The Asteroids That Could KILL Us All and How Long It Would Take

<h4>

The Asteroids That Could Kill Us All and How Long It Would Take</h4>

Life on Earth has already suffered a number of mass extinctions throughout its history. The world-ending events of the past have brought everything from volcanic eruption to slow-build climate change to fundamental shifts in the makeup of our atmosphere. An asteroid strike, though, brings much more sudden death and destruction, as well as all of those other factors. So, could a rock from space one day trigger our next mass extinction? 

This is Unveiled and today we’re taking a closer look at the asteroids that could one day kill us all… and we’re exploring exactly how much of a warning we’ll get.

Though large asteroid strikes are a rare occurrence, smaller ones happen far more frequently. According to NASA, Earth is bombarded with an average of 100 tons of space dust on a daily basis, and small asteroids (which are still roughly the same size as small cars) enter Earth’s atmosphere every year. Thankfully, the vast majority of rocks like these burn up before they hit the ground… but, occasionally, our planet is pelted with something bigger. 

The amount of damage a larger asteroid could cause depends on a variety of factors including the speed and angle of impact. But were an asteroid with a width of, say, fifty feet to land in a rural and unpopulated area, it’s thought the force would still be enough to shatter windows and release light bright enough to cause instant sunburn. A rock the size of a house could detonate on Earth with as much power as a nuclear bomb. Meanwhile, asteroids the size of football fields impact on Earth roughly every 2,000 years. However, for something to truly threaten the entire planet, it has to have a diameter of at least half a mile. Fortunately, rocks this size ramming into us are exceptionally rare, but that’s not to say that the solar system as a whole doesn’t contain thousands of asteroids big enough to pose a problem. In fact, a width of half a mile is actually very small compared to some of what’s lurking in the Asteroid Belt; the rocks there can be as large as 550 miles across, and more. 

As far as we know, we’ve never been hit with anything quite that big, but arguably the most famous asteroid strike in history came via the Chicxulub Impactor some sixty-six million years ago. A fateful rock thought to have been more than six miles wide, it’s also held by many as the event which triggered the K-Pg mass extinction which wiped out the dinosaurs. There’s no real reason to expect another impact on this scale any time soon, but such monumental events do happen - and could theoretically happen at any moment were an asteroid to go unnoticed. 

Missing something that big, though… Does it ever really happen? Surprisingly, yes, it does. In the summer of 2019, for example, we had a reasonably close call with an asteroid named 2019 OK - a football-field-sized rock which flew right by Earth with little to no warning beforehand. 2019 OK came within 45,000 miles of our planet, meaning it was less than one-fifth the distance to the moon from us. Still a long way away, but cosmologically speaking uncomfortably nearby. In fact, it was the largest asteroid to pass by Earth in a century, and yet it was only spotted on the very same day that it flew past us. Say 2019 OK had veered just a fraction off course and headed towards Earth… It would have made an impact to devastate an area of at least 50 miles across. 

Generally speaking, NASA and the world’s other space agencies are on top of things, however, keeping track of thousands of asteroids flying through space at any given time. Sure, there are some that slip through, but for the most part we’re already well aware of the most threatening asteroids out there, and we’ve calculated the likelihood that they’ll ever cross our path. Prior warning; asteroid naming practices aren’t exactly what you’d call “creative”; the monikers don’t exactly roll off the tongue.

One of the most threatening to us is named “(85713) 1998 SS 49”. This particular asteroid is part of the Apollo group, a band that are all expected to pass close to Earth at multiple times in the future, with this one projected to also eventually pass closer than the moon. While it is only around one third the size of the Chicxulub Impactor that did for the dinosaurs, were it to veer off course and hit us then it would still inflict major damage. Interestingly, “(85713) 1998 SS 49” is also expected to pass by both Mars and Venus, making it a multi-planet threat. Although so far there’s no solid evidence that a collision will happen. 

It’s difficult to precisely track objects like these because of their low reflectivity and relatively small size compared to things like planets and moons. But, such rocks are also listed as PHAs (or, Potentially Hazardous Asteroids) for a reason; because researchers believe they have the potential to change direction to become even more threatening than they already are. And, no matter how tricky it is to keep rocks like these in our sights, scientists are doing everything they can not to lose them! 

