The upper stage of a SpaceX rocket is expected to crash into the moon early Wednesday morning, creating a fresh crater and giving scientists a rare opportunity to observe the impact and its effects.
The Falcon 9 upper stage that launched Firefly Aerospace’s Blue Ghost Mission 1 and ispace’s Resilience lunar lander on Jan. 15, 2025. After deploying both spacecraft toward the moon, the stage remained in a highly elliptical Earth orbit. Gravitational interactions with the Earth and moon gradually altered that orbit, placing it on a collision course with the lunar surface.
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Astronomers have calculated that the rocket body will strike early Wednesday morning just after 2:35 a.m. at around 5,400 mph. A crater 50-100 feet across is espected to be created as it ejects a plume of lunar dust into space. NASA’s Lunar Reconnaissance Orbiter has already imaged the predicted impact site and is expected to image it again after the impact to measure the resulting crater and compare it with computer models.
Scientists are especially interested because impacts like this are rarely predictable. The moon is constantly bombarded by meteoroids, but researchers usually find out after the event. In this case, we know the rocket stage’s mass, shape and velocity, making the collision a valuable experiment for testing models of crater formation and debris movement.
A paper published last week by a group of astronomers called on professional and amateur astronomers alike to assist in observing the impact and share the images and data collect.
The observations could also improve understanding of the lunar environment as NASA and other space agencies prepare for more frequent robotic and human missions.
Why wasn't this rocket returned for reuse?
Most orbital rockets have at least two stages, each serving a different purpose. The first stage, or booster, provides the thrust needed to lift the rocket through Earth’s atmosphere before separating a few minutes after launch. The upper stage then ignites, accelerating satellites into orbit or onward toward destinations such as the moon or Mars.
SpaceX has led the way developing a booster stage to fly again on a future mission. Returning the upper stages would require additional fuel, a heat shield and landing hardware, all of which add significant weight reducing the rocket’s payload capacity.
Instead upper stages are expendable, and cost about a quarter as much as the reusable first stage. Most de-orbit after a few weeks, burning up in the atmosphere and a few go into stable orbit as far away from more useful artificial satellites as possible.
Past impacts
Dozens of spacecraft, rocket stages and mission hardware have intentionally or unintentionally impacted the lunar surface. NASA deliberately crashed the spent Saturn V third stages from several Apollo missions into the moon between 1969 and 1972, to create artificial “moonquakes” that were recorded by seismometers left behind by Apollo astronauts. Those controlled impacts helped scientists probe the moon’s interior, revealing that seismic waves traveled through the lunar crust much differently than they do on Earth.
More recently, NASA intentionally crashed the retired LCROSS spacecraft and its attached upper rocket stage into a permanently shadowed crater near the moon’s south pole in 2009. The collision excavated material from beneath the surface and confirmed the presence of water ice in the crater, a discovery that reshaped scientists’ understanding of lunar resources and future exploration.
Other spacecraft, including Japan’s Kaguya orbiter and Europe’s SMART-1 mission, were also intentionally de-orbited onto the moon at the end of their missions.
How to watch
I short, you can't. The impact is unlikely to be visible without a sizable telescope. Because it will occur on the sunlit side of the moon, any flash will be difficult to detect against the bright surface. The best chance of seeing the event is the cloud of dust thrown into space after the collision, although even that will likely require very large amateur or professional telescopes and very favorable viewing conditions.
Whether or not the impact is seen live, spacecraft orbiting the moon should eventually reveal its effects, providing scientists with one of the best-documented lunar impacts ever observed. Both NASA’s Lunar Reconnaissance Orbiter and South Korea’s Danuri lunar orbiter are planning to image the resulting crater and lunar ejecta.