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Is a deadly asteroid about to hit Earth? Meet the man who can tell you

When an asteroid threatens Earth, astronomers use a rating called the Torino scale to communicate the risk. Richard Binzel, who invented the scale, tells New Scientist about his 50-year career in planetary defence

Space

Is a deadly asteroid about to hit Earth? Meet the man who can tell you

By Alex Wilkins

12 November 2025

[New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.]

Ryan Wills; Barry Hetherington; ESA; NASA; AdobeStock

Richard Binzel has been watching the skies for hazardous asteroids for more than 50 years. In 1995, he proposed the Near-Earth Object Hazard Index, later renamed the Torino scale, which rates asteroids from 0 to 10 based on how certain we are that they could hit Earth – and the potential devastation such an impact might cause.

Earlier this year, Binzel’s scale got a high-profile outing when asteroid 2024 YR4 briefly reached level 3 on the scale – the first space rock to get this high in two decades. While the risk has since faded, it won’t be the last time we need to fire up the Torino scale. But Binzel, who is at the Massachusetts Institute of Technology, says we can probably rest assured that we won’t see the very highest levels of the scale reached in our lifetimes, or even those of our grandchildren. He spoke to New Scientist about asteroid hunting, the chances of a devastating impact and the future of planetary defence.

Alex Wilkins: When you started your career, how did people view the threat of an asteroid impact?

Richard Binzel: I published my first paper in the 1970s, when I worked for [the geologist] Eugene Shoemaker, who understood that craters we see on the Earth are impact craters, so I grew up with the awareness of asteroid impacts as a natural process that still occurs in the solar system today.

If an asteroid were heading towards Earth, could you avert disaster?

In the public, it was a giggle factor. Shoemaker was just doing serious science, not paying too much attention to the public side of things, but people like [astronomers] Clark Chapman, David Morrison and Don Yeomans were beginning to see it was important to talk about this. There was a book called Cosmic Catastrophes that Chapman and Morrison wrote [in 1989], which was the first real treatment for the public. The Alvarez discovery of the K-T boundary layer [the geologic record of the Chicxulub asteroid thought to have wiped out the dinosaurs] was probably the wake-up call to greater scientific awareness that impacts can happen in modern geologic history.

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[New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.]

Why did you come up with the Near-Earth Object Hazard Index?

There was an object named 1997 XF11, which had a non-zero impact probability based on its initial orbit. Email had just become a thing. I was in a small email list with people like Brian Marsden, Yeomans, Chapman, Morrison, and we were debating what to do with this information. We wanted to release it publicly, but we wanted to make sure [of the risk]. We thought maybe we should just get a little more data, because with longer measurements of that orbit, [the probability of collision] would probably go away. Why cry wolf if this object is going to go away in a few days?

Marsden decided to write a press release, and just as he was sending it out, we found some earlier observations that gave a sufficient orbit to say [the probability of impact was] zero. I remember an email from Yeomans, who did the analysis, and the email basically said, “That’s zero, folks.” Brian went ahead with his press release, because he thought it was important to get the issue out into the public. Most of us disagreed, that that was crying wolf.

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I first presented the idea at a United Nations conference, and it was not well received
“

This set into my mind the need for some means of communicating when you discover an asteroid that has a non-zero impact probability, however small. Just be a little patient, and we’ll get enough data to make it go away. That if we discovered another object like that, we don’t want to keep it secret. That’s the worst thing we could do, because then no one ever trusts you, because they never know what you’re not telling them. So, we collectively decided that we needed to tell people what we know as soon as we can, when we know it. Then later, when it goes away, it’s not that anyone made a mistake or made an error, it’s just that we now have better information to know it goes away. That was the genesis of what was first called a Near-Earth Object Hazard Index.

An illustration of what the Chicxulub crater in the Yucatán Peninsula may have looked like shortly after an asteroid impact that may have wiped out the dinosaurs

D. Van Ravenswaay/Science Photo Library

How was it received at the time?

There happened to be a United Nations conference on near-Earth asteroids, where I first presented the idea, and it was not well-received. There were people who said we don’t need that, because we can explain the longitude and latitude and the ascending node of the orbit, and we can explain this all perfectly well. We don’t need some simple thing like a small, 0-10 scale. So, the initial response was arrogance by some astronomers that they didn’t need this, because we are smart enough and capable enough to communicate all these three-dimensional orbital characteristics that most people wouldn’t know.

But I persisted. I brought it forward again to a conference in Torino, and I had the idea that we should call it the Torino scale, because it was presented at the conference. I didn’t want to put my name on it because it would look egotistic. But if we called it the Torino scale, everyone had ownership of it and everyone would feel it useful to use, anyway.

[A graphic showing the Torino scale, which assigns asteroids a score of 0 to 10 based on their size and risk of impacting Earth]

The Torino scale assigns asteroids a score of 0 to 10 based on their size and risk of impacting Earth

Has it worked as you thought it would?

I thought it would be called into play a bit more than it has, but I think it’s because discoverers have done a good job of following up objects right away, and so if they have a non-zero probability, they go away pretty quickly.

There have been a dozen or so objects that have reached 1 on the Torino scale without much news, which is perfect. That’s exactly the intent. It’s like the Richter scale, where if you tell someone in California there’s going to be a magnitude-1 or magnitude-2 earthquake tomorrow, they go on with their day and think nothing of it.

What will future asteroid tracking look like?

The discovery rate of near-Earth asteroids is going to improve or accelerate dramatically as the Vera C. Rubin telescope and Near-Earth Object (NEO) survey telescope come online. We will discover near-Earth objects at an incredibly fast rate. Some of them will have very uncertain initial orbits that we will want to extrapolate forward for decades, so that means it’s a non-zero impact probability. It will simply take time to get enough orbital data for a long enough period that we can say more precisely where it’s going to be many decades from now, and entirely rule out an Earth impact.

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*Original source*