A four-tonne piece of a SpaceX Falcon 9 rocket is expected to crash into the moon on Wednesday, an unintentional collision that will bring an end to the discarded upper stage's long drift through space and carve out a new crater on the lunar surface. The object, roughly the size of a school bus, is on course to hit the moon at about 5,400 miles per hour.
The object is the second stage of the Falcon 9 rocket that launched a lunar lander from Firefly Aerospace toward the moon in January 2025. After the upper stage completed its task, it was left in space and has been adrift since then. Its orbit has now put it on a collision course with the moon, and there is no active system on board that could change its path.
The collision was not planned and is not part of any scientific mission. Even so, researchers are treating it as a rare research opportunity. The force of the impact is expected to dig out a new crater, and scientists have said the event can provide useful information about what happens when a large human-made object strikes the moon without any controlled descent.
NASA has said it will attempt to observe the impact. Observations made before, during and after the crash could help scientists study how craters form on airless bodies and how the lunar surface responds to the shock of a high-speed collision.
The impact is also scientifically valuable because the object's mass, size and speed are already known. That gives researchers a well-defined set of conditions to compare with the crater that forms, which is not usually possible with random asteroid impacts.
The impact poses no danger to Earth. The moon is far beyond Earth's atmosphere, and the crash is expected to affect only the lunar surface. No people or property are at risk.
Because the moon has essentially no atmosphere, the rocket stage will not burn up or slow down as it approaches the ground. It will not break into small pieces the way objects do when falling through Earth's air. Instead, it is expected to hit the surface intact, which is why the collision should leave a clearly defined crater.
The episode shows how leftover launch hardware can produce unexpected results long after a mission is over. The Falcon 9 upper stage completed its original job in January 2025, but after months adrift, its journey will end Wednesday with an impact that no one planned and no one can prevent.
