TLDR: No, we are not all going to be wiped out by an asteroid in 2032!
I had a lot of fun yesterday talking to various BBC presenters about asteroid 2024 YR4 and the risk it poses (or not) to the Earth in 2032. The news that new projections of its orbital trajectory resulted in a higher risk that it will impact the Earth on December 22nd 2032, plus the fact that Director’s Discretionary Time has been granted on JWST to observe it, got a lot of people very excited. Is it time to call Bruce Willis and break out the nuclear bombs?!
Well no, of course not. The revised probability is 2.3%, or about 1 in 43. I’d take those odds on the lottery, quite frankly, but this isn’t going to lead to sleepless nights on the part of many astronomers.
As more observations are made of any asteroid with the potential to hit Earth in the future, as the trajectory is refined and the error circle gets smaller the probability goes up, and up, and up, until the circle no longer includes the Earth and the probability drops to zero. It happened with asteroid Apophis back in 2004 (remember that?), it’s normal.
There’s a lot we don’t know about this lump of rock just yet, such as its size (anywhere between 40 and 90 metres) and its composition, as well as its exact future trajectory, and it’s moving away from us getting fainter and more difficult to detect. We’ll find out more when it comes close again in 2028.
Even if it does impact in 2032, the effects would be localised – it’s big enough to destroy a city, but would be far less destructive than the impact that saw off the dinosaurs. It could still be a horrific disaster, but much bigger rocks have hit the Earth in the past.
Again though, it depends on parameters we currently don’t know very well. The size and composition matter, as do entry angle and speed. We can determine entry angle and speed from the trajectory, but the size, mass and composition are a bit more difficult, and are getting harder as it moves away from us, getting fainter and more difficult to see with each passing day.
If it is a sold lump of iron-rich rock, then it might create a crater similar to the famous Meteor Crater in Arizona, less than a mile in diameter. That would cause a lot of damage if it had the misfortune to land on an inhabited area, but luckily most of our planet’s surface isn’t inhabited. If it is more like the loose rubble piles that many asteroids appear to be, then we would likely see more of an airburst of the sort that was seen over Chelyabinsk in 2013, or in Tunguska back in 1908.
It’s reassuring to know that there is a planetary defence community, through organisations such as International Asteroid Warning Network and the Space Mission Planning Advisory Group, out there keeping an eye on things and making sure we are ready, just in case. And we’ve tested nudge techniques that could divert any potential impactor with the DART mission to Dimorphos just a few years ago.
I talked about all this with BBC 5 Live Breakfast yesterday morning, and then did a round of local radio stations in the afternoon, talking to presenters from Humberside to Guernsey about asteroids and planetary defence. Hopefully I reassured a few people!
Further reading
The International Asteroid Warning Network’s potential asteroid impact notification from January 29th, the point at which 2024 YR4 reached the threshold for further investigation.
February 2025 Newsletter talking about 2024 YR4 from ESA’s Near-Earth Object Coordination Centre. They currently have 1743 objects in the Risk List.
Latest updates from ESA on observations of 2024 YR4.
ESA’s Planetary Defence Office. (Yes, really.)
To see what sort of damage might be caused, you can simulate your own impact.
There are other ways to deal with potential threats, some more fanciful than others.
Orbital parameters of 2024 YR4 from NEODyS, and similarly data on 2024 YR4 from NASA’s Centre for Near-Earth Object Studies where 2024 YR4 tops the Sentry risk table, and data on 2024 YR4 from ESA’s Near-Earth Object Coordination Centre.
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