An Asteroid Could Smash Into the Moon in 2032. Here’s Why We Should Destroy It

Asteroid 2024 YR4 garnered global attention last year when astronomers estimated it could hit Earth in 2032. Though they have since ruled out that possibility, this large space rock still has a 4% chance of smashing into the Moon.

Those are pretty slim odds, but on the off chance 2024 YR4 does end up on a collision course with the Moon, the scientific community needs to be prepared. Astronomers have found evidence to suggest that a lunar impact could eject an enormous amount of micrometeoroid debris into low-Earth orbit, potentially endangering spacecraft and astronauts aboard the International Space Station.

A new study by researchers from NASA and several other U.S. institutions lays out our options for avoiding this worst-case scenario. In the paper—submitted to the Journal of the Astronautical Sciences for peer review and made available on the preprint server arXiv—the authors assess multiple strategies for deflecting or destroying the asteroid before it can slam into the lunar surface. Their conclusion? It looks like blowing it up would be our best bet.

Why we shouldn’t deflect asteroid 2024 YR4

Detonation is not typically the preferred strategy. Deflecting 2024 YR4 would ensure that no part of it could impact the Moon or Earth, whereas detonating it could turn one large, predictable threat into numerous smaller, unpredictable ones. All this said, for deflection to work, it has to be done perfectly—and that’s not a simple task given how little we know about the asteroid and the short amount of time afforded to us.

NASA demonstrated its kinetic impactor deflection technique in 2022, when the DART mission (Double Asteroid Redirection Test) rammed into the asteroid moonlet Dimorphos to change its trajectory as it orbits a larger asteroid called Didymos. Though the mission succeeded, asteroid deflection is easier said than done.

To do this accurately, astronomers need to know how much 2024 YR4 weighs to calculate the amount of energy required to alter its trajectory. This is difficult to estimate with any degree of certainty. The James Webb Space Telescope measured the asteroid’s diameter in March, finding it to be about 197 feet (60 meters) wide. But to calculate its mass, astronomers also need to know its density, and they don’t currently have a clear understanding of 2024 YR4’s composition.

According to the researchers, the asteroid’s mass could range from 74 million pounds (33 million kilograms) to over 2 billion pounds (930 million kilograms). This equates to an enormous amount of uncertainty around how much energy it would take to nudge 2024 YR4 off course. Getting this wrong could have serious consequences—potentially deflecting the asteroid toward Earth instead.

NASA could launch a reconnaissance mission to refine estimations of 2024 YR4’s mass, but the best time to do so would be 2028. That only gives the agency three years to develop the mission—an unprecedentedly tight timeframe. As such, the researchers concluded that deflection missions are impractical for preventing a lunar impact.

The case for destruction

In light of these challenges, destroying the asteroid appears to be the more viable option, according to the researchers. They outline a couple different ways NASA could go about this.

The first is a robust kinetic disruption mission. This would be similar to NASA’s DART mission, but instead of nudging the asteroid off course, the spacecraft would aim to break it apart. Unlike the DART-style impact, kinetic disruption has never been tested before. However, NASA would have a reasonable amount of time to develop this mission, as the next available launch window is between April 2030 and April 2032, according to the researchers.

Alternatively, NASA could just nuke it. Yes, really. This would involve detonating a nuclear device on, near, or beneath the surface of 2024 YR4 to break it into pieces. This hasn’t been tested before either, but it’s theoretically possible. The researchers state that the next available launch window for such a mission would be between late 2029 and late 2031.

We still have seven years before 2024 YR4 makes its close approach, and it will most likely pass safely by the Moon. Even so, this asteroid offers scientists a rare opportunity to test and refine strategies for preventing impacts on Earth and its natural satellite, ensuring we’re prepared to protect our home if the need arises.