Will I get hit by a meteor?

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1:39How many of you have gone out at night, into your back gardens or local parks or onto roofs, and looked up at the infinite mystery of space? When I was a very young boy, I had a telescope. The most interesting thing I saw was the rings of Saturn. I had seen pictures of it before. And I could see the shepherd mood too, which was great. You are listening to CrowdScience from the BBC World Service, the programme that launches itself into the infinity of science, fuelled by curiosity, on a mission to find answers to your questions. I'm Marnie Chesterton, and the voice you just heard is listener Scott.

2:21He may sound like he's speaking to us from space, but he's actually on a phone line from California in the US, where he's been keeping his eyes on the skies. Well, last month, a meteor crashed into the ocean off of the coast of the state of Massachusetts. And I was wondering, what kind of risk do we live under of getting taken out by a meteor? What's the likelihood of me getting hit by a meteor? That's my question. OK, tell me more about the meteor. How did people react to it at the time? Well, my friends back east, they heard a sonic boom and that was it. Were your friends back east genuinely concerned about getting hit?

3:04No, they didn't care at all. They just shrugged it off. New England is man. They were just like, ah. I reacted to it because I'm from Massachusetts, you see. And I left in 1992 and I thought, wow, I almost got hit. But it is one of those things. You know, if I want to avoid being hit by a tram, I won't go anywhere near the tram tracks. But if something comes from space and it's going to get me, there's nowhere to hide, really. Why didn't they see that one coming, man? That's what I want to know. OK. You want to know why we didn't see it coming, how many of them we don't see coming, and then do some maths.

3:44What chance is there that we might get struck by one? Yeah, exactly. I want to know. Am I going outside today or what? Thank you, Scott, for that cheery question. So, what are the chances that a space rock is going to come hurtling out of the sky with no warning and, in Scott's words, take you out? Could we predict when meteors are coming and maybe get out of the way? And in a world that seems to be getting more chaotic every day, is being hit by a meteor really something I need to be worrying about? First things first, I think we need to find out a little bit more about meteors. No, wait, meteoroids.

4:29Or is it meteorites? It is really confusing. Even for us working in this field, sometimes we get it wrong. So the current definition for these things is if you've got a rock in space, It can either be called an asteroid if it's rocky, or more of a comet if it's got icy material in it. But once you get to kind of smaller sizes and less than a metre, we call those meteoroids. A meteoroid is the rock out there flying through space. Like an asteroid, but under a metre in diameter. The optical phenomenon is what people see as a shooting star or meteor or fireball if it's really bright. The light show, basically, if you will.

5:06When a meteoroid passes through our atmosphere, it starts burning up and leaves a fiery trail behind it. That's when we call it a meteor. These things typically come at 15, 20 kilometres per second. An object that's a metre across will be as bright as the full moon, which is pretty cool to see. And then if it's the ground on the Earth, we call that meteorite. A meteorite is the rock once it's landed on the Earth and cooled down and hopefully been picked up by a scientist. So yeah, lots of terminology, confusing even for us. A scientist like this one, perhaps. Right, so I'm Dr. Hadrian de Villepoix.

5:47I'm originally from France and moved over to Australia to join a programme called the Desert Fireball Network. I've become the lead scientist of this fireball observation programme in Australia. Desert Fireball Network is a brilliant name, can I just say. So you're lead scientist of Desert Fireball Network. What does that entail? So the idea behind this observation programme is we've got these cameras looking up out in the outback in the network configuration, constantly taking pictures until we record one of those fireballs. The Desert Fireball Network doesn't just record the meteors as they streak a flaming path through our atmosphere.

6:27They use their cameras to triangulate the path each takes, predict where it might land, and then get out there to try and find it and bring it home for science. Oh, so that's the fun part of the job. So if meteorites survive, then we make predictions about where they fall. We can usually do that to a couple of square kilometres kind of uncertainty, but finding it is still a big challenge. A couple of square kilometres, trying to find something the size of a tennis ball, does sound like quite an advanced game of hide and seek. Yeah, or needle and a haystack, if you will. We don't always find them.

