What are the chances of an asteroid hitting earth in 2032?

Summary

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More or Less: Behind the Stats

Episode: What are the chances of an asteroid hitting earth in 2032?

Host: Tim Harford (BBC Radio 4)
Date: March 22, 2025

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Overview

This episode delves into the recent media storm around asteroid 2024 YR4, discovered in December 2024, and its potential to strike Earth in 2032. Host Tim Harford and NASA navigation engineer Davide Farnocchia break down the numbers, clarify why early predictions created alarm, and set the actual risk in scientific context—all while debunking fears stoked by sensational headlines.

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Key Discussion Points & Insights

1. Discovery of Asteroid 2024 YR4 & Media Frenzy

• [01:38] Tim Harford recounts how astronomers in Chile discovered a new asteroid (2024 YR4), sparking wild predictions in the media about its potential to hit Earth and the likely devastation.
• Social media amplified the panic, asking if the asteroid could destroy entire cities or countries.

2. Initial Risk Assessment & Escalating Probabilities

• [02:30] Tim reveals the initial odds:

  “The initial finding was a 1% likelihood of hitting Earth... shortly after discovery, this 1% likelihood was upgraded to 3%.”

• Only one recent asteroid approached this risk level; it failed to impact, as will a prominent near-Earth pass in 2029.

3. The Role of Asteroids in Earth’s History

• Recaps real asteroid impacts: Chelyabinsk (2013) and Tunguska (1908), both in Russia.
• Emphasizes how asteroid collisions have occasionally been catastrophic on a planetary scale, but most are far less dramatic.

4. Understanding Asteroids and Space Debris

• [03:41] Davide Farnocchia introduces his role:

  “My name is Davide Farnocchia. I work as a navigation engineer at NASA's Jet Propulsion Laboratory and I track asteroids and comets for my job.”

• [04:38] On how much material actually reaches Earth:

  “Space is mostly empty, but there is material. And Earth is reached by about 100 tons of interplanetary material pretty much any given day. ... Most of that is dust and so we don't even notice.”

• [04:59] Asteroids are described as leftovers from planet formation, mainly orbiting between Mars and Jupiter due to Jupiter’s gravity blocking a new planet from forming there.

5. How Asteroids Change Orbits & Approach Earth

• [05:39] Farnocchia uses the swing analogy for orbital resonance:

  “If you are in a resonance that your motion has the right timing compared to that of Jupiter or another planet, your orbit kind of gets excited and you might get injected into the inner solar system.”

• Small asteroids routinely enter our atmosphere and burn up; in 2024, four such harmless objects were detected.

6. Actual Impact Rates & Risks

• [06:46] Harford:

  “Scientists have used crater formation rates on the Moon to calculate that over the last 600 million years, the Earth has been struck by around 60 objects whose diameter was 5 km or more.”

• 2024 YR4 isn’t a planet killer; it's about 40–90 meters wide—big enough to devastate a city but not cause mass extinction.
• [07:40] Farnocchia provides the updated risk estimate:

  "Right now it's 5 in 10 million. Those are the odds. Very, very small.”

7. Why the Numbers Changed—And the Role of Uncertainty

• Early projections had less data, resulting in high uncertainty and seemingly alarming probabilities (up to 3.1%).
• [08:28] Farnocchia explains:

  “As we gathered additional observational data, this uncertainty in Position for The asteroid in 2032 became smaller, but the Earth remained inside the swath of possible positions for the asteroid. And so the probability went up because the Earth was occupying a larger fraction of that uncertainty.”

• Over time, as trajectory estimates improved, the likelihood dramatically fell.

8. The "Intersection" Analogy

• [08:59] Harford:

  “Think of it as kind of like an intersection, a road junction such as a crossroad. We know where the Earth is... we can’t predict exactly the asteroid. As the weeks have gone by, they've collected more data... and the likelihood of a collision has dropped.”

9. Current (Extremely Low) Odds and Ongoing Monitoring

• [09:32] Farnocchia:

  “It's 99.9999999. Whatever.”

• Harford: “It's not going to hit.”
• NASA continues constant surveillance of new asteroids for potential future threats.

10. Should We Be Worried?

• [10:04] Farnocchia reassures listeners:

  “Asteroid impacts for asteroids that are capable of causing substantial damage are really unlikely. It's not something that people should lose their sleep over.”

