A piece of a SpaceX rocket will crash into the moon after spending nearly seven years hurtling through space, experts predict.
The Falcon 9 booster was launched by Elon Musk's space exploration company in 2015, but after completing its mission, it didn’t have enough fuel to return to Earth. The rocket’s second stage has been in an uncontrolled orbit ever since.
The rocket has been pulled by the competing gravitational forces of the Earth, moon, and sun, which has made its path chaotic, says Jonathan McDowell, an astronomer at Harvard-Smithsonian Center for Astrophysics.
"It's been dead—just following the laws of gravity,” McDowell says to Georgina Rannard for BBC. "Over the decades there have been maybe 50 large objects that we've totally lost track of. This may have happened a bunch of times before, we just didn't notice.”
While the SpaceX rocket isn’t the only piece of “space junk” orbiting Earth, it could be the first documented rocket collision with the moon, according to data analyst Bill Gray who developed software that tracks near-Earth objects. Gray predicts the rocket will hit the far side of the moon on March 4, 2022.
“I realized that my software complained because it couldn’t project the orbit past March 4,” Gray told Timothy Bella of the Washington Post. “And it couldn’t do it because the rocket had hit the moon.”
The SpaceX booster was part of the company’s first deep-space mission designed to monitor solar storms and Earth's climate, per Live Science's Ben Turner. After the booster sent the National Oceanic and Atmospheric Administration's Deep Space Climate Observatory satellite to a gravitationally-stable Lagrange point, the rocket’s second stage became derelict.
When the rocket’s second stage finally collides with the moon at roughly 5,771 mph, it will explode on impact.
"It's basically a four-tonne empty metal tank, with a rocket engine on the back. And so if you imagine throwing that at a rock at 5,000 miles an hour, it's not going to be happy," McDowell tells the BBC.
Unlike deliberate collisions with the lunar surface, this impact is not likely to reveal anything new about the moon. In 2009, NASA fired its Lunar Crater Observation and Sensing Satellite onto the moon's south pole, which released a plume of material that allowed scientists to confirm the presence of water ice.
Though the booster's crash will be largely uneventful, space debris can have serious consequences. Because of the high speed that objects travel in space (around five miles per second), a collision with even a tiny chip of free-floating paint can damage a spacecraft. Last November, astronauts in the International Space Station were forced to shelter in their spacecraft when they passed through a debris cloud from a Russian anti-satellite test. All of that space junk whizzing around the planet could complicate future space travel.
"If we get into the future where there are cities and bases on the moon, we want to know what's out there,” McDowell tells the BBC. “It's much easier to get that organized when there is slow traffic in space, rather than waiting until it's a problem."