On Aug. 5, a spent SpaceX Falcon 9 upper stage is expected to strike the moon near Einstein and Bell craters along the western lunar limb, creating an impact scientists say could produce a brief but visible debris plume.
What Happened
The upper stage is leftover from the Jan. 15, 2025 launch that carried Firefly's Blue Ghost-1 lander and ispace's Hakuto-R Mission 2 (Resilience) robotic lander to the moon. According to research published on the arXiv preprint server by William Jo, a graduate research assistant at the University of Texas at Austin, physics simulations predict the central ejecta spike could reach roughly 47 to over 60 miles (75 to 100 kilometers) in altitude. "Our calculations suggest the plume should be several orders of magnitude brighter than the dark-sky background for the first few minutes after impact," Jo told Space.com, though he cautioned that numbers are on the optimistic side and that actual outcomes may differ.
Why It Matters
A study led by Benjamin Fernando at Los Alamos National Laboratory found that maximum ballistic range of resolved particles from the impact would be slightly under 1,000 km. The researchers noted this distance is "far enough to be significant from the perspective of presenting a hazard to future astronauts or infrastructure across much of the lunar surface." The event also offers scientists a rare chance to calibrate ejecta-plume models against a real-world impact of a hollow, spacecraft-like body—distinctly different from natural asteroid or comet strikes. NASA's Lunar Reconnaissance Orbiter is planned to pass over the projected crash site about seven days before and after the impact.
The Bottom Line
Scientists say the Aug. 5 impact could be observable from ground- and space-based telescopes, though much remains uncertain. Jo emphasized that while observers may focus on the initial flash, the longer-lasting ejecta plume is where the most valuable scientific data lies.