Although astronomers have ruled out a smash-up between Earth and an asteroid known as 2024 YR4 in the year 2032, the building-sized space rock still has a chance of hitting the moon. In fact, the chances — slight as they are — have doubled in the past month.
The latest assessment from NASA puts the probability of a lunar impact on Dec. 22, 2032, at 3.8%. That’s an increase from the 1.7% figure that was reported in February. Since then, further observations made by ground-based telescopes and NASA’s James Webb Space Telescope have somewhat reduced the uncertainty over where exactly the asteroid will be when its orbit intersects Earth’s orbital path (and the moon’s).
Over the course of observing 2024 YR4, astronomers had set the chances of a collision with Earth in 2032 as high as 2.3% — but that wasn’t because of what the asteroid may or may not do over the next seven years. Instead, it merely reflected how little was known about YR4’s precise orbit. The chances of an Earth impact fell to zero more than a month ago as more observations came in.
Something similar might well happen to the chances for a lunar impact. If the calculations progress the way they usually do for asteroid orbits, the chances may go up for a while but then vanish completely. Stay tuned: The Webb telescope is due to check in again with YR4 in late April or early May.
What if it turns out that the asteroid is truly on course to hit the moon? “There might be an unbelievable light show,” former NASA astronaut Ed Lu, who’s in charge of the B612 Foundation’s Asteroid Institute, said last week at the University of Washington.
