What will happen when a SpaceX rocket collides with the Moon?

Image source, AFP via Getty ImagesImage caption, The rocket component that will strike the Moon is the upper section of a SpaceX Falcon 9 ByKayla Epstein and Max MatzaPublished16 minutes agoThe Moon has endured countless blows over millions of years. Asteroids and meteors have given the satellite its signature pockmarked surface and network of craters. More recently, it has also experienced impacts from the plucky little probes and landers that Earthbound space agencies have sent hurtling its way. Now on Wednesday, scientists expect the Moon will experience yet another collision, this time from a drifting SpaceX rocket that has been travelling at around 2.43 kilometres per second, or about 5,400mph.The upper stage (section) of one of SpaceX's Falcon 9 rockets will "impact" the Moon on 5 August, according to Nasa's Centre for Near-Earth Object Studies (CNEOS).The US space agency reached the conclusion after independent astronomers, using public data, noted that a portion of the rocket from a January 2025 launch was on an accidental collision course with the Moon."There is no danger to Earth," said spokesperson Jimi Russell. "Nasa will continue to track the booster for training purposes, as well as later observe the impact site for scientific purposes."Why is space junk such a big problem?SpaceX launched this specific Falcon 9 rocket as part of a US and Japanese mission to carry a pair of lunar landers and scientific equipment to the Moon last year.Part of the Falcon 9 is reusable and designed to return back to Earth for its next mission. But parts of the rocket are shed in space and remain there, stuck in orbit unless they eventually collide with another celestial body.The piece in question is the upper stage of the rocket, and is about the size of a five-storey building, with a weight on Earth of at least 4,000kg (8,800 lbs).Astronomer Bill Gray, who first discovered the trajectory, says the object will land near the Einstein Crater, which is on the part of the Moon that receives daylight and is visible from Earth. He predicts it will create a crater more than 17m (56ft) in diameter.Image source, Getty Images/NasaImage caption, The Moon's surface bears witness to countless other impacts over a period of millions of yearsThe impending collision - predicted to happen at about 02:35 EDT (06:35 GMT) on Wednesday - is expected to captivate astronomers, both amateur and professional."It's something really huge smashing into the Moon. It's not remotely dangerous, we can just watch the show," says Dr Matt Bothwell, public astronomer at the University of Cambridge."It's going to impact and its going to send up a huge plume of dust, maybe 50km into the air or more, and that's going to spread sideways over time," Bothwell said.Given the Moon's lack of atmosphere and far weaker gravitational pull, the moment of impact will be "more impressive than any [similar] explosion on Earth", Bothwell said. Nothing will slow the object down, like the atmosphere would do here on Earth - and nothing will prevent the estimated million kilograms in debris from rocketing up into space.While the impact will not be visible from Earth with the naked eye, people with access to a sophisticated telescope may be able to see a flash radiating off the Moon's surface, Bothwell said.More significant would be the educative potential of the impact, Bothwell noted. He said this moment would present a unique opportunity to study what happens when an object hits the Moon.Scientists are therefore gearing up to watch the event closely. Big telescopes in the Americas, plus Nasa's Lunar Reconnaissance Orbiter and South Korea's Danuri probe, will track the flash, plume and new crater, and a citizen‑science project is signing up keen amateurs to film the impact too.By catching the dust plume in action, astronomers hope to turn this accidental crash into a useful experiment. Watching how much material gets thrown up, how high it goes and how it falls back should sharpen their models of lunar impacts – and even give clues about what lies just beneath the surface at the impact site, where fresh subsurface material will be exposed for the first time.Figure caption, The space junk clean-up (2018)Bothwell, the astronomer, also said the collision would provide a cautionary tale about the issue of ever-accumulating, human-made space clutter."I think more people should be more worried about space debris," Bothwell said. "Every single year we put more stuff in orbit. Sometimes the satellites just collide, and they shatter into more pieces. I think there's a worry about a runaway cascade, if we put so much stuff in orbit."According to the European Space Agency (ESA), there are around 54,000 objects floating in space that measure larger than 10cm. In total, humans have launched about 17,000 tonnes of objects into space since the Space Age began in 1957.The last dead rocket to impact the Moon was in 2022, when the Chinese Long March 3C upper stage from the 2014 Chang'e 5‑T1 mission hit the far side of the Moon - which faces away from Earth. Decades earlier, Nasa launched objects into the Moon on purpose, in order to collect data for the Apollo missions.Additional reporting by Pallab GhoshRelated topicsThe MoonSpace explorationNasaMore on this storyAbandoned rocket 'hits the Moon' - scientistsPublished4 March 2022