Could an asteroid really hit Earth? Odds of asteroid 2024 YR4 reach ...

While YR4 still has a nearly 97% chance to completely miss Earth in 2032, its odds of impact, which now stand at 3.1%, represent the highest risk level of any large space rock ever.

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NASA observing ‘city-killer’ asteroid en route for Earth

NASA’s James Webb Space Telescope is helping astronomers study asteroid 2024 YR4, which has a small chance of striking Earth on December 22, 2032.

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The risk that an increasingly ominous asteroid dubbed 2024 YR4 will crash into Earth in seven years now exceeds the threat once posed by the infamous Apophis.

While YR4 still has a nearly 97% chance to completely miss Earth in 2032, its odds of impact, which now stand at 3.1%, represent the highest risk level of any large space rock ever. Those odds may seem low, but the newly-calculated probability of a collision with Earth is a new record – one that merits close attention from astronomers in the years ahead as they track the asteroid hurtling through the cosmos.

The asteroid YR4's chances of impact now surpass the odds that Apophis once had of colliding with Earth when it was first discovered in 2004. Fortunately, the 130-300 foot asteroid is much smaller than the cruise ship-sized Apophis and would cause far less devastation in the still-unlikely event that it crashes into Earth.

Here's what we know so far about 2024 YR4 and how NASA and other space agencies are preparing to deal with the looming threat.

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What are the odds asteroid YR4 impacts Earth in 2032?

Asteroid 2024 YR4 has been a source of alarm because it carries an uncommonly high risk of colliding into Earth.

Among the more-than 37,000 known large space rocks, it's the only one right now with any chance of hitting Earth anytime soon.

The space rock was spotted late last year and reported on Dec. 27, 2024 to the Minor Planet Center, the official authority for observing and reporting new asteroids, comets and other small bodies in the solar system. The object eventually caught the attention of NASA and other astronomers when it rose on the U.S. Space Agency's Sentry Impact Risk Table, which tracks any known asteroids with a non-zero probability of hitting Earth.

Initial projections gave the asteroid little more than a 1% chance of impacting Earth on Dec. 22, 2032. Those odds have steadily increased since then, and now stand at a record 3.1%.

Asteroid 2024 YR4 also rates 3 of 10 on the Torino Impact Hazard Scale, a method for astronomers to categorize and rate the threat of near-Earth objects. The scale ranges from 0 (no chance of impact) to 10 (a collision is certain and would cause worldwide devastation.)

Astronomers expected for YR4's odds of impact to rise before they go down as scientists continue to make more accurate observations of its trajectory. Still, any rating on the Torino scale above a 0 is unusual, which is why the world's space agencies have taken notice.

What would happen if YR4 crashed into Earth?

Even though the asteroid is relatively small, an impact with Earth could still cause significant devastation – especially if it were to have a direct hit on a city.

If it did collide with Earth, an asteroid of that size could cause an explosion in the atmosphere or even create an impact crater, according to the Planetary Society. Both possibilities would likely cause devastating damage on the ground, though not enough for it to be a mass extinction event.

The International Asteroid Warning Network put out a list of possible impact locations, which largely includes empty ocean and uninhabited or sparsely populated areas in the eastern Pacific Ocean, northern South America, the Atlantic Ocean, parts of Africa, the Arabian Sea and South Asia. But some possible impact locations are densely populated areas.

How was Apophis ruled out as a threat?

When Apophis was first spotted two decades ago, it initially carried a 2.7% chance of impacting Earth during its 2029 flyby – then a record.

While YR4's impact odds have unseated Apophis, the larger asteroid still briefly hit a higher rating of 4 on the Torino Scale.

A radar observation campaign in March 2021 during a distant flyby that – combined with precise orbit analysis – is what eventually allowed astronomers to determine that the asteroid poses no risk of crashing into Earth for at least a century.

Instead, Apophis, which measures a quarter of a mile long, is projected to come within 20,000 miles of our planet’s surface on April 13, 2029. The approach, which is closer than telecommunications satellites, will mark the closest any large asteroid has ever come to Earth, according to the ESA.

How might NASA, other agencies mount a planetary defense?

The asteroid will continue to be visible from Earth through April, giving astronomers some time to gather data with ground-based telescopes. While the asteroid won't again be observable from Earth until June 2028, NASA’s James Webb Space Telescope will be able to study it in March from orbit.

"As more observations of the asteroid’s orbit are obtained, its impact probability will become better known," NASA said in a recent blog post. "It is possible that asteroid 2024 YR4 will be ruled out as an impact hazard, as has happened with many other objects."

NASA and the European Space Agency also plan to send uncrewed spacecraft to observe Apophis in the years ahead to map and study its surface to gain further insights into near-Earth asteroids.

It's one of the many plans the agencies have in place as part of a larger effort to build a defense to protect humanity from threats posed by asteroids and other inbound space rocks.

In September 2022, NASA demonstrated that it was possible to nudge an incoming asteroid out of harm's way by slamming a spacecraft into one as part of its Double Asteroid Redirection Test, or DART. And as of October, a craft from the European Space Agency is on the way to get an up-close look at the asteroid's remnants.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at elagatta@gannett.com