Could an asteroid hit the earth in 2032?
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Imagine a massive asteroid hurtling towards Earth, about to smash into us and wipe out all living things. The end of humanity as we know it.

OK, don't panic just yet. There is an asteroid heading our way. It's called Asteroid 2024 YR4. But the chances of it hitting us are slim. Scientists first said it was around 3%. Now it is much, much lower. Yet the headlines are still calling it a city killer and warning of Armageddon. So should we really be worried? What happens when an asteroid does hit? And could we stop it?

That is what we're exploring on this episode of What in the World from the BBC World Service. I'm Hannah Gelbart. Let's find out more about this now from Georgina Ranad, the BBC science reporter. Hi. Hello. So to start off, let's go back to basics. What is an asteroid? Absolutely. I think we do have to go back to basics on this one. So asteroids are chunks of rock of lots of different sizes moving around in space and

They are left over from when our solar system formed around 4.6 billion years ago and that was obviously this really fiery, chaotic time when rocks and materials smashing into each other and it formed our planets and these asteroids are left over from then. They range in size so the largest by far is about 530 kilometres across, so it's huge, but most are smaller and some as small as 10 metres across.

And many of them are in this place called the asteroid belt, which is between Mars and Jupiter planets that orbiting the sun. And occasionally some of them are pulled out of that belt by the gravity of other planets. And that's when they come near Earth. Everyone has been talking about this asteroid in particular, 2024 YR4. What does it look like and where did it come from?

So I do want to say what a media star this asteroid has been. It's been everywhere. I've seen so many memes and some quite outlandish headlines about it. But it's basically a rock, as I said. It's between 40 and 90 meters across. They're still not quite sure how big it is.

It was first detected in December by astronomers in Chile, and then it set off warning systems because when astronomers calculated its trajectory, where it might go next, they said it had a 1.2% chance of hitting Earth, and that actually rose to about 3%.

And then we had all these headlines. So it was called a city killer, a chilling asteroid. Some were saying it could be the end of the world. Some media were trying to say which city it might hit. A lot of that was somewhat overblown. So for several weeks, it did look like there was a chance that it would hit Earth. So two UN groups were activated. They have these amazing names. One is called Space Mission Planning Advisory Group. Yeah.

There are people who say their job is planetary defense. It's just kind of amazing titles. But basically they meet to discuss the asteroid trajectory and how they could plan for a possible impact on

It was rated on, there's a hazard scale to rate how dangerous an asteroid might be. That was three out of 10. I mean, all the language is a bit scary. So that means a close encounter that warrants attention. Because 10 out of 10 is the end of the world, right? Well, probably. Or yeah, we'll definitely notice if that happens. But yeah, then even if it did hit,

the chances of it hitting a populated area where humans live was quite small. It was more likely to drop into oceans on this path that the astronomers predicted. And even then, that risk has been going down. And actually now the chance has dropped to just 0.004%.

So it's really quite small. And it is normal for these predictions to go like that. So the risk goes up as astronomers reduce the area in which they think it could transit through. It's quite complex mathematics. And it wouldn't be any time in the near future, would it?

Well, there was a chance it was in 2028 or 2032. So it wouldn't have been this year, but it would have been really quite soon and actually so soon that some of the planetary defence systems that they've developed may not have had time to kick into effect. And where did the asteroid get its name, 2024 YR4?

So it's actually quite a boring answer. It's a naming convention. So basically 2024 because it was found last year in 2024. And YR4 is a naming convention. So YR is a code for the time of year and 4 just because it was found near the end of that year. So in December.

Tell me a little bit more about planetary defence and the plans that they have to intercept it. Like, are we talking lasers that can be fired to break up the rock or like ways it could be nudged off its course? What does planetary defence look like?

Yeah, so as you just said, it does sound quite sci-fi, but it is a serious area of work because although the chances are small, if a large asteroid did hit Earth, it could have really, really serious effects. And the idea is that it's better to plan for that rather than just let it happen. Some astronomers talk about a parallel with COVID-19. So the chances of a pandemic were low, but when it happened, obviously it had really serious impact. So the idea is all about preparation.

So right now there are no plans to intercept Y04 because we don't think it's very unlikely now that it's going to hit Earth. But they do have these technologies which are actually really recent. They're kind of these new, stunning, kind of nascent technologies. So one is called DART or Double Asteroid Redirection Test. Great acronyms. NASA have tested one. The US Space Agency have tested that one and found that it can nudge an asteroid off course.

So in 2022, they deflected an asteroid called Dimorphos around double the size of the one of YR4. And they did that by hitting it, again, sounds so sci-fi, but they hit it head on with a spacecraft that was about the size of a fridge. That took place 7 million miles from Earth. The craft drove into the asteroid at 14,000 miles an hour and it managed that deflection, nudged it off course and changed the orbit.