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Notable Quotes & Memorable Moments

• [02:30] Tim Harford: “A 1% chance of something really bad is still quite bad, but mostly because shortly after discovery, this 1% likelihood was upgraded to 3%.”
• [04:59] Davide Farnocchia: “Jupiter was pulling enough with its gravity to prevent the formation of another planet between Mars and Jupiter. And so we were left with a bunch of rocks in that ring...”
• [05:39] Davide Farnocchia: “It’s like what kids do when they go on a swing... if your motion has the right timing, your orbit kind of gets excited and you might get injected into the inner solar system.”
• [07:49] Tim Harford: “Very small indeed. So why did everyone get so excited?”
• [09:32] Davide Farnocchia (on current odds): “It's 99.9999999. Whatever.”
• [10:13] Tim Harford: “And with those words of reassurance, we leave you…”

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Important Timestamps

• [01:38] — Introduction and media panic over 2024 YR4
• [02:30] — Initial risk estimates and what these numbers mean
• [03:41] — NASA’s Davide Farnocchia on asteroid tracking
• [04:38] — Daily inflow of space material to Earth
• [05:39] — Explanation of orbital resonance and how asteroids enter the inner Solar System
• [07:40] — The actual (very low) probability of impact
• [08:28] — Why initial risk estimates rose before falling
• [08:59] — Intersection analogy clarifies findings
• [09:32] — Current odds: essentially no risk
• [10:04] — Should you be concerned? (No.)

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Tone and Language

The episode is factual, calm, and lightly humorous, with Harford’s trademark approachability and Farnocchia’s reassurances against media hype. Technical explanations are made accessible using vivid analogies (swings, crossroads) and down-to-earth language.

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Bottom line:
Although asteroid 2024 YR4 briefly made headlines with alarming-sounding risk percentages, more observations have reduced the likelihood of a 2032 impact to vanishingly small levels. NASA’s ongoing tracking systems mean future threats are closely monitored, but there’s no reason to lose sleep over city-sized asteroids—at least not this one.

Transcript

[Tim Harford]

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[Tim Harford]

Hello and thank you for downloading the More or less podcast with me, Tim Harford. We're the program that looks at the numbers in the news and in space. On December 27, 2024, when many of us were still in a mince pie coma, astronomers in Chile discovered an object in space with a trajectory that was potentially a bit too close for comfort. The object was an asteroid which they called 2024 yr4. Cute. As you probably know, asteroids are basically space boulders and quite probably dinosaur killers. News agencies and social media went wild trying to predict which cities it would hit and what the damage would be.

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There's a potential danger in space and it's on a collision course with city destroy asteroid that could smash into Earth.

[Davide Farnocchia]

In 20 seconds and wipe out an.

[Tim Harford]

Entire country in few seconds. People certainly lost their cool. So what was the likelihood of the asteroid actually hitting Earth? It must be a pretty high percentage to get people so excited. 1%. The initial finding was a 1% likelihood of hitting Earth. So why was this such a big deal? Partly because a 1% chance of something really bad is still quite bad but mostly because shortly after discovery, this 1% likelihood was upgraded to 3%. Only one other asteroid in recent times has come close to that. That one won't hit us. Don't worry. You should be able to see it pass harmlessly over in 2029. But sometimes asteroids do hit. For example, in 2013 when an asteroid hit Chelyabinsk, Russia or the tunguska event of 19o also in Russia. It seems asteroids really hate Russia. So what are the odds that asteroid 2024 yr 4 could give us a close encounter of a crashing into our planetary kind?

[Davide Farnocchia]

We have a lot of asteroids and comets in the solar system. We actually cataloged more than 1.4 million of those. Some of them have the potential of coming close to the Earth. My name is Davide Farnocchia. I work as a navigation engineer at NASA's Jet Propulsion Laboratory and I track asteroids and comets for my job.

[Tim Harford]

Asteroids are tracked using data gathered by astronomers around the globe. They look for the infrared signal of a nice warm asteroid or by light reflected off an asteroid's surface. They then calculate the speed by measuring how quickly they go past stars. As stars don't really move, they're a good reference point. Most of us are familiar with asteroids from disaster movies such as Armageddon, Deep Impact and Ice Age 5 collision course. Although we haven't had to tackle any Hollywood sized asteroids as of yet. Objects entering Earth from space aren't as uncommon as most of us would believe.

[Davide Farnocchia]

Space is mostly empty, but there is material. And Earth is reached by about 100 tons of interplanetary material pretty much any given day. That's the typical rate. But most of that is dust and so we don't even notice. It's too small to make any effect.

[Tim Harford]

Some of these objects include asteroids, which are among the oldest objects in the solar system.

