Space Junk Set to Crash Into Moon Shows Debris Problem Is Spreading Beyond Earth

Lunar impacts are nothing new. Space agencies have slammed spacecraft into the moon for more than 60 years to dispose of them or study the craters they create. And the moon is pocked with naturally occurring impact craters estimated to number in excess of 100,000. But Friday’s event marks the first unintentional impact of human-made debris on the lunar surface, according to the European Space Agency.

Space debris is common closer to our planet—the agency said there are 36,500 pieces of junk larger than 4 inches in Earth orbit. But Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who keeps a catalog of space debris, called the looming impact “a harbinger.”

“Deep space is about to go through the transition low-Earth orbit went through 30 years ago,” he said.

The impending shift has some astronomers calling for a new era of space environmentalism, in which the final frontier is given similar protections to those we accord to terrestrial ecosystems.

Once rocket boosters or upper stages get used up during a launch, they can wind up in orbit around the sun or fall back toward Earth, burning up as they re-enter the atmosphere. But sometimes—which seems to be the case here—spent rocket parts meander into higher, elongated orbits around the Earth and cross paths with the moon.

“People have put junk into higher orbits of this sort, and just kind of forgotten about it,” said Bill Gray, an astronomer with Project Pluto, a Maine-based firm that supplies software used to track the trajectories of near-Earth objects.

Mr. Gray was the first to announce the impending lunar impact. He did so in late January, after observations revealed that an object he had first spotted traveling between Earth and the moon in 2015 had returned to the neighborhood.

He thought initially that the rocket body was that of a SpaceX Falcon 9 booster that launched an Earth observation satellite seven years ago. But data from the National Aeronautics and Space Administration’s Jet Propulsion Lab revealed the spacecraft’s initial trajectory—which Mr. Gray observed in 2015—didn’t take it close enough to the moon to match that of the SpaceX launch.

In mid-February, Mr. Gray said the debris in question was, instead, a spent booster from a Chinese rocket that launched the nation’s Chang’e-5 T1 spacecraft in 2014.

Astronomers from the University of Arizona and NASA have since corroborated Mr. Gray’s re-identification of the object. NASA’s Lunar Reconnaissance Orbiter would study the impact site, an agency spokesman said.

During a February press conference, China foreign ministry spokesman Wang Wenbin said “the upper stage of the rocket related to the Chang’e-5 mission entered into Earth’s atmosphere and completely burned up.”

But the Chang’e-5 mission—a successor to Chang’e-5 T1—launched in 2020, not 2014.

“I think the Ministry of Foreign Affairs simply got two different, but similarly named, lunar missions mixed up,” Mr. Gray said in a blog post.

The Chinese space agency didn’t respond to a request for comment.

Mr. Gray said the misidentification could have been avoided if companies and agencies were more transparent about the location and movements of their spacecraft.

“If, for example, SpaceX had said, this is where our booster was last seen, then I could have said this object wasn’t the SpaceX booster,” Mr. Gray added. SpaceX didn’t respond to a request for comment.

The U.S. Space Force tracks space objects in orbits up to about 22,250 miles above Earth because such debris could pose a threat to global positioning and telecommunication satellites as well as the International Space Station. NASA uses the tracking data to protect all agency assets from artificial space debris, the agency spokesman said.

But the moon is another 226,000 or so miles away—and no official entity is tracking the junk in between.

“It doesn’t fall under any jurisdiction,” Dr. McDowell said. And with growing numbers of missions aimed at establishing a long-term human presence on the moon, he added, “you probably don’t want to leave things in this space unless you’re confident that you’ve got enough tracking assets to not lose it.”

If settlements are established on the moon, he said, lunar impacts from debris could damage or destroy experimental apparatus or other infrastructure and cause harm to residents.

The region of space around the moon is much less crowded, according to Mr. Gray, who said he is now tracking a couple dozen objects. That number may quickly balloon, Dr. McDowell said, as more commercial players and smaller countries join the U.S., China and Russia in mounting deep-space missions.

“With the normalization of deep space has to come governance,” he said.

The rocket body that strikes the moon Friday will vaporize on impact, according to Mr. Gray. But the impact should mark an inflection point in the discourse over humanity’s stewardship of space, said Moriba Jah, an associate professor of aerospace engineering at the University of Texas, Austin and chief scientist of Privateer, a Maui-based startup focused on tracking objects in orbit.

Dr. Jah proposes developing what he calls a space traffic footprint. “Think of it as the burden that any given object poses on the safety and sustainability of anything else dead or alive,” he said.

“Any single one of these impacts isn’t necessarily obliterating the lunar environment, but these things add up,” Dr. Jah said, likening our approach to space junk on the moon, Mars and in Earth orbit to our species’ pollution of the ocean.

“We were like ‘the ocean’s big, everything we dump will get diluted,’” he said. “Now we’re doing the same thing with space.”

Write to Aylin Woodward at [email protected]