A SpaceX rocket piece floating in space since last year was expected to have smashed into the moon at high speed early Wednesday morning, though the impact was unlikely to be confirmed for at least several hours.
The school-bus-size object is the second stage of a SpaceX Falcon 9 rocket that had launched a lunar lander from Firefly Aerospace toward the moon in January 2025.
Weighing 4 metric tons (4,000 kg), the rocket body had been due to hit the moon around 2:35 a.m. ET (0635 GMT), travelling at 5,400 miles per hour (8,690 kph), but none of the spacecraft orbiting the moon were expected to be in a position to capture images of the impact live.
The space junk would have kicked up a plume of lunar dust that would likely be illuminated by sunlight, but difficult to spot with the naked eye from Earth. It was likely to be at least several hours before scientists would be able to confirm the crash by studying images from telescopes in the Americas, the BBC reported.
The impact was unintentional, Reuters quoted SpaceX as saying. The rocket piece was expected to hit Einstein Crater on the moon's western limb, which is often difficult to see from Earth.
Such 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 was not until earlier this year that astronomers determined that the rocket stage, which had dumped its remaining fuel and could not 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 kicked up by the impact.
Several spacecraft intending to softly land on the moon in recent years have crashed instead.
Russia's nuclear-powered Luna-25 mission spun out of control and crashed in 2023. Its small power source of plutonium-238 likely remains harmlessly on the lunar surface.
India's Chandrayaan-2 lander mission crashed in 2019. Israel's Beresheet lander crashed that same year. Among the Israeli lander's payloads were tiny tardigrades, microscopic animals known for surviving radiation and other harsh environments and which may still be on the surface.
NASA intentionally crashed stages from its Saturn V moon rocket into the moon in the 1970s to study the impacts' seismic effects.
NASA and SpaceX are discussing ways to prevent future lunar impacts, Scheiman said. The US space agency plans to build a lunar base and send routine astronaut missions to the lunar surface beginning later this decade under its multibillion-dollar Artemis program. It would not want errant pieces of space junk impacting those assets.