It sounds pretty incredible. I was reading that actually it's more likely that this asteroid YR4 might hit the moon. What would that mean? Yeah, so as the chances of it hitting Earth went down, the chances of it hitting the moon went up. And the scientists I was talking to were actually really excited by this. You know, the reality is that an asteroid hitting an object, hitting the moon or Earth, is a really amazing opportunity for scientists to study it because a lot of their...

their modelling, a lot of their work is based on calculations and theory. So it basically would, you know, what would happen is a large rock would hit the hard surface at high speed and you can imagine it would disrupt all that material. But it would give scientists this chance to study exactly how that worked and that would be a parallel for how it might happen on Earth. So we don't know if it's going to hit the moon, but if it does, I think there'll be some excited scientists. When asteroids have hit objects before, like

the Earth, which, you know, we know about the big one, the one that wiped out the dinosaurs. When else have asteroids hit the Earth and what happened then? Yeah, so it's really common for small asteroids or rocks to come into Earth's orbit and

But we're lucky on Earth compared to most of the planets that we have an atmosphere. And that burns up rocks when they stray into our path. So actually, if you ever see a shooting star up in the night sky, there's a good chance that that is an asteroid, a small asteroid, burning up as it passes through our atmosphere. But a lot of small ones do hit Earth, actually. That's usually in the oceans, which make up 70% of the Earth's surface. Or they hit remote places.

So there are at least 50,000 that have been found in Antarctica. But actually, we don't really know how many hits or near misses we've ever had.

Because for most of our history as humans, we haven't been able to see them. We haven't had the technology to track them. So it's sort of been happening over our heads and we've had no idea. It's only really in about the last 30 years that this type of observation has been possible. And when there have been hits in the past, have we made any amazing scientific discoveries from them? Like, have we learned cool stuff from them?

Absolutely. So I think asteroids are amazing. They're kind of a portal to the rest of the solar system. They're a great way of seeing what's going on out there. They have material from other parts of the solar system or they come from other planets. So there's a really famous one which has, again, another acronym name, ALH84001. They think that came from Mars and so it has ever

evidence from that planet, minerals that tell us about the planet's history. We're always trying to learn more about the history of these, the other planets. And that asteroid had evidence that said that Mars may have had water on its surface billions of years ago. And that just helps us build up a picture of Mars.

But I also did a story a few months ago, which I found fascinating, but was about they found evidence of a huge asteroid that hit Earth when our planet was quite young. And they think it caused a tsunami bigger than any other known in history and boiled the oceans. They think it was 200 times the one that killed the dinosaurs.

But they also think that it helped early life thrive because it churned up all these minerals when life was still quite young and basic. And all these minerals and nutrients acted like a fertilizer on early Earth. So, yeah, I think, you know, not all asteroids are bad, basically. We can owe them quite a lot. 200 times the size of the one that killed the dinosaurs. I'm sure a lot of people have watched the Disney film Dinosaur. I loved it.

If people listening to this haven't, can you just give us a kind of potted history of what happened to the dinosaurs when the asteroid hit? Well, yeah, this is the one we all think of because obviously it had this huge impact on our planet. It altered its history. So the asteroid was much bigger than most of the ones I've just talked about, way bigger than YR4, about 10 to 15 kilometres across. And then that hit Earth about 66 million years ago.

And they think that about 75% of Earth's animals, including dinosaurs, died quite suddenly at that point. It hit at massive velocity, really fast and vaporized and then made this huge crater. But it also created a blast wave that

travelled across Earth and threw up all this material, rock and dust into the atmosphere. So really a completely devastating day. And we know that it caused the extinction of this species that had been on Earth for, I think, 170 million years. So, you know, I just said not all asteroids are bad, but this one was pretty bad for these creatures.

Given what you've just explained, some people might be feeling a bit anxious about YR4. What kind of reassurance can we offer? Absolutely. So the chance now of it hitting Earth is really, really tiny, even when it was at 3%. So a higher chance of an asteroid hitting than in the past 20 years.

it was really small that it would have hit a populated area. So it was much more likely it would have hit the ocean, caused a few large waves in that area, but nothing like a tsunami. And of course, it does happen all the time. We have small fragments coming from the solar system and hitting our surface all the time.

And, you know, we have our planetary defence teams. They do exercises all the time. There's one in May when all these scientists will get together and plan out for a scenario where an asteroid would hit. So there's definitely a lot of work going on to protect us. But as I said, they really don't think it's this one, YR4, is going to hit us. Georgina, thank you so much for coming on the podcast. Thank you, Hannah. Great to talk to you. You too. Thank you.

That is it for today's episode. If you want to hear about other space stuff, we did an episode on space junk and how people are trying to get rid of it. You can find that wherever you get your podcasts and it's also on the BBC World Service YouTube channel. Just subscribe to our playlist. I'm Hannah Gelbart. This is What's in the World from the BBC World Service and we'll see you next time. Bye.