Bill Gray was tracking a SpaceX rocket orbiting near the moon from his home in Maine when his computer software gave him a reading he didn’t expect. Gray said he had kept track of the “chaotic orbit” of the Falcon 9 booster, which launched in 2015 as part of a mission to send a space weather satellite on a million-mile journey. The rocket’s derelict second stage has since hurtled through space for years.
This month Gray, an independent researcher in orbital dynamics, figured out why he couldn’t get readings on the booster to show up on his Project Pluto software after early March: The SpaceX rocket is on a collision course with the moon, he said.
“I realized that my software complained because it couldn’t project the orbit past March 4,” Gray, who has tracked space junk, asteroids and objects near Earth for about 25 years, told The Washington Post. “And it couldn’t do it because the rocket had hit the moon.”
Since his blog post this month, other space observers have confirmed the data and agreed that the rocket, which weighs about 4 metric tons, is set to crash into the far side of the moon in March, in what Gray believes might be “the first unintentional case” of space junk hitting the moon. The expected crash will create a new crater, but it will not significantly damage the moon, Gray said, noting that it’s “built to take this sort of abuse.” The rocket is projected to touch down at a velocity of about 2.58 km a second, or about 5,770 mph.
While some astronomers have noted that the news of the rocket hitting the moon is interesting but “not a big deal,” Gray’s finding has shined new light on the potential rising issues surrounding space junk floating in deep space.
“As more players get into deep space, we need to have more attention paid to the junk that we’re leaving out there,” said Jonathan McDowell, an astronomer at the Harvard Smithsonian Center for Astrophysics who confirmed Gray’s findings. “It’s not as much about what SpaceX does now because it’s a perfectly standard practice to leave your junk in deep Earth orbit and just abandon it.”
A spokesman with SpaceX did not immediately respond to a request for comment Wednesday.
SpaceX launched its first interplanetary mission in February 2015 from Cape Canaveral, Fla. The Falcon 9 traveled 1 million miles — a distance nearly four times farther than the moon — to help the National Oceanic and Atmospheric Administration’s Deep Space Climate Observatory start its journey to Lagrange Point 2, a gravitationally stable solar orbit on the opposite side of the sun from our planet.
But after the rocket’s second stage completed a long burn to reach a transfer orbit, it was so high that the booster did not have enough fuel to return to Earth’s atmosphere. Meteorologist Eric Berger explained in Ars Technica that the rocket also “lacked the energy to escape the gravity of the Earth-Moon system,” which resulted in the booster’s chaotic orbit for nearly seven years.
“For launches of spacecraft intended to orbit the Earth, the best practice is to reserve enough fuel in a rocket’s upper stage to return it to Earth’s atmosphere, where it will burn up. This is what SpaceX and most Western rocket companies customarily do to help control debris in low Earth orbit,” Berger wrote. “The moon, of course, has no atmosphere for the stage to burn up in.”
Gray, 57, said there are at any given time dozens of objects in high orbits around the moon that move slowly enough for him and colleagues to take a short series of observations. He’s been tracking the SpaceX rocket every few weeks or months and updating its orbit using his software.
The expert, whose Project Pluto astronomical software provides commercial and freeware data research to amateur and professional astronomers, knew there were three possibilities for an object traveling in such a chaotic orbit: The rocket could hit the moon, hit Earth or pick up enough energy so that it goes past the moon and is thrown around the sun.
“I’ve always been hopeful for one to hit the moon because we really don’t learn anything from the other cases,” he said.
Once he saw Jan. 14 that the rocket was expected to crash into the moon, Gray reached out to a group of astronomers to confirm that the data was correct. He noted the group consisted of several amateur-level astronomers in the United States and Europe who “do professional-level work” — and that their observations matched with his.
“When a couple of them sent in their results, they confirmed the initial data and made the actual impact time and location considerably more certain,” Gray said.
Space junk and debris has long been an issue. The Associated Press reported last fall that NASA tracks about 20,000 pieces of space junk, including old and broken satellites. NASA abruptly called off a spacewalk shortly before it was set to begin in November after receiving a notification that space junk could threaten the astronauts outside the International Space Station. The notice came weeks after Russia fired a missile that destroyed a dead satellite, polluting low Earth orbit with more than 1,500 pieces of debris that forced the astronauts and cosmonauts to evacuate the space station and board their spacecraft in case they had to flee.
A NASA spokesman did not immediately return a request for comment.
Private space companies have had other notable instances of space junk hitting the moon. In April 2019, Beresheet, the lunar lander for Israel Aerospace Industries, became the first private spacecraft to land on the moon. But when Beresheet crashed, the lunar lander spilled thousands of tardigrades — microscopic animals also known as water bears that are regarded as the toughest animals on the planet — onto the moon, according to Wired.
McDowell said he hopes lawmakers will give the same amount of attention to space junk in deep orbit as they have in recent years for space junk floating near the planet.
“It’s a big space out there, and if something ends up hitting the moon or ends up reentering the Earth’s atmosphere or going into orbit around the sun, the attitude has kind of been, ‘So be it.’ That may change as we get busier on the moon,” he said. “Deep-space junk is by no means a threat or a crisis at the moment, but it is something that we’re in the early stages now.
“This SpaceX case is a marker that deep space is just starting to get busier, and it’s time to start thinking about our policies for deep space,” he said.
Gray said the rocket’s collision with the moon will probably go unobserved from Earth. He and McDowell highlighted how the booster’s crash would result in a fresh lunar crater caused by an object whose properties researchers understand and can learn from.
What astronomers learn from the crash is likely to be incremental, Gray said, but the March 4 collision could offer a fresh look below the lunar surface. Gray said he wonders if the expected crash could increase interest in learning about space junk in deep space.
“People are understandably concerned about the amount of space junk that’s out there,” he said. “But when it comes to tracking stuff going around the moon, I have not heard of anyone else paying attention to it.”