Another listed as a PHA is 4179 Toutatis, one of the largest and most lethal objects currently expected to pass close by us. With a diameter of three miles, it’s more than big enough to end the large majority of life and trigger worldwide effects on our planet, if it strikes. Toutatis is especially notorious, though, because it has a highly eccentric orbit, meaning that it’s also one of the most unpredictable asteroids out there. It’s a frequent visitor to our particular region of the solar system, as well, having had various close encounters with Earth in the past. Including in 2012, when it sped within eighteen lunar distances of us. It’s currently projected to pass Earth again in 2069, but this time it will be twice as close. We should be comfortably safe… but if its orbit proves more chaotic than we think, then maybe not! 

The outright largest known asteroid with the potential to impact Earth is another prospect entirely. It’s named “(53319) 1999 JM 8” - and is a whopping 4.3 miles wide, making it only slightly smaller than our dinosaur killer of yesteryear. It’s another frequent flier around these parts, having passed within 0.2 astronomical units of Earth at least five times in the last century - with its next approach at a similar distance slated for 2075. JM 8 is also extremely dim, it has exceptionally low reflectivity and a chaotic orbital path, all of which makes it especially difficult to track through a telescope and therefore a likely candidate for one day passing by without our knowing. In the event that it eventually came close enough to smash into us… well, our world would be plunged into a wholly apocalyptic scenario, facing multiple extinctions and total ecological disruption. 

But - and this is important - not one of these asteroids is actually expected to hit Earth; rather, these are the ones scheduled to pass unusually close by. Right now, their orbits are subject to change, which is why they’re monitored as a potential threat. But that doesn’t mean that any of these rocks really will crash into us anytime soon. It’s just that if any of them did change course, defy predictions and make straight for us, then they’d all have the potential to trigger worldwide chaos. 

And, coming up next, we’ll take a closer look at exactly how much time we’d have on our hands if the worst ever were to happen.

Ever since we discovered in the 1980s that a monstrous asteroid wiped out the dinosaurs, we’ve been obsessed with the idea that the same thing could happen again. After all, the solar system contains hundreds of millions of asteroids, and it seems like at any moment one could tumble out of orbit and hurtle towards us. But how much time would we have to prepare if that happened?

How long would it take an asteroid to hit Earth?

No asteroid could ever destroy Earth, thankfully, because none of them are big enough to cause a planet-shattering impact. But many could wipe out life as we know it in the short term, much like the asteroid that killed the dinosaurs 66 million years ago. That asteroid, the Chicxulub Impactor, which landed on the coast of what is now Mexico’s Yucatan Peninsula, was only about 6 miles wide going by the size of the crater, which is frighteningly small considering just how many asteroids of this size or significantly bigger there are out there. And some of the potentially hazardous asteroids watched by NASA, in particular one called Apophis which has made headlines more than once for approaching Earth uncomfortably closely, is only 1,100 feet wide – that’s just 0.2 miles. NASA says there’s no danger of Apophis hitting us in the next 100 years, but it’s true that a large asteroid definitely will hit Earth again one day.

But where might this asteroid come from? Well, excluding objects from beyond the solar system, the absolute furthest point an asteroid could originate from is the Oort Cloud. The Oort Cloud is a theoretical sphere of planetesimals beyond even the heliosphere, surrounding the solar system like a shell of debris. Most long-period comets come from the Oort Cloud and can take thousands or even millions of years to complete their orbits around the sun. The Oort Cloud primarily contains ice and comets, but it does contain some heavy asteroids as well. The inner edge of the Oort Cloud is thought to begin anywhere between 2,000 and 50,000 astronomical units from the sun, and extend to between 100,000 and 200,000 astronomical units from the sun. One astronomical unit is the average distance between the sun and Earth, which is roughly 93 million miles. 200,000 astronomical units is over three lightyears away! So, how long would it take an asteroid coming from the outer edge of the Oort cloud to crash into us here on Earth?

