An old rocket will slam into the far side of the moon on 4 March and no one is accepting ownership of the space junk – similar objects could pose a safety risk for future crewed lunar missions

Whose moon rocket is it? China has denied it is the owner of a rocket that is about to hit the moon – but experts believe it is. The confusion has highlighted our inadequacies in tracking space junk, particularly at remote distances from Earth, with implications for returning humans to the moon.

In January, astronomers announced that a human-made object was set to hit the far side of the moon on 4 March. Initially identified as the upper stage of a SpaceX Falcon 9 rocket that took off in 2015, later analysis showed it was more likely to be part of a Chinese rocket launched to the moon in 2014, a practice run for returning lunar samples to Earth in 2020.

China disagrees. In a press conference on 21 February, Wang Wenbin, a spokesperson for China’s foreign ministry, said the country’s data showed the rocket had previously “entered into Earth’s atmosphere and completely burned up”, letting China off the hook.

But Bill Gray, an independent astronomer in the US, believes China has mistaken debris from a later mission in 2020 for debris from the practice mission in 2014. “We have increasingly solid evidence,” says Gray, including analysis of paint on the object headed towards the moon that links it to China. “I don’t think anybody at this point is seriously considering it being anything else.”

The issue has highlighted that tracking space debris, especially at large distances from Earth, is extremely difficult. Experts use launch data to estimate where objects like these will go, but making accurate predictions without an easy way to follow them in space – particularly if they fly past the moon – is difficult. “It’s an intrinsically hard problem,” says Jonathan McDowell at the Harvard-Smithsonian Center for Astrophysics. “Sometimes, we make mistakes.”

While debris is tracked in low Earth orbit by organisations like the US military, no official body is tracking debris further out to the moon’s orbit. Instead, people like Gray and McDowell do the job in their spare time. “We are the only people keeping track of these things,” says Gray.

That doesn’t pose many problems for now; only a few dozen human-made objects are in distant orbits around the moon. But lunar activity is set to increase in the coming years, with multiple uncrewed missions set to launch before NASA hopes to return humans there later this decade.

“We’ve got nine missions going to the moon this year alone,” says Alice Gorman at Flinders University in Adelaide, Australia. “Fast forward 10 years and somebody might have an industrial installation at the moon’s south pole. If there’s an uncontrolled re-entry of some random thing, those risks are very different.”

Holger Krag, space safety manager for the European Space Agency, says one solution might be to designate regions of the moon where objects can be disposed, similar to how a portion of the South Pacific Ocean is used to crash dead spacecraft and even entire space stations. “We need to decide on these things pretty soon,” says Krag. Spent rocket boosters could also be equipped with tracking beacons “so you always know where they are”, says Gorman.

For now, our knowledge of these objects relies on the spare time of people like Gray. “I don’t think this really should be something that is left to one person,” he says. “I may wind up getting a different job.”