How Worried Should You Be About a Space Rock Destroying the Earth?

It’s the stuff of disaster movies and sensational headlines: An asteroid, meteor, or comet is headed toward Earth. Are we doomed? Isn’t this what took out the dinosaurs? Will we have enough lead time to put our differences aside, come together as a species and mount some kind of technological defence and/or effort to preserve our way of life before we’re totally obliterated, or will we spend our final moments bickering over nonsense?

Let’s not get ahead of ourselves. Most of those questions are moot, because the likelihood of experiencing a humanity-destroying impact is actually pretty low. Here’s what you need to know.

First, what is the difference between a meteor, an asteroid, and a comet?

According to NASA, meteors, asteroids, and comets are “all planetary objects orbiting the sun,” but they are slightly different. Asteroids are small and rocky, look like a point of light when seen through a telescope, and are usually found in a ring between Mars and Jupiter. Meteors are actually meteoroids that have gotten close to Earth and entered our atmosphere — but what is a meteoroid? Those are little pieces of asteroid or comets, from pebble-sized rocks to one-metre chunks, usually resulting from a collision of some sort. Meteors enter the Earth’s atmosphere at a super high speed, burning up and producing a streak of light in the process. (That’s how we get shooting stars.) If a meteor survives all of that and lands on the ground, it’s called a meteorite. Meanwhile, comets are large objects made of dust and ice that orbit the sun and have streaming tails. They’re billions-of-years-old leftovers from the formation of the solar system.

It is cool to know the difference, but not really that important when it comes to the question of the day (how dead will this space rock make us?), because is the same: No one of them is worth worrying about more than any other, and none of them are really worth worrying about at all when there are so many more tangible threats to humanity’s future to keep you up at night.

How scared should you be of a collision?

Famous and mundane meteorite impacts have been recorded throughout history. People have even been injured by glass and debris associated with these rock falls, but according to NASA’s Bill Cooke, only four major meteorites in recorded history have caused any kind of significant damage.

Gordon L. Dillow published a book on this topic in 2019. At the time, he told Smithsonian Magazine, “Earth is bombarded all the time by small asteroids that burn up or explode harmlessly in the atmosphere.” It’s a normal occurrence, planetarily speaking, and rarely causes issues for anyone. Plus, “the chances of a civilisation-ending collision with a large asteroid or comet — like the six-mile-wide asteroid that apparently wiped out the dinosaurs 65 million years ago — within our lifetimes or even our grandchildren’s lifetimes are really very small.”

How small? According to a report in Forbes, the European Space Agency’s Near Earth Object Coordination Centre maintains a list of more than 1,300 “near-Earth” objects with the potential of impacting our planet. Most of the ones likeliest to hit us are relatively small (less than 10 metres across), and unlikely to disrupt life on Earth. The biggest one on the radar — a 1.1 kilometre beast known as asteroid 1950 DA — has a one in 8,000 chance of making landfall…800 centuries from now.

Dillow did acknowledge that “unless we can figure out a way to stop it,” Earth will be hit by an asteroid big enough to cause some level of local or regional destruction — or a global climate catastrophe — at some point in the future. Luckily, there’s good news there, too.

Scientists are on top of it, maybe

If you’ve seen any of the many movies about what might happen if an object from space hits the planet, you know that scientists do monitor this stuff. Remember Cooke? He’s part of NASA’s Meteoroid Environment Office, and there are lots of other groups of scientists and decision-makers also watching the skies for any potentially hostile rocks, including the International Asteroid Warning Network and the Space Missions Planning Advisory Group, not to mention governments the world over.

These groups do more than watch, at least in theory. If a meteoroid larger than 50 metres is spotted on a collision course with Earth, for instance, the United States will attempt to deflect it by matter of official policy. Dillow pointed out there are quite a few ways our scientists have considered for deflecting an asteroid, from lobbing white paintballs at it to change its reflectivity, to using nuclear weapons to “nudge it a little off course.” (There are international treaties that bar the use of nukes in space, but presumably the people in charge would make a clutch game-time decision to disregard those in the event of our immanent doom.)

The most likely anti-space rock scenario involves using “kinetic impactors” to deflect the oncoming terror. In this scenario, unmanned spacecraft would be packed full of metal and slammed into the asteroid at thousands of miles an hour to slow its speed. NASA is currently testing this approach via the Double Asteroid Redirection Test (DART) mission, the first real-world attempt to change an asteroid’s motion in space through kinetic impact. The DART spacecraft will deliberately collide with an asteroid that poses no threat to Earth, just to see how it goes.

If you want to feel like you’re doing something about the threat of asteroids, you can learn how to find and report them yourself. It might give you something to occupy your brain space with other than your fears of a catastrophic apocalypse. Or give you more time to think about the next global pandemic. Whichever.