Asteroid 2024 YR4: NASA Confirms No Threat to Earth, Possible Lunar Impact

The phrase 'city-killer asteroid' has quickly gone viral online after scientists tracked a near-Earth object known as 2024 YR4, triggering widespread curiosity and concern. While the dramatic nickname might sound like something out of a disaster film, space agencies insist there is no reason to panic.

Asteroid 2024 YR4 was first detected in December 2024 and immediately caught astronomers' attention because of its size and early trajectory calculations. Initial estimates suggested a small chance that it could collide with Earth in December 2032. Those calculations placed the asteroid briefly high on the Torino Impact Hazard Scale, which scientists use to measure potential impact threats.

However, as additional observations were collected by telescopes and analysed by experts, the situation became much clearer. NASA has now confirmed that the asteroid does not pose a significant threat to Earth. Instead, scientists have shifted their focus to a different possibility involving the Moon, which has sparked fresh debate and renewed interest across social media.

NASA's Latest Calculations on Asteroid 2024 YR4

Asteroid 2024 YR4 is classified as a near-Earth asteroid, meaning its orbit brings it relatively close to Earth's path around the Sun. According to NASA, the space rock measures roughly 53 to 67 metres across, making it comparable to the height of a ten-storey building.

When the asteroid was first discovered, early orbital calculations suggested a small probability of its collision with Earth on 22 December 2032. At one point, the chance was estimated at just over three per cent, which was enough to prompt close monitoring by astronomers and planetary defence experts worldwide.

As astronomers gathered more data, including infrared observations from the James Webb Space Telescope, scientists refined the asteroid's trajectory. The updated analysis significantly reduced uncertainty about its path and ruled out any chance of it hitting Earth in 2032 or later.

However, the revised calculations introduced another possibility. Researchers found that the asteroid has a small chance of striking the Moon during its close pass in December 2032. Current estimates place the probability of a lunar impact at around 4 per cent, meaning there is still a roughly 96 per cent chance it will miss the Moon.

Even if such an impact were to occur, experts emphasise that it would not affect the Moon's orbit or pose a direct threat to Earth. Instead, it would simply become a rare astronomical event that scientists would study in detail.

Why the 'City-Killer' Label Went Viral

The asteroid's viral nickname has played a major role in fuelling public interest. Scientists sometimes informally describe asteroids around 50 to 100 metres in size as 'city-killers' because, if one were to strike Earth, it could potentially devastate a metropolitan area. However, that label refers to theoretical impact scenarios rather than the current risk posed by asteroid 2024 YR4.

In reality, NASA has already confirmed that the asteroid will not collide with Earth during its upcoming close approach. The primary focus now is the slim chance that it could impact the Moon instead.

If the asteroid were to hit the lunar surface, researchers estimate it could create a crater roughly one kilometre wide and release energy equivalent to several megatons of TNT. Such a collision might produce a bright flash visible from Earth and send a plume of debris into space.

Some scientists have suggested that fragments ejected from the Moon could eventually reach Earth's atmosphere, potentially creating a unique meteor display. Most of this debris would burn up harmlessly before reaching the surface, though there is also some concern that small particles could pose a temporary risk to satellites in orbit.