By Teodor Teofilov

Most humans live in blissful ignorance about the world that they inhabit. Be it the biological construction of how life works, or the complex nature of financial markets, it is impossible for a single person to be well versed in every area. People can spend most of their life without knowing the engineering of their own car, let alone know the process of genetically modifying crops.

And that is normal. We all have different worries that impact our daily lives and tend to ignore large scale problems and events because they simply have no effect on us personally. The Scary Science series aims to show that some of our day-to-day issues can be inconsequential in the grand scheme of things and that there are some truly terrifying scientific theories. Here we will examine theories that can end the world as we know it, making humanity extinct, and in some cases destroying all life on the planet, and there might be nothing we can do.

This series might cause sleepless nights of overthinking human insignificance and bring about existential crisis for everyone who reads it.

In this piece we examine the difficulty in protecting our planet from asteroid collision.

A bad day for dinosaurs

The dinosaurs had a bad day about 65 million years ago when a big chunk of rock roughly 10 km (6 miles) across traveling at 50 times the speed of a rifle bullet hit the Earth. It released its energy all at once and created a crater (the Chicxulub crater) about 180 km (110 miles) across. The power of the explosion would have released more than a billion times more energy the atom bombs that destroyed Hiroshima and Nagasaki combined. This threw vast quantities of debris into the atmosphere and severely altered the planets climate, ultimately leading to the extinction of around three quarters of the species that existed at the time, including the dinosaurs.

There are many asteroids — rocky, metallic bodies that orbit the Sun — of this type that we know of and their orbits pass through the inner solar system and pass through the Earth’s orbit. It is possible in the future that one of these could potentially hit us again. However, most, not all, are smaller than the one that hit us 65 million years ago.

Just four years ago on Halloween a massive roughly 640 meters wide (2,100 foot) asteroid named 2015 TB154, which had the shape of a skull (fairly appropriate) came within 480,000 kilometers (300,000 miles) of our planet. The moon orbits at an average distance of 384,600 km or 239,000 miles.

Assuming that 2015 TB154 had an entry speed of 17 km/s (10.6 miles per second) and a density of 2,600 kg/m3 (approx. 162.3 lb/ft3), it would have impacted our planet with 2,800 megatons, which is 56 times the force of the most powerful themornuclear bomb that humanity has ever detonated — the Tsar Bomba. To compare, the Tsar Bomba had a yield that is 1,570 times the combined force of the bombs dropped on Hiroshima and Nagasaki.

So getting hit with an object like 2015 TB154 would mean massive destruction in a large area around the point of impact, devastation of life around and most likely climate disturbance that will have cataclysmic consequences around the world.

However, asteroids don’t necessarily have to hit the Earth to do damage. In 1908, near the Podkamennaya Tunguska River in Siberia, Russia, an asteroid estimated to be between 60 to 190 metres (200 to 620 feet), depending on its constitution, exploded around 5 to 10 kilometres (3 to 6 miles) above the surface of the Earth. The explosion over the sparsely populated area flattened 2,000 square kilometres (770 square miles) of forest.

It has been estimated that the speed of the asteroid was traveling at a speed of about 15 km/s (9 miles per second) and that during its fall, the 100-million-kilogram (220 million pounds) rock heated the air around it to 25,000 degrees Celsius (44,500 Fahrenheit). The power of the explosion of the asteroid is equivalent to about 185 Hiroshima bombs. If this were to have happened above a city, it could have done a huge amount of damage, especially if it happened to a city that we rely on more on the global economic basis.

However, such large scale events aren’t a normal occurrence. According to NASA, every day the Earth is hit by more than 100 tons of dust and sand-sized particles, and about once a year a car-sized asteroid burns up in the atmosphere, creating a spectacle of light in the sky. Every 2,000 years or so a football field sized object hits us and causes damage to the area and only once in a few million years comes an object big enough to threaten the existence of life.

So how many asteroids are there in the solar system? Well, a lot.

Great video courtesy of  Scott Manley that shows asteroid discovery

As of March 28, 2019, there were 796,026 known asteroids. It has been estimated that the asteroid belt contains between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 mile) in diameter, and millions of smaller ones. The more dangerous ones are the Near-Earth Asteroids (NEAs), of which we have cataloged 20,226 as of June 2, 2019, with 895 of them being over 1 km in size (0.6 miles).

Although this sounds like a lot, the distance between objects is in the asteroid belt is greater than a million kilometers (600,000 miles). In other words, you can fit about 25 Earths between asteroids.

Can we do anything?

Now the first step that space agencies and countries around the world have already taken is to track asteroids in the night sky and calculate their trajectory. It is difficult to spot them but we are getting better and are building telescopes that are looking for the threat.

But what do we do once we discovered a dangerous rock that is on a collision course with our tiny blue planet?

Lets take the asteroid named Apophis — Egyptian “lord of chaos.” It was discovered in 2004 and will pass close to the Earth in April of 2029. How close? It will pass extremely close and it is possible our planets gravity will distort the asteroids orbit so that it will collide with our planet sometime in the future. It was believed that it might hit Earth in 2036, but scientist ruled that not to be the case. The chances of it’s path being change in such a way are minuscule, but lets assume that it might meet the criteria and come around to bite us. As it is about 370 meters (1,210 ft) in size it isn’t going to end the world, but it could destroy a city easily.

So what can we do about it?

Well, there a numerous solutions that scientists have come up to potentially save our planet from an impact with an asteroid, and no, sending Bruce Willis to blow it up isn’t one of them. As we can’t move the Earth out of the way, we will need to move the asteroid. It turns out we have actually done this before, though not on purpose. NASAs Deep Impact probe slammed into a comet in order to see what is underneath the surface, but the impact did move the comet a little bit.

Comet impact video courtesy of NASA/JPL/UMD

One option that comes from movies is to fire a nuclear bomb at it and hope to alter its course, but there are some problems with that. First of all, it will require a lot of precision, as we have to blow up the nuclear weapon within a small time window. Also the explosion itself might work for an object of the size of Apophis, but for larger ones it will simply make more bullets that will bombard us. A small nudge could move it out of the way of Earth, or it could put it into another collision course with us a couple of years later. But time is good to have.

The biggest problem is predicting and keeping an eye on what asteroid will hit us. If we have time we will be able to do a lot to divert it and protect our planet. We could use so called slow-push or -pull methods to gradually change the orbit of the rock. These can be a constant bombardment of plasma from a spacecraft that flies alongside it, or we could paint it white and let the sun slowly move it. We could also send a satellite that weighs a couple of tons to just fly next to it — the gravity of the asteroid will pull the satellite and the minuscule gravity of the satellite will slightly pull the asteroid by using its boosters gently.

However, all of the strategies that we have require time to implement.

The problem with most solutions is that we simply don’t have the technology available. Even if we had everything prepared and the rocket to carry out our plan, time would likely be our enemy as it would take months or even years to get it all off the ground. Some space missions can take years to launch, which isn’t great. After all, unlike Apophis, the 2015 Halloween asteroid was only discovered three weeks before it passed by the earth. Taking into consideration the distance we need to cover and the fact that most of our solutions will require a lot of time to take effect, we wouldn’t have had time to do anything if it struck us.

With technological advances and our ever improving observation we are very likely to be able to find such asteroids, the only question is if we will find them in time. Although the chance of an Armageddon level asteroid hitting us is very low, we still need to prepare and hope for the best.

 

You can read the previous Scary Science here.

You might also want to check out the danger that space debris pose here.

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Posted by Perfectly Plain

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