The Moon is constantly accosted by impacts from the Universe at large.
Later this year, our closest neighbor in space is predicted to be hit at seven times the speed of sound by an earthly projectile roughly the height of a five-story building: the upper stage of a Falcon 9 rocket.
According to an analysis by independent astronomer Bill Gray, developer of the Project Pluto software used to track near-Earth objects, the spent SpaceX rocket stage will crash into the Moon on 5 August 2026 at about 06:44 UTC (02:44 EDT).
Gray reports the impact should occur around Einstein crater, a heavily impacted area at the threshold between the lunar near side and far side.
"The motion of space junk is mostly quite predictable; it simply moves under the influence of the gravity of the Earth, Moon, Sun, and planets. We know those with immense precision," Gray explains.
At the same time, solar radiation pressure, or the push exerted by sunlight, is constantly acting on the object in ever-changing ways.
Though this force is slight, it adds up unpredictably over time because the object is tumbling through space, catching and reflecting more or less light depending on its position.
The SpaceX Falcon 9 is a partially reusable rocket, standing 70 meters (230 feet) tall and weighing 550,000 kilograms (1.2 million pounds) at liftoff. Its first, larger stage returns to Earth and alights on a barge so it can be refilled and re-flown, while the second stage remains in orbit.
This Moon-bound upper stage belonged to the 2025-010D Falcon 9 rocket, which launched in January 2025 and carried a payload that included two Moon landers, the Blue Ghost mission 1 and the Hakuto-R Mission 2.
And while the non-reusable second stages from many previous Falcon 9 launches have fallen back onto Earth or have entered orbits around the Sun, this one remains local.
That second stage of the Falcon 9 currently takes approximately 26 days to orbit our planet. At its closest approach, or perigee, it buzzes within 220,000 kilometers (137,000 miles) of Earth before swinging out to around 510,000 kilometers at apogee, its farthest point.
In doing so, its path intersects the gravitational track of the Moon, which is situated at an average distance of approximately 400,000 kilometers from Earth.
"The orbit of the Moon and of this object, roughly speaking, intersect. Usually, one goes through the intersection point while the other is someplace else," Gray says.
Then, as in a common sitcom plot to reunite estranged lovers, gravity will force them to meet: "on August 5, they'll reach that point at the same time," Gray says, culminating in an orbital dance that can be tracked by checking the box for 2025-010D.
This is far from the first time that the Moon has accommodated a ballistics experiment from its planetary partner. In the 1970s, multiple Apollo modules smashed onto the lunar surface, creating small 'moonquakes' to study the Moon's composition (alas, no cheese).
In 2009, NASA crashed its LCROSS probe into the Moon, kicking up dust that had lain in shadowy repose for billions of years and revealing the presence of water ice and other useful chemicals.
The most recent, similar lunar impact occurred in 2022, when what's thought to have been a Chang'e 5-T1 booster crashed on the lunar far side. The impact left an intriguing double-crater formation, imaged by NASA's Lunar Reconnaissance Orbiter.
The Falcon 9 collision is also expected to leave a fresh crater. The flare of impact will probably not be visible from Earth, but the Lunar Reconnaissance Orbiter may eventually image the aftermath.
Fortunately, this impact poses no danger.
There are no humans or structures to be harmed by raining rocket debris – our stalwart satellite is inhabited only by hundreds of thousands of pounds of technological junk and many bags of astronaut feces, urine, and vomit; as well as a couple of golf balls and a stack of $2 bills with unimaginable collector's potential.
But the broader problem is growing.
Reckless space-junk disposal threatens satellites and may endanger humans and equipment sooner rather than later.
Artemis IV aims to carry two astronauts to the Moon in 2028, and a Chinese mission aims to do the same circa 2030.
Both programs are part of a much larger push toward long-term lunar activity.
Related: Giant New Moon Scar Is a Once-in-a-Century Crater, Scientists Discover
Though it may only be feasible for Moon-bound objects, the simplest way to avoid such lunar impacts, Gray says, could be "to put upper stages in orbits where they will leave the Earth and Moon, and end up in orbit around the sun, such that they won't hit us for a long time."
And what happens after that time, potentially hundreds or thousands of years, will be a problem for future us.
Gray's analysis report is published on Project Pluto.