At least, that’s what’s most likely to happen. But based on the current crop of observations, NASA’s Center for Near Earth Object Studies, or CNEOS — whose scientists keep watch over all known near-Earth asteroids and comets — estimates that there is a 1.9 percent chance of that space rock smashing into Earth that day.

Here's another way of thinking about that. Imagine you have 53 buttons in front of you, and you’re asked to press one of them. Fifty-two of those buttons will result in that asteroid — dubbed 2024 YR4 — safely flying past the planet. But one of them will cause it to plunge into our atmosphere and hit a random spot on Earth. That could be the middle of a desert, or in the ocean, and the impact — although dramatic — will harm nobody. But if it hits a town or city, it will handily destroy much of it.

Editor's note: The odds keep changing so we'll keep updating the numbers. (Feb. 9th)

2.4% chance of Earth impact

1 in 42 odds of impact

97.6% chance the asteroid will miss the Earth

At this point, you’re probably wondering how you should feel about this. I don’t think you should be concerned; the odds of an impact remain low, and when more observations come in, it’s probable that the impact odds will plummet to a zero as the orbit of the asteroid is more precisely defined.

But I can’t tell you not to worry, so instead, I’m going to tell you what will happen next — what astronomers and planetary defenders are doing right now to protect the planet. I hope that knowing that practical steps are being taken to make sure we’re fully prepared for the worst-case scenario will assuage some of your anxieties.

First off, while tracking 2024 YR4 to accurately plot out its orbit, astronomers are scrambling to get a better estimate of the asteroid’s size. At the moment, they don’t know if it’s 130 feet long or 330 feet long. That may not sound like a big difference, but in terms of its potential to cause harm, it’s a vast gulf. In crude terms, an asteroid that doubles in size brings eight times more kinetic energy with it when it slams into the atmosphere.

Here’s an example. An asteroid 60 feet across will crash into Earth’s atmosphere, decelerate dramatically, and explode in mid-air, unleashing an explosion equivalent to a small nuclear weapon. It won’t make a crater, it won’t even make a fireball, but the blast wave will slam into the ground and cause widespread damage to buildings. Now double that asteroid’s size. At 120 feet across, the rocky missile still won’t make it to the ground, nor will it carve out a crater, but the blast wave will be comparable to one produced by a far larger nuclear weapon. Structures can be knocked down, people can be blown off their feet, and anyone in the blast radius stands a good chance of dying.

Knowing whether 2024 YR4 is 130 feet or 330 feet, then, is of paramount importance. The problem is that optical astronomy, which relies on reflected sunlight, only gives you a range of sizes. An asteroid that has a very shiny coating will reflect more light; one that has a dull coating reflects very little. Astronomers don’t know what the surface of 2024 YR4 is like, which means they can’t tell if it’s a 330-foot asteroid with a dull coating or a 130-foot rock with a shiny coating.

It's not clear when this size range will shrink. But planetary defenders have approval to point the largest telescopes with the best scopes at 2024 YR4 over the next few months, meaning they’ll have observations of it until early April — which, hopefully, will refine its size range somewhat and, more importantly, understand its orbit enough to drop that impact probability to zero.

But what happens if the odds remain above 1 percent? That’s where things get interesting, and almost entirely novel. As the asteroid is of a hazardous size, a possible impact is less than a decade away, and the odds of that impact are at least 1 percent, some planetary defense procedures have been activated for the very first time.

Planetary defense is, unsurprisingly, an international security concern. Within the United Nations is the Office for Outer Space Affairs (UNOOSA), which, you know, discusses all sorts of off-world shenanigans, from space debris to planetary defense. And nested within UNOOSA is the Space Mission Planning Advisory Group, or SMPAG, which was formed in 2014. Consisting of states with space agencies, the purpose of SMPAG is to come up with a way to communicate to the world the dangers posed by any sketchy-looking near-Earth asteroids — and to provide options for the planet to defend itself. They have never had to do this before, because an asteroid like 2024 YR4 doesn’t come around very often. 

For some time, America was the clear leader in the field of planetary defense. But today, multiple spacefaring nations are throwing their hat into the ring; the European nations making up ESA (as well as having their own asteroid-spotting telescopes) were participants in NASA’s asteroid-deflecting DART mission in 2022, and they are now flying their own spacecraft to investigate the asteroid NASA punched. China is also keen to showcase its anti-asteroid technology, India is getting better at navigating space by the year, and Japan has conducted several successful asteroid-burgling missions. That means 2024 YR4 will be on the minds of all these countries, along with several others.

