NASA Raises Odds Of City-Killer Asteroid Smashing Into The Moon

What was once dubbed a potential "city-killer" asteroid for Earth now has its sights redefined. New observations from NASA's James Webb Space Telescope (JWST) increase the odds of a collision with the Moon instead in 2032. While the risk to Earth remains negligible, the prospect of a lunar impact by asteroid 2024 YR4 is now a compelling 4.3%, perhaps offering scientists a minute but rare opportunity to study a cosmic impact event.

Asteroid 2024 YR4, first detected on December 27 last year by the ATLAS telescope system in Chile, quickly garnered international attention. Initial calculations placed it at the top of the Torino Impact Hazard Scale, with Earth impact probabilities peaking at 3.1% in February. The roughly 174- to 220-foot wide (53-67 meters) space rock, comparable in size to a 10-story building, earned its ominous "city-killer" moniker due to its potential to cause significant localized damage if it were to strike a populated area.

However, as more ground-based observations rolled in through early 2025, the risk to Earth has steadily diminished, with NASA issuing an "all clear" later in February as the Earth impact probability fell to a fraction of a percent. But as one door closed, another opened: the Moon.

In May, an international team led by Dr. Andy Rivkin of the Johns Hopkins Applied Physics Laboratory utilized JWST's Near-Infrared Camera to precisely track 2024 YR4. These observations, combined with analysis from NASA's Center for Near-Earth Object Studies (CNEOS), have dramatically improved the certainty of the asteroid's trajectory. According to NASA, the Webb data refined the asteroid's projected location on December 22, 2032, by nearly 20%.

This revised number has thus nudged the probability of a lunar collision from 3.8% to 4.3%. While still a relatively small chance, it's significant enough to excite the scientific community. Richard Moissi, head of the European Space Agency's planetary defense office, remarked, "the possibility of getting a chance for an observation of a sizable Moon impact is indeed an interesting scenario from a scientific point of view."

Should 2024 YR4 strike the Moon, NASA assures that it will not alter the Moon's orbit, although it would provide invaluable research data  Scientists anticipate that any debris ejected from a lunar impact would likely burn up harmlessly in Earth's atmosphere. 

For now, asteroid 2024 YR4 has dipped behind the Sun and out of view for Earth- and space-based telescopes. Scientists eagerly await its return in 2028, when its orbit will bring it closer to Earth, providing another opportunity to refine its trajectory and further confirm its lunar rendezvous odds.