NASA and ESA scientists are monitoring asteroid 2024 YR4, initially feared to pose a threat to Earth, but now projected to have a small chance of impacting the Moon by 2031—potentially offering a rare opportunity to observe a lunar impact and test planetary defense strategies.
First detected by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii on December 27, 2024—two days after its closest approach to Earth—YR4 is now being closely monitored, though it is currently out of view for astronomers.
Take a deep breath, and hold off on any doomsday plans
Fortunately, the chance of YR4 actually striking the Moon stands at just 4.3 percent, with the possible impact expected in about seven years.
Still, this isn’t a minor space rock, per se—YR4 measures between 131 and 295 feet (40 to 90 meters) in diameter, roughly the size of a 10-story building, according to observations made with JWST’s NIRCam infrared camera.
NASA’s Center for Near Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory noted that the asteroid’s estimated chances of hitting the Moon increased from 1.7 percent in February to 3.8 percent in April, and now stands at 4.3 percent. If YR4 does strike, the impact is predicted to occur on the Moon’s near side—potentially allowing astronomers to witness a lunar impact crater forming in real time, an extraordinary event that some liken to a “Super Bowl” for astronomy enthusiasts.
While the scientific community continues to monitor the asteroid’s trajectory, planetary defense experts are paying particularly close attention. The size and predicted path of YR4 make it an ideal candidate for testing asteroid deflection strategies. Following NASA’s successful 2022 DART mission, which redirected the asteroid Dimorphos, the European Space Agency’s Hera mission is now preparing to study the results of that experiment.
Germany is also currently monitoring the object. OHB, the German aerospace firm behind Hera, has announced plans to launch a mission to deflect YR4—potentially in 2028, just in time for its next close approach.
YR4 belongs to the Apollo group of asteroids, a class of roughly 20,000 near-Earth objects that orbit the Sun at distances similar to Earth’s. Shortly after its discovery, researchers estimated a 1.3 percent chance of Earth impact, prompting a warning from the International Asteroid Warning Network on January 29.
Swift coordination between NASA’s JPL and the European Space Agency’s Near-Earth Object Coordination Center led to additional observations, ultimately ruling out any threat to Earth.
Although YR4 has now drifted too far for most telescopes to track, experts will be paying attention once again when it returns in December 2028 as it makes its next close approach.
Chrissy Newton is a PR professional and founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com.