7:02You need a team of like six people looking like for days or maybe a week or two weeks to cover that whole area. So tell me about finding the treasure. What is it like? Oh, it's hard to describe. It's also hard to believe. We're actually doing some scouting of a site with a colleague of mine back in Australia before the main team was going to search. We were just having a look around. It's like, what does the ground look like? Is there lots of vegetation that's going to get in the way? Not hoping to find anything. And then we basically nearly stepped onto this rock. And looking at it to me, it was clear that it was a very convincing meteorite.

7:42But at that point, I thought my friend, my colleague had planted it there for us to find as a joke. So I did not believe him. He had the same suspicion about me. So we're in that funny thing for like a couple of minutes. It's like, are you tricking me? That's great. It turns out it was the rock we were after. And it's just incredible. Do we know how many meteors hit our planet on a daily basis? So meteors that people might be able to see, we get millions of those. But the bigger you go in size, the less frequent they are. And that's a real good thing. because once you get to like multi-kilometre sized objects, thank God they're not very frequent.

8:21Okay, and you are looking for meteorites. How much advance warning do you get? We get no warning. We basically know about them once they hit our atmosphere, so about 100 kilometres up. That's when they start making a light show. But while they're out in space to detect 10 centimetre cross meteoroids, you need a really, really big telescope. so most of them like we just don't detect we get zero warning until they hit our atmosphere oh wow and then how much time have you got between them hitting the atmosphere and them potentially hitting the ground the maximum warning you would be able to get is a couple minutes so there are millions of meteors hitting our atmosphere every single day they're too small to see them coming and once we do see them they'll hit the ground in mere minutes so far it's sounding like Scott could get a direct hit at any moment.

9:15But there's a twist. Not all meteors produce a meteorite. The vast majority of them just burn up completely or explode when they hit the atmosphere and fall as dust. Those aren't going to take anyone out. Phew. It's not just size, it also comes down to strength. If you've got a rock that's light and fluffy, not really well bound together, it will break up pretty quickly when it hits the atmosphere. whereas if you got say like a pure iron asteroids that impacts like this one's got much higher chance of surviving in one piece to the ground for example. Hadrian looks for the meteors which fall out in the barren Australian desert and there's not much chance of them harming anyone out there.

9:58Most of the earth's surface around 71 % in fact is ocean and the ones that fall out there are unlikely to hurt anyone either although one could knock out an unsuspecting fish I suppose. But of course, they do fall on human habitats as well. We've had several cases of meteorites going through roofs. Sometimes the easiest way of finding them is somebody reporting that they got a hole in their roof and a weird rock that's landed in their living room. It sounds unlikely, but actually this happened quite a few times. Bad news, Scott. Staying at home is not a foolproof strategy when it comes to avoiding meteors.

10:36The only known person in history to be hit by a meteorite was Ann Hodges. It happened in November 1954 in Alabama in the US. It was a big one too, about the size of a coconut. It left a three foot wide hole in her roof. Yeah, so I think what happened is the meteorite actually bounced off something else and then hit her on the leg. She got a pretty bad bruise. But we haven't had any recorded cases of people getting killed by meteorites. Our listener Scott wants to know what the chances are of being hit by a falling meteor. Is there any way of calculating that? I mean, how much risk do meteors pose to the average person during their lifetime?

11:20Yeah, that's an interesting question. So I run some numbers. We got some statistics on basically how often you get a meteorite big enough to survive atmospheric country and very rough back of the hand sort of calculation. If I was to estimate like what's the chance of you over the next year getting hit by one of these things, yeah, somewhere around one in a trillion. So really not a lot, definitely not something to worry about. The ones that you study are mostly fairly small, what centimetres, tens of centimetres. What happens, Hadrian, when larger rocks head our way. So what size does a space rock stop being an interesting scientific specimen and stop becoming something that might destroy a city?

12:05Yeah, what size does it become a problem? That size is around 10 metres. You've got an asteroid that's around 10 metres, punching for atmosphere at high speeds. It creates a shockwave. That shockwave is what does a lot of the damage. And that happened last time in Russia in 2013. So the Chelyminsk fireball over like central Russia. Ah, yes, I remember watching the dashcam footage. Yeah, it was a pretty impressive fireball, wasn't it? And the fireball was brighter than the sun as well, which was crazy. But that didn't hurt anyone. What really hurt people is a couple minutes later, once you got that giant sonic boom, creating like an overpressure and breaking windows and the broken glass is what hurt people.

