Moon dust has settled after the body of a 4.5-ton SpaceX rocket crashed into the terrain near Einstein Crater on August 5. That impact site was photographed by South Korea’s lunar-orbiting Danuri spacecraft, as well as NASA’s Lunar Reconnaissance Orbiter (LRO). A Chinese commercial space debris monitoring satellite also reportedly tracked and recorded the 5,400 mph (8,690 kph) lunar impact. Wandering through space for more than a year, the Falcon 9’s leftover upper stage had sent Firefly Aerospace’s Blue Ghost-1 lander on its way back to the moon on Jan. 15, 2025. Also sent toward the moon on that flight was Hakuto-R Mission 2’s Resilience, a robotic lunar lander developed by Japanese company ispace. While the moon has regained its serenity, the implications of the uncontrolled collision continue to reverberate. Close encounter Interestingly, there was also the prospect of a too-close-for-comfort conjunction between the Falcon 9 upper stage and Danuri. “We realized around the end of June that there is a Falcon 9 upper stage approaching the moon, and we also knew it would be near Danuri,” Eunhyeuk Kim, principal investigator at the Korea Aerospace Research Institute (KARI), told Espacio.com. You might like There was enormous uncertainty in the upper stage’s predicted trajectory, Kim said, while orbit information from South Korea’s Danuri lunar orbiter was fairly accurate. “Therefore, we cannot neglect the probability of an upcoming and close encounter.” Before and after images of the impact site. (Image credit: KARI) Spacecraft maneuver However, in mid-July, the KARI/Danuri team performed a spacecraft maneuver in preparation for a near-total lunar eclipse on August 28, Kim said. In that eclipse, 96% of the Moon’s visible surface will pass through Earth’s dark threshold shadow. Kim said the orbiter maneuver brought a slight change in the phase of the spacecraft’s orbit, canceling the likely conjunction between the upper stage and Danuri. At the time of the Aug. 5 impact, Danuri was flying over the moon’s south polar area, far from the impact zone, Kim said. Illustration of the moon, with an arrow pointing to the impact site of the Falcon 9 upper stage on August 5, 2026. (Image credit: Bill Gray/Pluto Project) High-speed ejecta Dean Sladen is a quality manager and aerospace engineer in the UK for Accu Components, a high-precision manufacturing company. What to read next “As space agencies and private companies build permanent lunar infrastructure, uncontrolled rocket stages go from a minor annoyance to a tangible operational risk,” Sladen told Space.com. “A direct hit is obviously the worst-case scenario, but distant impacts also generate ground shaking and high-velocity ejections that can degrade sensitive equipment over time.” Sladen noted that lunar impacts have been a constant throughout history, with meteorites and comets bombarding the surface unhindered by an atmosphere. “Over the last 65 years, artificial objects have added a new dynamic to these events,” he added. Artist’s concept of astronauts working on the lunar surface. (Image credit: NASA) Real danger Even modest hardware impacts permanently alter the lunar landscape, Sladen said. Given the lack of a substantial atmosphere on the moon, there is no air resistance to slow down debris. Therefore, an impact launches high-velocity ejecta (fine regolith and rock fragments) across large distances at speeds similar to those of a bullet. “While this is not a major threat to isolated missions today, as we establish permanent lunar infrastructure, high-speed ejecta pose a genuine danger to surface habitats, solar arrays, and working astronauts,” Sladen said. To mitigate this problem, Sladen suggested that the industry will likely need designated impact zones or tightly controlled and specific deorbit protocols to ensure that spent hardware lands far from active facilities. “That said, man-made waste is only half of the equation,” Sladen continued. “Natural meteorites remain a constant background threat, and while massive natural impacts are rare, they impact at significantly higher velocities and carry much more energy,” Sladen said. “Controlling our own hardware is simply the part of the risk profile that we really have the power to manage.” Plume Detections Meanwhile, while the Falcon 9 impact was difficult to see from Earth, several observations of our planet reported the detection of sodium and lithium gas above the crash site. The Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile, for example, saw the consequences of the impact. ESO reported that a chemical signature of the impact was visible for five to 10 minutes, with a huge plume of lunar material churned up by the powerful hardware. “I’m happy that ESO recorded some evidence of this through the VLT, and Danuri found the exact location of the impact,” said William Jo, a graduate research assistant at the University of Texas, Austin, who ran some computer simulations before the impact. “What we’ve learned so far is that the plume was too faint to see against the bright lunar surface, and only a large observatory telescope could make out some parts against the dark sky, which is exactly what happened,” Jo told Space.com. “The column must have come up very high,” he said, “and I would like to know how high, or even if we can replicate the signals.” Targets of Opportunity “Telescopes are the best spacecraft,” said Elaina Hyde, director of the Allan I Carswell Observatory at York University in Canada. “We are always looking for ‘opportunity targets’ like this event.” Hyde hosted a live-streamed event, training the observatory at the collision site. However, they could not detect the impact. “The lunar collision was not in our regular research program, but when it occurred, we put it as a high priority item to watch for clear weather,” Hyde said. “Anything that happens quickly like this is often a target of opportunity, because you don’t have a lot of time to plan the observation.” “However, since it was not visible from our location in Toronto, our ‘null’ or non-detection may help limit estimates about the size of the dust plume and perhaps some of its properties,” Hyde said. (Image credit: Lowell Observatory) Response to the impact Also monitoring the lunar impact were observers using equipment from the Lowell Observatory in Arizona. These researchers were able to measure the impact response of the rocket stage, detecting a considerable plume of sodium and lithium gas that lasted between five and 10 minutes after impact, reported Carl Schmidt, assistant research professor at Boston University’s Center for Space Physics. Observers at the 4.3-meter Lowell Discovery Telescope (LDT) at Happy Jack. Arizona used a long-slit spectrograph to detect the plume. Graduate students at Boston University continue to analyze data obtained from the moon impact. Bright Lithium Plume “At LDT, we saw a plume of bright lithium from the rocket body and fainter sodium. [signature]probably from the surface itself,” Patrick Lierle of Boston University told Space.com. “The bright plume of lithium extends more than half of our field of view.” The LDT results are also attributed to Emma Lovett, a graduate student at Boston University. William Jo said he awaits the release of observational data on the impact before he and his colleagues can refine their lunar ejecta simulation model. “That data, combined with our simulations, could tell us things like the composition of the lunar material, the orientation of the impact hitting, etc.,” Jo said.
