NASA tracks a 'city-killer' asteroid that might hit Earth

A newly detected asteroid, nearly the size of a football field, has caught the attention of astronomers due to its increased likelihood of colliding with Earth in eight years.

While the probability remains low—currently at 1.6%—such an impact could unleash devastation comparable to hundreds of Hiroshima bombs, depending on where it strikes.

A cosmic threat on the radar

Dubbed 2024 YR4, the asteroid was first spotted on December 27, 2024, by Chile’s El Sauce Observatory. Early observations suggest it measures between 130 and 300 feet (40–90 meters) in width.

By New Year’s Eve, NASA’s acting planetary defense officer, Kelly Fast, flagged it as a potential threat. “You get observations, they drop off again. This one looked like it had the potential to stick around,” Fast told AFP.

By January 29, the International Asteroid Warning Network (IAWN) issued a memo confirming its increased risk.

NASA’s Jet Propulsion Laboratory calculations indicate that if it were to impact Earth, potential sites include the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia.

Understanding the threat

2024 YR4 follows an elongated four-year orbit, looping through the inner solar system before heading past Mars and Jupiter. For now, it is moving away from Earth and won’t return for another close approach until 2028.

Planetary defense experts, while concerned, emphasize that further observations over the next months or years will likely refine calculations and potentially rule out an impact entirely. A similar scenario played out in 2004 when asteroid Apophis was initially thought to have a 2.7% chance of hitting Earth in 2029, only to be later deemed harmless.

What would an impact look like?

If 2024 YR4 were to hit Earth, it would likely explode mid-air rather than striking the ground, similar to the Tunguska Event of 1908 when a 30- to 50-meter space rock flattened 80 million trees across 770 square miles of Siberia.

Scientists estimate that the 2024 YR4 explosion could release around eight megatons of TNT—more than 500 times the power of the Hiroshima bomb.

The level of devastation would depend on the location of the impact. A blast over the ocean could trigger a tsunami, while a strike near a major city could cause catastrophic destruction.

“If you put it over Paris or London or New York, you basically wipe out the whole city and some of the environs,” said Bruce Betts, chief scientist of The Planetary Society.

Can we stop it?

Fortunately, the long warning time allows for potential intervention. NASA’s 2022 DART mission successfully demonstrated a method known as a kinetic impactor, where a spacecraft deliberately crashes into an asteroid to alter its trajectory.

“I don’t see why it wouldn’t work again,” said Andrew Rivkin, a planetary astronomer at Johns Hopkins Applied Physics Laboratory.

However, the challenge would be securing global cooperation and funding for such a mission, especially if the projected impact zone falls outside major world powers.

Other potential strategies include using high-powered lasers to vaporize part of the asteroid and create a propulsion effect or deploying a “gravity tractor”—a large spacecraft that would gradually shift the asteroid’s path using gravitational pull.

While the discovery of the 2024 YR4 is a stark reminder of Earth’s vulnerability to space objects, experts stress that there is no immediate reason for fear.

Continued tracking and research will help refine the asteroid’s trajectory and, if necessary, determine the best course of action.

“Nobody should be scared about this,” said Fast. “We can find these things, make these predictions, and have the ability to plan.”

For now, scientists worldwide are closely monitoring the asteroid, ensuring that humanity will be ready.