Is a Doomsday Asteroid Heading Towards Earth?

Asteroid heading towards Earth
Image Credit: NASA

Last year was a tough one, loaded with natural and man-made disasters to the point where many people jokingly predicted a giant asteroid hitting Earth for December 2020. Now that we have safely passed into the New Year, we know that this was false. But could it have happened? What about next month?

Asteroids, meteors and sometimes comets are often the villain in sci-fi plots. Made especially notorious by Michael Bay’s Armageddon to the point where ‘hitting earth’ is one of the top autocomplete suggestions when typing ‘asteroid’ in google. So lots of people clearly worry about a similar situation, but how realistic is that? In short, not very. The longer answer can be split into two questions.

Can a giant, Armageddon-like asteroid hit Earth?

The asteroid in the Armageddon movie is 1,000 km (600 miles) across, which makes it roughly the size of Texas or one and a half times the size of France. It is discovered at a very late stage, less than a year from impact.

There are several problems with that, the main one being that there are no asteroids that big in the Asteroid Belt  or the Oort Cloud. The only thing that comes close is the dwarf planet Ceres, but there is virtually 0% chance of that hitting us as it has a stable orbit. Pluto, Charon and Eris are also contenders, but they too have stable orbits.

Physics help us in this regard, as the amount of energy needed to move something scales with its size. This means that a small pebble can be thrown off course by the lightest touch, but that a giant country-sized rock can’t even be moved when a nuclear missile hits it. This means that most objects with strange orbits are rather small.

On top of that, hundreds of astronomers, both professional and amateur, aim their telescopes at the sky each night. The combined data from these observations allows us to measure orbits of anything in the sky to extreme degrees. An Armageddon-sized asteroid would have to be 50 to 100 times further than Pluto to be dim enough to hide from all the eyes pointed at the sky.

Can an extinction style asteroid hit the Earth?

OK, so we know that a giant country-sized asteroid heading towards Earth is out of the question. But what about something that is a few hundred meter/feet across, like the meteor that killed the dinosaurs?

Smaller asteroids that are about 10 km (6 miles) across are much more common in the solar system. A strike by one of those could end life on Earth, just like it did 66 million years ago. However, like explained above, it would be extremely unlikely that an object of this size could possibly ‘sneak up’ on us. As of yet, there is nothing that comes close to that size heading for us.

The European Space Agency (ESA) maintains an up to date ‘risk list’ of all possible objects that could hit us in the ‘near’ future. There are just over 1000 objects on the list, most of which are below 10m (30ft) in diameter. The largest is 700 meters (0.4 miles) and has a 1 in 3.5 million chance of hitting us in 2056. You can find the complete list here.

Asteroids of these sizes can still be dangerous, but only in a very limited range. For example, the 20-meter 2013 Chelyabinsk meteor that exploded above Russia caused more than 1,500 injuries and millions in damage. This shows that even the small meteors should be taken seriously.

In conclusion, the chance of a giant life-ending meteor are about as likely as a super volcano awakening in the middle of Europe. Smaller ones are possible, but will only cause limited and minor damage. So there is really no reason to worry about them, but do keep an eye on the ESA risk list and the news.

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