On Thursday, NASA announced that the risk of asteroid 2024 YR4 hitting the Earth had been recalculated thanks to additional data, and now has a 0.28 per cent chance of collision in 2032, or about 1 in 357.
This is a much better probability than several days ago, when the space rock was given a 3.1 per cent chance of striking Earth, or about 1 in 32. NASA expects the number to fall even further as more tracking data comes in.
Here’s what to know about asteroid 2024 YR4.
Why did the odds of a collision fall?
Dr. Paul W. Chodas, director of NASA’s Center for Near Earth Object Studies at the Jet Propulsion Laboratory in California, told the National Post it’s not because of any mistake made by astronomers.
“People say, ‘Oh, you were wrong the other day.’ No, it’s the data getting better and better, and the predictions getting finer and finer, and eventually we can rule out the impact. That’s the process and it has worked well.”
He adds: “Each asteroid, when first discovered, we don’t really know much about its orbit, and so we have to derive that by tracking it, and considering that asteroid orbits take many years, it takes some time before you’ve seen enough of the orbit before you can know it accurately.”
How big is 2024 YR4?
We’re not sure. “When they’re first discovered, they’re just points of light,” says Chodas. It could be as small as 35 metres across, or as large as 90 metres. Additional study will narrow that down as well.
What would happen if it struck Earth?
It would be bad, but it would not be catastrophic. Chodas says the asteroid that exploded over Chelyabinsk in Russia in 2013 was about 20 metres wide and produced an explosion of about 400 kilotons, equal to about 25 Hiroshima bombs.
“That sounds like a lot, but it’s high in the atmosphere,” he says. “It produces a blast wave. It broke a lot of windows, some walls and doors caved in, but really, very few casualties.”
If YR4 were twice the size of the Chelyabinsk asteroid, that would mean almost 10 times as much energy. It could flatten a city, were it to hit one. But Chodas says that a water impact might cause little to no damage. “It comes in so quickly that there’s really not a chance for a massive amount of water to be displaced that would cause a tsunami.”
How does this compare with the asteroid that wiped out the dinosaurs?
Not even close. That asteroid, called the Chicxulub impactor, hit what is now the Yucatan Peninsula in Mexico 66 million years ago. It’s estimated to have been 10 kilometres wide — bigger than Mount Everest.
Still, Heidi White, an astronomer and an outreach scientists with the Canadian Space Agency, says YR4 serves as “a good reminder of how important investing in tracking systems, investing in science and investing in monitoring is for protecting life on Earth. Because oftentimes we get so caught up in our daily existence that we forget that there’s a bunch of stuff out there that could potentially pose a threat. Humanity and Earth itself coexist in a much bigger cosmic ecosystem, and we need to never forget that.”
Are there other similar asteroids coming our way?
Yes, but none that currently pose a threat. Or at least, none we know of.
Chodas notes that the Spaceguard Survey began in 1998 with an aim of discovering and tracking 90 per cent or more of the near-Earth asteroids that are one kilometre wide or larger. There are estimated to be about 900 of those.
When that goal was complete, it moved on to looking for 90 per cent or more of the asteroids down to 140 metres in size. There are estimated to be about 24,000 of those, and roughly 45 per cent have been found, so the solar system surely has some surprises in store.
The good news is that an asteroid the size of YR4 is likely to hit Earth only once every few thousand years. And bigger asteroids, since there are fewer of them, are even less likely to come our way.
What could we do if an impact was imminent?
We could move people out of the way. Or we could move the asteroid out of the way. In 2022, NASA’s DART (Double Asteroid Redirect Test) mission smashed a small spacecraft into an asteroid to change its trajectory — just a little, but with enough notice a little would be enough.
“It was a very successful mission,” says White. “But there are other deflection type methods that are being proposed. Some include just nuking something, but that is, in my opinion, not the preferred path, because anytime you take a big thing and you bust it up, you’re going to create tons of debris. Some of it’s still quite dangerous. And then the trajectories of that debris you then have to track.”
But what if we really wanted to nuke something?
The 1998 science-fiction movie Armageddon, about a giant asteroid headed to Earth, imagined sending a crew of oil drillers to plant a nuclear bomb inside the asteroid, suggesting it’s easier to train drillers to be astronauts than it is to train astronauts to be drillers.
Enter Deniz Burnham, who joined the NASA 2021 Astronaut Candidate Class. She has a bachelor’s degree in chemical engineering from the University of California, a master’s degree in mechanical engineering from the University of Southern California, and — wait for it — is an experienced leader in the energy industry, having managed onsite drilling projects on oil rigs for over a decade, including in Alaska, Northern Alberta and Texas. If we ever decide on the Armageddon plan, Burnham will no doubt be first in line.
