Moon at risk? Asteroid the size of Leaning Tower of Pisa might not hit Earth, but odds of it striking the Moon have just increased

In December 2024, astronomers discovered asteroid 2024 YR4, a space rock that routinely crosses Earth's orbit. Observations by the James Webb Space Telescope (JWST) in May 2024 have refined the asteroid's trajectory, revealing a slightly increased chance of a lunar impact on December 22, 2032, now at 4.3%. While there is no risk of the asteroid impacting Earth in the foreseeable future, scientists are closely monitoring its path and welcome a potential lunar impact as a valuable learning opportunity.

Asteroid 2024 YR4 is estimated to be between 174 and 220 feet in diameter. This is about the size of the Leaning Tower of Pisa.

Early projections indicated a potential Earth collision in 2032, with impact odds peaking at 3.1% in February. Subsequent observations with JWST and ground-based telescopes reduced the Earth impact probability to zero.


The probability of a lunar impact, however, has increased. The initial JWST imaging in March reported a 3.8% chance of a lunar collision.

"As data comes in, it is normal for the impact probability to evolve," NASA representatives wrote in the statement.

The asteroid was observed by JWST's Near-Infrared Camera in May. These observations allowed scientists to calculate the space rock's trajectory with greater precision.

The range of possible locations for 2024 YR4 on Dec. 22, 2032, has decreased as NASA gained more data. This improved the certainty of the asteroid's position.

If an asteroid of this size were to impact Earth, it could cause significant damage. It could wipe out a city with the equivalent force of 500 Hiroshima bombs.

A collision with the moon would create a new crater. However, it would not be devastating to Earth's satellite.

Some scientists view a lunar impact as a positive event. It would provide a valuable opportunity to study asteroid impact prediction.

"We've got our fingers crossed for a moon impact," Alan Fitzsimmons , a physics and math professor at Queen's University Belfast in the U.K. who was not involved in the JWST observations, told New Scientist in March.

"It would have no effect on Earth, but would allow us to study the formation of a lunar crater by a known asteroid for the very first time."

The asteroid is currently moving toward the outer solar system. It is beyond the view of Earth-based telescopes.