approximately energy equivalent of about 10 million bombs in Hiroshima size. It is also about 10 times more energy than previous estimates of what it would take to destroy an asteroid of this size. (This new estimate takes into account the complex interactions between small cracks forming on the surface of the asteroid at impact, which actually makes a more impact-resistant object.)

The most powerful bomb in human creation had an explosive yield of 50 megatons. You would need the power of 4000 of those who obliterate a 20 mile long asteroid. But even then you can’t just start 4000 nuclear weapons to destroy the asteroid. That energy would have to be delivered with a certain momentum (that is, movement limited to a certain mass). That is, you would probably have to limit the power of 4000 of the most powerful nuclear bombs to a projectile.

This research is not really about destroying asteroids. It’s about what to expect when we visit them.

The huge amount of energy needed is why we do not want to blow up an asteroid to save the earth.

But Ramesh emphasizes that his research is not just about destroying an asteroid on a collision course with the earth. He is well aware that it would be much easier to just drive an asteroid out of the way. (As something, NASA has some preliminary plans.)

In the paper, Ramesh and his colleagues did not model what a nuclear explosion would do for an asteroid. No, they modeled something that happens naturally: What happens when a smaller asteroid strikes into a larger one that has been constantly over the life of the solar system?

The answer to that question helps us understand which asteroids can look like if we were to explore more of them and predict what might happen if we wanted to mine them (possibly with explosives). Asteroids are rich sources of metals, minerals and even water. They can one day provide the raw materials to refuel the spaceships without having to return to Earth.

Eventually, “people and robots will go to an asteroid, and we want a sense of what we should see when we get there,” says Ramesh.

Some robots already have. NASA’s OSIRIS-REX is currently revolving on the asteroid 101955 Bennu, with the ultimate goal of collecting material from its surface and returning it to Earth by 2023 (a similar Japanese mission took asteroid dust back to Earth in 2010). NASA’s Dawn spacecraft flew by the dwarf planets (which can also be regarded as very large asteroids) Ceres and Vesta in 2012 and 2015, respectively. NASA has laid the foundation for a possible “asteroid redirect” mission. Plan: A robot spaceship will land on an asteroid, take a stone and circulate it around the moon.

Asteroids – which people may want to explore or my one day for raw materials – have been subjected to such collisions over the lifetime of the solar system. By imagining how the asteroids collide and are destroyed (or not), we can better understand their composition and surface functions, and how they evolve as more collisions occur. “We would predict what we would find on an asteroid surface if we were to visit one,” Ramesh says.

When a large asteroid is pummeled by a smaller one, gravity holds much of it together.

A fascinating thing that happens when an asteroid is hit but not destroyed is that much of the rubble flying out after the collision is eventually pulled back towards the intact core of the asteroid via gravity. We can very well find asteroids that have these rubies loosely attached to the surface (and are therefore easy to mine). Here is an animation of this memory process that is generated by the researchers’ model.


Charles El Mir / Johns Hopkins University

These calculations also help us understand that if we were to destroy at least part of an asteroid, we would also be able to create more dangerous objects.

The good news is that asteroids that constitute an existential threat to life on earth only strike once every 500,000 years or more. Even the 140 meter wide asteroids that can destroy cities and regions hit once every 10,000 years. And the risk of even being injured from a 20 meter object – like the one that exploded over Chelyabinsk, Russia, 2013 and wounded nearly 1500 people – is small.

So instead of being worried about asteroids that kill us, we should look at them under investigation. Asteroids are fascinating because they represent the planet’s leftover building blocks in our solar system. “You have all these bodies that have been around for several billion years,” says Ramesh. “In order for us to understand the processes that drive these things over time, it is tied to the history of where we come from, and it is also tied to our future when we go out into the solar system and try to use them.” [19659028] Additional reading: asteroids!

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