Well, asteroids orbit the sun on average at around 15.5 miles per second, or 55,800 miles per hour. Since, again, 1 AU is 93 million miles, it would take an asteroid traveling at 55,800 miles an hour 1,666 hours or 69 days to go 1 AU. That means it would take 6.9 million days to travel from the edge of the Oort Cloud if it’s 100,000 AU away, or 18,891 years. If the edge of the Oort Cloud is 200,000 AU away, then doubling that number gets you the most extreme estimate: 37,782 years. That’s a very long time for us to prepare, and by that point, it’s easy to imagine humans could have died out from something else or even left Earth completely. At the nearest possible edge of the Oort Cloud, just 2,000 AU away, it would take a comparably fast 378 years. But that’s still plenty of time for us to develop a countermeasure. So, if an asteroid fell out of its orbit in the Oort Cloud today, and was traveling at an average speed, it would still take anywhere between 38,000 years and 380 years to reach Earth. Admittedly, it could travel faster or slower than this, though more likely faster if you account for how acceleration speeds up the closer an object is to the sun.

Far closer to us is the Kuiper Belt. Unlike the Oort Cloud, the Kuiper Belt – like the planets – orbits the sun on a relatively flat plane, rather than being a spherical cloud of celestial bodies. It’s also significantly closer, ranging between 30 and 1,000 AU from the sun. This means that at most, it’ll take 189 years for a Kuiper Belt asteroid to reach us, and at the shortest, less than 6 years. Considering the Kuiper Belt is beyond Neptune, that’s very worrying when we take a look at the solar system’s primary source of asteroids: the asteroid belt between Mars and Jupiter.

The asteroid belt is between 2.2 and 3.2 AU from the sun, making it 1.2 and 2.2 AU away from Earth on average. At the shortest, that’s about 83 days, and the longest, 152 days, or 5 months. That’s a lot more frightening than even the Kuiper Belt’s 6 years, which is starting to look like a very reasonable amount of time to prepare for an asteroid impact. We also need to take into consideration exactly where Earth is in its orbit relative to where the asteroid’s journey begins; for instance, if an asteroid 2.2 AU away from the sun begins to head towards us, it’s possible that when it crosses Earth’s orbit, Earth might be on the far side of the sun, an additional 2 AU away, and it would keep going straight into the sun. It’s also worth noting that Earth’s orbit is huge; each year, Earth travels 584 million miles, and more than 99.99% of Earth’s orbital path is empty at a given moment, which gives an asteroid millions of miles of leeway.

It’s been estimated that we’d need an asteroid with a diameter of 60 miles to completely wipe out life on Earth. But the Chicxulub Impactor was only 6 miles wide, so even a much smaller asteroid would do incredible damage to the planet. And unfortunately for us, there are lots of asteroids floating around large enough to do this – NASA estimates that there are as many as 1.9 million asteroids in the asteroid belt with a diameter larger than 0.6 miles. And bear in mind, once again, that the tabloids’ favorite deadly asteroid, Apophis, is three times smaller than NASA’s lower limit. The asteroid belt also has many objects that are hundreds of miles wide, including Ceres, the dwarf planet – though it’s not likely that Ceres is going to fall into the sun anytime soon, or even ever.

With so many asteroids out there, we will have another large impact one day, even if it’s not anytime soon, and we’ll need to be prepared when it happens. Luckily, not only are NASA and other space agencies tracking asteroids but there are lots of publicly funded non-profit projects aiming to fill in the gaps, like the Sentinel mission. Sentinel uses an infrared telescope and boasts many people who previously worked for NASA and prestigious colleges. Somebody will spot a world-destroying asteroid ahead of time. But one coming loose from the Kuiper Belt still wouldn’t give us much of a heads-up if it came straight for Earth.

Many scientists are working on predictions of what would happen if an asteroid hit and developing designs for countermeasures, but at the moment, the only realistic countermeasure that we could pull off in the shortest time span – 83 days – involves nuclear bombs. Blowing up a hazardous asteroid with enough nuclear weapons is the only asteroid countermeasure currently in our wheelhouse and that could be deployed in such a short amount of time. For once, Earth’s huge stockpiles of nuclear weapons will be beneficial; the world has, in total, close to 14,000, and since an asteroid impact would affect everybody it’s not hard to imagine the planet’s nuclear superpowers would work together to deal with the threat. We even already have plans for absolutely huge nuclear devices solely for the purpose of blasting a dangerous asteroid away. Other methods are more science-fiction, with many researchers actually advocating for the use of a gravity tractor. We haven’t yet developed any gravity tractors, which are large, artificial objects that would use their own gravitational field to redirect a problem asteroid, but with enough R&D they could become viable options.

Despite the vast distances in space, many of the asteroids close to Earth could find our planet worryingly quickly, and we don’t have much of a plan for when the inevitable happens.