What would actually happen should 2024 YR4 prove to be a clear threat to the planet is anyone’s guess. It depends on how cooperative, or not, various spacefaring nations will be, as well as the global security situation at the time. But let’s say that additional observations of this asteroid cause its impact odds to rise rather than fall.

One option would be to hit 2024 YR4 with a DART-like spacecraft, something known as a kinetic impactor. Smash into it at the right angle, with the right amount of force, and you can deflect the asteroid — and, just maybe, knock it out of Earth’s way.

The problem, though, is that the potential impact date is just under eight years out. That’s not much time to carefully plan out a deflection campaign. I imagine that a deflector spacecraft and launch vehicle, based on DART’s design, could be manufactured rather quickly, probably with the help of SpaceX (a participant in the DART mission). But you need to make sure that you conduct a near-perfect mission. If you hit the asteroid too hard, you could accidentally break it up into smaller, but still dangerous, shards — some of which may still strike the planet. And if you deflect the asteroid incorrectly, or insufficiently, it could still hit Earth, just not where it was originally going to strike.

Although it’s never been tested in space, space agencies may opt to use a nuclear explosive device, or NED. NEDs can give an asteroid far more of a push than just one DART-like impactor. A lot of work involving laboratory experiments and super-sophisticated multi-physics codes strongly suggests a NED can give an asteroid similar in size to 2024 YR4 a potent swat. And a recent study concluded that a 330-foot asteroid — the largest 2024 YR4 may be — can be essentially vaporized with a one-megaton NED if it’s met no less than two months prior to its impact day.

But, as you’d imagine, space agencies racing to launch nukes into space — even if it’s to try to save the world — carries a lot of risks, from the geopolitical to the most basic health and safety ones; you don’t want a nuke-armed rocket to explode in-atmosphere. And a NED mission isn’t guaranteed to work either. If you nuke the asteroid, and fail to deflect or destroy it, then you’ve now created a radioactive Earthbound asteroid, which nobody loves.

Another option would be to just take the hit. It’s difficult to imagine the world doing nothing whatsoever to try and prevent the impact, but if that asteroid is fated to reach terra firma, then the country in the firing line may try to evacuate people from the future, roughly city-size ground zero. The problem is that we don’t yet know where on Earth the impact will happen because the orbit hasn’t been comprehensively nailed down just yet. 

At the moment, the risk corridor — a line of possible impact sites — stretches across parts of India, sub-Saharan Africa, the middle of the Atlantic Ocean and the northern part of South America. Far more observations are required to refine this. Ideally, planetary defenders would ping the asteroid with radar, which is the best way to measure its orbit. But it’s not clear if that will be possible even when 2024 YR4 makes another close Earth flyby in 2028.

So, yes, there’s a lot of uncertainty. But what you need to know is that people whose job it is to literally defend the planet are tirelessly working to reduce that uncertainty. NASA and ESA are rallying the world’s astronomers to track 2024 YR4. And SMPAG is meeting in early February in Vienna to discuss the problematic asteroid. It’s not yet known what may result from that gathering, but its attendees will no doubt begin to share ideas about how to communicate the potential risks of this asteroid to the public and to policymakers — and they may talk about the various ways in which spacefaring nations could, if needed, stop an impact in 2032.

For now, try to relax. Above all else, remember that a 1 in 53 chance of an impact in 2032 is the same as a 52 in 53 chance of a miss.

Andy Rivkin, an astronomer, planetary defense researcher and DART team member at the Johns Hopkins University Applied Physics Laboratory in Maryland, spoke to me recently, and summed up the situation perfectly. “Bottom line, you should tell the people you care about that you love them,” he said, “but not because of 2024 YR4."

View updating impact probabilities here at Sentry: Earth Impact Monitoring

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Robin George Andrews is a photographer, public speaker, and experimental volcanologist-turned-science journalist. He regularly writes about space and geosciences for outlets including the New York Times, Atlantic, National Geographic, Scientific American, and Atlas Obscura. He is also the author of Super Volcanoes: What They Reveal about Earth and the Worlds Beyond (Norton, 2021). He lives in London, England.

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In How to Kill an Asteroid, award-winning science journalist Robin George Andrews—who was at DART mission control when it happened—reveals the development of the technology that made it possible, from spotting elusive asteroids and comets to figuring out their geologic defenses and orchestrating a deflection campaign. In a propulsive narrative that reads like a sci-fi thriller, Andrews tells the story of the planetary defense movement, and introduces the international team of scientists and engineers now working to protect Earth.