12:47A lot of people. The Chelyabinsk meteor left 1 ,491 people with injuries serious enough to seek medical treatment, most of them from flying broken glass. Luckily, it didn't kill anyone on that occasion, but basically 10 metres is when things start getting dangerous. We're still working out the statistics on those objects, but something around the 20 metre size at Shell Bains, maybe once every 50 years. And as you get towards 50 metre size range, like maybe every 100 or 200 years. But those events are so rare, and they've been so rarely recorded by instruments that it's really hard to put tight air bars on how often they happen.

13:27Okay, so there's millions of meteors arriving every day, but very few of them survive all the way down to the Earth's surface, where they could smack you on the head. And when you factor in how much of our planet is uninhabited, the chances of one hitting you are really very small, one in a trillion, if Hadrian's very rough back-of-the-envelope calculation is to be believed. So far, Scott, I think you're safe. But meteors aren't the only things that might be hurtling through the cosmos on a beeline for our pale blue planet. There are some much bigger and scarier things out there. The meteoroid's big brother.

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15:18You're listening to CrowdScience from the BBC World Service. I'm Marnie Chesterton and I'm trying to answer a question from Scott in California. What's the risk of being hit by something plummeting to Earth from space? And if you thought a space rock the size of a washing machine was scary, how about one the size of a 15-storey tower block? Earlier in 2025, we were faced with an asteroid that was estimated ultimately to be about 60 metres in size. A terrifying threat with a less than terrifying scientific name. 2024 YR4. 2024 YR4 was discovered at the end of 2024 and by early 25, where it could be in 2032 intersected the Earth.

16:09This is the disaster scenario Hollywood dreams of. A massive asteroid zooming through space on its enormous four-year-long elliptical orbit around the Sun, but this time on a collision course with our planet. Well, kind of. Scientists' predictions indicate it was heading for our neighbourhood at least. To know if it would hit us, they need more data. It also went way, way off the Earth. It could have been anywhere around there. But for the first time in about two decades, this was an asteroid approaching a 1 % chance of impact in the future. It sounds low, but in our world, something that could do damage reaching that level was very significant.

16:51And as we got observations every night from the World Wide Network of Telescopes, the probability of impact in 2032 continued to rise. Kelly Fost is part of a team that detects massive asteroids out there in space and checks for the possibility of a direct hit on Earth. We weren't frightened because we knew that there was a high likelihood that eventually the impact probability would drop. but we took it very seriously. To be honest, when I spoke to the chief scientist of the Desert Fireball Network earlier in the program, I thought that that was going to be the coolest job title we were going to get.

17:33Kelly has just raised the stakes. My name is Kelly Fast. I am the acting planetary defence officer at NASA headquarters in Washington, D.C. I lead NASA's Planetary Defence Coordination Office. Planetary defence officer. Is that the best job title you've ever had? Absolutely, absolutely. It's a heavy responsibility, but it is fun to have a cool title to go with it. Back to that asteroid, 2024 YR4, hurtling our way and that 1 % chance of impact. Kelly and her team watched and waited for more data to come in. We've done exercises with hypothetical asteroids that could impact at some future date. All that's been very valuable, but to actually live it for real, I wouldn't say it was scary, but it was sobering.

18:27And ultimately, over time, we were able to get enough observations and be able to say, it's going to pass by the Earth. It's not going to be a problem. And that was a great test of the system to be able to retire a threat like that. Right. So yes, you are a defence officer, not just for the US, but on a planetary scale. So what does that entail? Well, here in the United States, NASA has the Planetary Defence Coordination Office taking the lead on finding asteroids and tracking them and getting them in the catalogue and looking to see if any pose an impact threat. Asteroids in our solar system are, like Earth, on an orbit around our sun.

