An asteroid previously thought to be heading towards Earth may now collide with the moon, according to the latest calculations by NASA. About the size of a 10-story building, asteroid 2024 YR4 has just over a 4% chance of hitting the moon seven years from now.
Graphic of the possible locations – represented by yellow points – of asteroid 2024 YR4 on Dec. 22, ... More
Asteroid YR4 was first discovered by the Asteroid Terrestrial-impact Last Alert System in Hawaii on Dec. 27, 2024, two days after it came closest to Earth on its four-year orbit of the sun.
The latest observations in May by the James Webb Space Telescope’s NIRCam infrared camera suggest that YR4 is 174-220 feet (53-67 meters) in diameter, about the size of a 10-story building or the wingspan of a Boeing 747. Upon discovery, it was thought to be 131-295 feet (40-90 meters).
According to NASA’s Center for Near Earth Object Studies at the Jet Propulsion Laboratory, Webb’s latest data on its trajectory suggests there's now a 4.3% chance that Yr4 will strike the moon. That’s up from 3.8% in April and 1.7% in February.
If YR4 does strike the moon, it will do so on its near side. That would present a rare opportunity for planetary scientists to watch an impact crater being created.
Asteroid 2024 YR4 is now too far away to observe with either space or ground-based telescopes and will remain so until YR4’s next close pass in December 2028.
Its close pass — and possible impact — with the moon makes YR4 an ideal target to learn how to deflect a potentially Earth-bound asteroid. In September 2022, NASA’s Double Asteroid Redirection Test — the first demo mission to test planetary defense technology — impacted asteroid Dimorphos and successfully changed its orbit. Another probe, called Hera, is now on its way to Dimorphos to figure out what happened. The maker of Hera, OHB in Bremen, Germany, is working on a mission plan to redirect YR4 for a possible launch in 2028.
YR4 is one of about 20,000 Apollo-type asteroids that orbit the sun from about the same distance as Earth. Initial observations of YR4 in December suggested that it might strike Earth, with the International Asteroid Warning Network publishing a warning on Jan. 29 after the NASA JPL Center for NEO Studies and ESA NearEarth Objects Coordination Center calculated that 2024 YR4 had a 1.3% chance of impacting Earth. Dozens of observations by other telescopes were scheduled, which eventually enabled astronomers to rule out an impact with Earth.