An abandoned four-ton piece of a SpaceX Falcon 9 rocket is expected to crash into the moon on Wednesday, an unintentional collision that will leave a new crater on the lunar surface. The event poses no danger to Earth, and scientists say it offers a rare opportunity to study what happens when a large, human-made object strikes the moon.
The object is the second stage of the Falcon 9 rocket that launched a Firefly Aerospace lunar lander toward the moon in January 2025. After completing its role in the mission, the spent upper stage remained in space instead of falling back to Earth or being guided to a controlled disposal. It has been drifting since then, and its orbit eventually put the moon in its path.
The rocket stage weighs about four tons and is roughly the size of a school bus. It is expected to hit the lunar surface at approximately 5,400 miles per hour. Since the moon has no atmosphere to slow the object down, the rocket section will not burn up before impact. Instead, it will strike the ground directly, carving out a fresh crater and scattering material around the collision site.
NASA has said it will attempt to observe the impact. The agency hopes the observations will help researchers better understand how fresh craters form on the moon and how material is ejected during a high-speed collision. Because the mass, speed, and trajectory of the incoming object are known in advance, the crash offers a documented case study for comparing the size and shape of a crater with the characteristics of the object that made it.
The impact is the result of an accident, not a planned experiment. The rocket stage was designed to carry its payload toward the moon and then be discarded, as is normal in many space missions. In this case, however, the discarded hardware did not re-enter Earth's atmosphere or splash down in a remote part of an ocean. Instead, it stayed in orbit long enough for its path to become unstable and eventually intersect with the moon.
For astronomers and planetary scientists, the event is notable because impacts of large objects on the moon are rarely observed in advance. Most lunar craters have been formed by natural meteoroids, whose exact size, speed, and angle of arrival are usually unknown. By contrast, the incoming Falcon 9 stage has been tracked since launch, giving researchers a detailed record of the object before it hits the surface.
A crater left by a spacecraft is not necessarily the same as a crater left by a natural object. The rocket stage is mostly hollow and built from lightweight metals, so the shape of the crater and the pattern of debris thrown out from the impact will reflect how an engineered structure behaves when it collides with the moon at high speed.
The collision is expected to affect only a small area of the lunar surface and will have no consequences for people on Earth. The moon has no atmosphere and no weather, so the debris will settle quickly after the impact. The main result, scientists say, will be a new crater that can be examined by instruments in lunar orbit for a long time after the event.