Inside the hunt for the most dangerous asteroid ever

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**Robin George Andrews** (0:33)
Robin George Andrews writes, Inside the hunt for the most dangerous asteroid ever.
If you were told that the odds of something were 3.1 percent, it really wouldn't seem like much. But for the people charged with protecting our planet, it was huge. On February 18, astronomers determined that a 130 to 300 foot long asteroid had a 3.1 percent chance of crashing into Earth in 2032 Never had an asteroid of such dangerous dimensions stood such a high chance of striking the planet. For those following this developing story in the news, the revelation was unnerving. For many scientists and engineers, though, it turned out to be, despite its seriousness, a little bit exciting. While possible impact locations included patches of empty ocean, the space rock, called 2024 YR4, also had several densely populated cities in its possible crosshairs, including Mumbai, Lagos and Bogota. If the asteroid did in fact hit such a metropolis, the best case scenario was severe damage. The worst case was outright total ruin. And for the first time, a group of United Nations-backed researchers began to have high-level discussions about the fate of the world. If this asteroid was going to hit the planet, what sort of space flight mission might be able to stop it? Would they ram a spacecraft into it to deflect it? Would they use nuclear weapons to try to swat it away or obliterate it completely?
At the same time, planetary defenders all over the world crewed their battle stations to see if we could avoid that fate. And despite the sometimes taxing new demands on their psyches and schedules, they remained some of the coolest customers in the galaxy. I've had to cancel an appointment saying I cannot come, I have to save the planet, says Olivier Anel, an astronomer at the European Southern Observatory and one of those who tracked down 2024 YR4. Then, just as quickly as history was made, experts declared that the danger had passed. On February 24, asteroid trackers issued the all-clear, Earth would be spared, just as many planetary defense researchers had felt assured it would. How did they do it? What was it like to track the rising and rising and rising danger of this asteroid, and to ultimately determine that it had missed us? This is the inside story of how, over a span of just two months, a sprawling network of global astronomers found, followed, mapped, planned for, and finally dismissed 2024 YR4, the most dangerous asteroid ever found, all under the tightest of timelines, and, for just a moment, with the highest of stakes. It was not an exercise, says Hainault. This was the real thing. We really had to get it right.
In the beginning, December 27, 2024, the Asteroid Terrestrial Impact Last Alert System, Hawaii.
Long ago an asteroid in the space rock highway between Mars and Jupiter felt a disturbance in the force, the gravitational pull of Jupiter itself, king of the planets. After some wobbling back and forth, this asteroid was thrown out of the belt, skipped around the sun, and found itself on an orbit that overlapped with Earth's own.
I was the first one to see the detections of it, Larry Deneau of the University of Hawaii recalls, a tiny white pixel on a black background. Deneau is one of the principal investigators at the NASA-funded Asteroid Terrestrial Impact Last Alert System, Atlas Telescopic Network. It may have been just two days after Christmas, but he followed procedure, as if it were any other day of the year, and sent the observations of the tiny pixel onward to another NASA-funded facility, the Minor Planet Center, MPC, in Cambridge, Massachusetts. There's an alternate reality in which none of this happened. Fortunately, in our timeline, various space agencies, chiefly NASA, but also the European Space Agency and the Japan Aerospace Exploration Agency, invest millions of dollars every year in asteroid-spotting efforts. And while multiple nations host observatories capable of performing this work, the US clearly leads the way. Its Planetary Defense Program provides funding to a suite of telescopic facilities solely dedicated to identifying potentially hazardous space rocks. At least, it leads the way for the moment. The White House's proposal for draconian budget cuts to NASA and the National Science Foundation mean that several observatories and space missions linked to Planetary Defense are facing funding losses or outright terminations.