A four-tonne piece of a SpaceX rocket has been drifting in space since last year, and on Wednesday it's finally going to do something about it: crash into the moon at high speed. The collision poses no danger to Earth, but it will leave a new crater and give scientists something to do.

The school-bus-sized object is the second stage of a SpaceX Falcon 9 rocket that launched a lunar lander from Firefly Aerospace toward the moon in January 2025. The rocket body is due to hit the moon at about 06.35am GMT, slamming into the surface at 5,400mph (8,690 km/h). It will kick up a plume of lunar dust that might be illuminated by sunlight but will be tough to spot with the naked eye from Earth.

NASA said the impact is expected to create a crater about 60ft (18 metres) wide and 12ft (four metres) deep, throwing dust and rock outward as ejecta. The rocket piece is expected to hit the Einstein crater on the moon's western limb, which is often hard to see from Earth. However, NASA will look for opportunities to image the site before and after the impact, with any data collected helping scientists 'better understand artificial impacts and their exploration implications.'

NASA's Jimi Russell said on Tuesday: 'The impact poses no danger to Earth and NASA scientists are planning to collect lunar data from the event and refine techniques for tracking objects in space.'

Such rocket parts, known as stages, typically fall back into Earth's atmosphere and burn up or plunge into the ocean after boosting the rocket's payload to a precise spot in orbit. But because the January lunar lander mission required more thrust than missions closer to Earth, the rocket's second stage remained in space, floating aimlessly among thousands of other pieces of space junk that active satellites must steer clear of.

It wasn't until earlier this year that astronomers determined the rocket stage, which had dumped its remaining fuel and cannot be controlled, was on an orbital trajectory ending at the moon. 'What has happened is essentially a mixture of solar activity and gravity forces have put it on a path toward the moon,' Julianna Scheiman, SpaceX director of NASA science and Dragon programs, told reporters on Monday.

'This may be of some - probably minor - scientific interest, and we may learn some things from it,' said Bill Gray, creator of widely used astronomy software who published a report on the stage's impact in April. 'It doesn't present any danger to anyone, though it does highlight a certain carelessness about how leftover space hardware [space junk] is disposed of.'

Space junk impacts on the moon are rare. A Chinese rocket stage crashed into the moon in March 2022 after completing a lunar test mission. In 2009, NASA intentionally crashed a rocket stage into the moon to study the plume of lunar material. Several spacecraft intending to softly land on the moon in recent years have crashed instead, including Russia's nuclear-powered Luna-25 mission in 2023 and India's Chandrayaan-2 lander mission in 2019. Israel's Beresheet lander crashed that same year; among its payloads were tiny tardigrades, microscopic animals known for surviving radiation and other harsh environments, which may still be on the surface.

NASA and SpaceX are discussing ways to prevent future lunar impacts, Scheiman said.

The collision comes as SpaceX on Tuesday reported a smaller loss than Wall Street expected along with a surge in revenue in its first quarterly report as a public company. Despite this, shares tumbled as investors remained skeptical about the company's ability to deliver on its lofty promises.