19:06But they're not as neat as our nice, even, mostly circular orbit. They zoom way out wide and then back in tight on an elliptical orbit, which means there's a chance their route could overlap with ours. You can't just spot an asteroid once and then know where it's going to be in the future. You have to get multiple observations as it moves across the sky to be able to tell you, 10, 20, 100 years into the future, is it going to be in the same place at the same time as the Earth? And what kind of objects that might come close to the Earth are you interested in defending us from? We have a metric to find the asteroids that are estimated to be about 140 metres and larger in size.

19:53Unlike the smaller meteoroids, like the ones Hadrian is scanning the skies for, or the ones Scott saw on the news, asteroids of this size are visible out in space. They're so big that they reflect sunlight as they hurtle through the dark so telescopes can pick them up. Everything Kelly and her team find gets logged in the catalogue. We catalogue anything we find because asteroids smaller than that could pose a threat. We're finding asteroids of all sizes, getting them into the catalogue and then being able to check them off and say, OK, that is not the asteroid we're worried about. Let's keep looking.

20:32So do we know where all the dangerous asteroids are? If you talk about like the one kilometer and larger asteroids, you know, something that could have global effects or they like to talk about the dinosaurs with those. The nice thing is we're not finding many of those at all every year, maybe one or two. Those are the planet killers, right? Yeah, some people say that. And the nice thing is, we're not so worried about that because we know that population pretty well. So let's now look at the ones that could, we're maybe not so much worried about global consequences, but what about regional consequences?

21:05And so that's this size range, 140 meters and larger. That is estimated to be about 25 ,000. We have about 46 % of those, but there is still a ways to go. So how often do asteroids large enough to cause regional damage actually hit the Earth? That's like a one in 5 ,000 year event. So, I mean, we are talking very infrequent. As you go larger in size, it would be even less frequent as you went up to like the 140 meter in size or larger than you get to tens of thousands or millions of years even for these really large ones. you know space is big for the earth and an asteroid to come into the same place at the same time it's a rare event we are talking about something that might not happen in our careers or lifetimes or for thousands of years or or next week we're not sure with these bigger asteroids although the chances of being hit are still minuscule there are a lot more ways of meeting your end if it does happen.

22:11Not just flattening by the rock itself, but crushed by the energy pulse it would release as it hits the atmosphere, or sliced apart by flying glass as the sonic boom shatters windows. Trees or buildings could be levelled, if one falls into the sea there could be a tsunami, and there could be knock-on effects in the weeks or months afterwards, dust particles in the atmosphere or climate disruption. So what do we do if one is heading our way? Well, as you might expect, the Planetary Defence Coordination Office is ready to do some planet defending. We do fund teams who look at deflection techniques.

22:53Gravity tractor, what if you positioned the spacecraft as a mass next to an asteroid and you had lots of time to just sort of tug it with gravity? ion beam deflection, where you use like an ion engine on your spacecraft, firing ions at the asteroid in these slow push techniques. We even collaborate with the US National Laboratories here on modelling what Hollywood likes to go to, you know, a nuclear deflection option. Okay, so you've got kinetic impactors, so fire things at it, or you've got gravity tractors, So use gravity to try and pull it to a different course. And you've got nuclear to blow it up.

23:32Or to deflect it, yes. And it really, all of it, it does depend on the asteroid because you might want to say, OK, that's a rubbly asteroid that we want to be careful how we deflect it so we don't break it into multiple pieces. Those are all important questions. And honestly, all of that really does depend on the asteroid. And this work isn't just in the hypothetical realm. In 2021, NASA sent an actual unmanned spacecraft to an actual asteroid, well, a small moonlet orbiting an asteroid, smashed into it at around 14 ,000 miles per hour and successfully knocked it very slightly off course. This wasn't an asteroid heading for Earth, just a test of the technology.

24:18But it worked. It was called the Double Asteroid Redirection Test, or DART. With the DART mission, NASA was hoping to actually test a deflection technique, the kinetic impact technique. That's a technical way of hitting it really hard. Yeah, right. That's a way of saying you want to hit an asteroid with your spacecraft. Very expensive spacecraft, but it's for a good cause, yes. And so NASA's goal was to, first of all, test the technique. Like, can we even hit an asteroid? But then to actually measure what the deflection was. And so that actually showed us we can actually change the path of an object in space.