[Davide Farnocchia]

They are kind of the leftovers of the formation process of the solar system. When the solar system formed, there was a lot of material going around. A lot of that material kind of got back together and formed the planets. But some of that material remained between the orbits of Mars and Jupiter. Jupiter was pulling enough with its gravity to prevent the formation of another planet between Mars and Jupiter. And so we were left with a bunch of rocks in that ring between Mars and Jupiter.

[Tim Harford]

Occasionally some of these asteroids escape this interplanetary ring road due to a mechanism called resonance, which is similar to what.

[Davide Farnocchia]

Kids do when they go on a swing, right if they're gonna swing and they move their legs with the right timing as the swing goes up and down they start going higher and higher. And so what happens is that if you are in a resonance that your motion has the right timing compared to that of Jupiter or another planet, your orbit kind of gets excited and you might get injected into the inner solar system.

[Tim Harford]

Having these intrepid little asteroids enter Earth's atmosphere isn't as rare as you might think. Smaller asteroids or fragments of asteroids measuring less than a meter across hit the Earth's atmosphere almost daily. Asteroids measuring a few meters across pass between the Earth and the Moon several times a month. Most don't actually enter into our skies, but some do.

[Davide Farnocchia]

We've had in 2024 four objects of a couple meters in size that were detected prior to reaching the Earth. And those were completely harmless. They burned up in the atmosphere. But it kind of prov concept that impacts are part of the evolution of the solar system or part of our experience in space.

[Tim Harford]

What about bigger asteroids? Thankfully they are a much rarer occurrence. We don't have much evidence for larger asteroids hitting Earth. But scientists have used crater formation rates on the Moon to calculate that over the last 600 million years, the Earth has been struck by by around 60 objects whose diameter was 5 km or more. That is 60 different occasions when quite a lot of the creatures on Earth at the time had a very bad day. 2024 yr 4 is not as big as this. Its diameter is thought to be between 40 and 90 metres, about the size of the Statue of Liberty, either with or without the plinth. The impact of an asteroid like this wouldn't cause mass extinction, but it could wipe out a city. So what are the odds of it actually hitting?

[Davide Farnocchia]

Right now it's 510 to the minus 7. So that would be 5 in 10 million. Those are the odds. Very, very small.

[Tim Harford]

Very small indeed. So why did everyone get so excited?

[Davide Farnocchia]

We actually had a much larger impact probability a while back. It reached a peak of 3.1% which is the largest impact probability ever recorded for an object of this size.

[Tim Harford]

3%. That sounds like time to get serious. But wait, that is still a 96.9% chance that it won't hit us. Still, I prefer the much longer odds we now have. So why is the collision now thought to be so much less likely? And why did the risk initially rise before it fell?

[Davide Farnocchia]

Initially we only had limited observational data. We saw that the impact in 2032 was a possibility, but the uncertainty was so large that the probability of actually hitting the Earth was very small. As we gathered additional observational data, this uncertainty in Position for The asteroid in 2032 became smaller, but the Earth remained inside the swath of possible positions for the asteroid. And so the probability went up because the Earth was occupying a larger fraction of that uncertainty.

[Tim Harford]

Think of it as kind of like an intersection, a road junction such as a crossroad. We know where the Earth is and how the Earth travels. We know at what time and what point the Earth will travel into the middle of the intersection. But we can't predict exactly the asteroid. As the weeks have gone by, they've collected more and more data, allowing them to more accurately measure the asteroid's speed, its path and the likelihood of a collision.

[Davide Farnocchia]

We realized that the object was going to go through it at a different time than the Earth.

[Tim Harford]

Excellent news. So what percentage are we at now?

[Davide Farnocchia]

It's 99.9999999. Whatever.

[Tim Harford]

It's not going to hit despite it very likely no longer being a threat. Davide and the team at NASA continue to watch 2024 yr4 and other asteroids.

[Davide Farnocchia]

So we track all of them every day. We have a bunch of objects that are discovered, those are new, they're added to the catalog and when that happens, we take a look right away and see whether they might be possible impact sometime into the future.

[Tim Harford]

With so many asteroids out there, is Davide worried about an imminent impact?

[Davide Farnocchia]

Asteroid impacts for asteroids that are capable of causing substantial damage are really unlikely. It's not something that people should lose their sleep over.

[Tim Harford]

And with those words of reassurance, we leave you thanks to Davide Farnochia and all the people at NASA who are keeping an eye on the skies. If you have any questions or comments, please do write in to us at more or less BBC.co.uk we will be back next week. Until then, goodbye.

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