Science
An 18-Meter-Diameter Crater Formed on the Moon — What Fell Was a Falcon 9 Upper Stage
Related terms: 地学 物理基礎 天体の運動 宇宙開発
Key points (reviewing AI explanation)
The upper stage of a Falcon 9 launched in January 2025 collided with the lunar surface on August 5, 2026. NASA's Lunar Reconnaissance Orbiter photographed the impact site on August 11.
Explanation
A new crater has formed on the surface of the Moon that did not exist before. The cause was not a meteorite, but a part of a rocket launched from Earth.
The object in question is the upper stage (second stage) of a SpaceX Falcon 9 rocket launched on January 15, 2025. This launch simultaneously sent out two lunar landers: "Blue Ghost" from the American company Firefly Aerospace, and "Resilience" from the Japanese company ispace. After completing its role, the upper stage was left in space as is.
This upper stage was not originally on a trajectory that would collide with the Moon. The orbits of objects that remain in space for a long time gradually change due to the effects of solar activity and the gravity of surrounding celestial bodies. After the orbit changed over a period of a year and a half, the stage collided with the lunar surface at around 15:35 Japan time on August 5, 2026.
The impact site was photographed on August 11, 2026, by NASA's Lunar Reconnaissance Orbiter (LRO) using its onboard LROC camera. The resulting crater is about 18 meters in diameter and less than 3 meters deep. Rather than being circular, it has a V-shaped bright ejecta pattern spreading toward the south. This is because the object struck at a shallow angle of about 31 degrees from horizontal. If it had fallen straight down, the ejecta would spread in concentric circles, but at a shallow angle, the resulting pattern is skewed toward the direction of travel. The shape of the mark reveals the direction and angle of impact.
Images previously taken of the same region by South Korea's lunar orbiter "Danuri" (KPLO) also helped pinpoint the location. Comparing images from before and after the impact confirmed that this was newly formed terrain. The actual impact site fell within about 1 kilometer of the position NASA had predicted in advance.
Because the Moon has no atmosphere, there is no erosion from wind or rain. A mark like this one will remain for an extremely long time. While research is conducted to estimate the age of lunar terrain from the number of craters, a new crater made by an artificial object is also a valuable case in which the conditions at the moment of impact are known. A crater whose date, speed, angle, and mass of the impacting body are all known cannot normally be obtained from a natural meteorite.
At the same time, this is also a space debris problem. Rocket upper stages that have completed their role are, in the case of Earth orbit, typically disposed of by being burned up in the atmosphere, but stages placed on trajectories toward the Moon often remain in space as is. As in this case, they can sometimes collide with the Moon years later. Various countries plan to place probes on the lunar surface, and in the future, bases where people will stay. There is a growing need to keep track of what remains where.
Source: sorae, "SpaceX Falcon 9 Upper Stage Collides with Lunar Surface" (August 21, 2026)
https://sorae.info/space/20260821-f9-upper-stage-impact-site.html
Source: sorae.info