Astronomers say Asteroid 2024 YR4 will dodge the moon entirely in 2032, ending speculation about a possible collision with Earth’s nearest solar system neighbor.
But the missed strike means the door closes on a once-in-a-lifetime scientific opportunity.
New observations from the James Webb Space Telescope, a joint observatory between NASA and its European and Canadian counterparts, allowed scientists to calculate the asteroid‘s trajectory with greater precision. The latest findings rule out a lunar collision on Dec. 22, 2032. Instead, the asteroid will safely pass about 13,200 miles away from the lunar surface.
Astronomers track near-Earth objects in space because understanding their paths helps scientists assess potential hazards to Earth. A crash on the moon would not have threatened people. In fact, lunar debris would almost certainly have stayed near the moon, and the impact would not be severe enough to change the moon’s orbit. But it would have offered a rare chance to learn from a known asteroid hitting another planetary surface.
What is Asteroid 2024 YR4?
The asteroid itself is about 200 feet across — more than half the length of a football field. Scientists first spotted it in late 2024 with the Asteroid Terrestrial-impact Last Alert System station in Chile. Early predictions suggested a slight risk that the object could hit Earth in 2032. Follow-up observations later ruled out that possibility.
“It’s typical to have initial observations and risk models updated once additional observational data is gathered and models are able to be refined,” NASA said in a blog post on Thursday.
Even after the Earth risk disappeared, scientists estimated about a 4-percent chance the asteroid might strike the moon. That uncertainty remained because the asteroid moved farther away and became too faint for most telescopes to look at it.
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Most asteroids are the rubble left over from the formation of the solar system about 4.6 billion years ago. They’re usually too far away from Earth to pose a threat to people. But because no one wants to repeat the dinosaurs’ misfortune, keeping an eye on the ancient rocks and comets zooming through space is paramount.
Webb telescope’s latest observations
Tracking Asteroid 2024 YR4 again this year required some ingenuity. Many astronomers believed they wouldn’t get another chance until 2028, but an international team identified two short windows last month — Feb. 18 and 26 — when Webb might still detect the space rock. The telescope observes only a small patch of sky at a time, so astronomers had to predict the asteroid’s position with extreme accuracy to point the instrument correctly.
The team compared the asteroid’s location with background stars mapped by the Gaia spacecraft, a European mission. Those measurements allowed scientists to refine the asteroid’s orbit — the route it takes around the sun — and rule out a lunar impact.
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The good news: Astronomers know they can combine new cutting-edge instruments to track small, distant asteroids years in advance. Teams including NASA’s Center for Near-Earth Object Studies rely on those calculations to monitor space rocks and comets that could someday pose a real threat to Earth.
The bad news: The miss means scientists won’t get a rare natural experiment to collect data on a large asteroid strike. Telescopes and spacecraft could have otherwise watched the impact flash and measured the debris thrown into space. Missions such as the Lunar Reconnaissance Orbiter could have photographed the fresh crater.
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Those observations could help plan for potentially dangerous asteroids in the future.
“The moon is safe, 2024 YR4 poses no danger, but the work continues,” the European Space Agency said Thursday. “If a genuine danger ever emerges, we will not be caught unaware.”
