The possibility that a huge space rock — once deemed the riskiest asteroid ever observed — could hit the moon now appears to be off the table.Discovered at the end of December 2024, asteroid 2024 YR4 at first seemed a serious threat to Earth, with scientists estimating as much as a 3.1% chance of it impacting our planet on December 22, 2032. A series of observations from ground- and space-based telescopes quickly helped rule that out, but by June 2025, a new concern emerged: a 4.3% chance YR4 would slam into the moon instead.While Earth wouldn’t face any significant physical danger if the building-size asteroid struck the moon, researchers suggested that any astronauts or infrastructure on the lunar surface at the time could be at risk — as could satellites that we depend on to keep vital aspects of life, including navigation and communications, running smoothly.AdvertisementAdvertisementAstronomers didn’t expect to get a chance to better assess the risk of a YR4 lunar impact until the asteroid came back into view from Earth’s perspective in 2028. However, Dr. Andy Rivkin, planetary astronomer from the Johns Hopkins University’s Applied Physics Laboratory in Maryland, and Julien de Wit, associate professor of planetary science at the Massachusetts Institute of Technology, spied an opportunity for an earlier glimpse.Rivkin and de Wit applied and received approval to use the James Webb Space Telescope, or JWST, the only observatory with a chance of spotting the asteroid before 2028.Their observations, taken on February 18 and 26, improved the certainty of the asteroid’s future position. Rather than colliding with the moon, YR4 will pass it from a relatively close distance of 14,229 miles (22,900 kilometers) — narrowly ruling out a once-in-a-lifetime lunar impact that humanity would have witnessed.Rivkin and de Wit’s Webb observations were among the faintest ever made of an asteroid, according to NASA and the European Space Agency — and the detections weren’t easy to come …
