An errant SpaceX rocket is on a collision course with the moon, and astronomers are eagerly awaiting the chance to observe the impact in real-time. New simulations from a team at the University of Texas at Austin offer a glimpse of exactly what scientists might see when the crash occurs.The spacecraft is an upper stage of a Falcon 9 rocket, which launched in January 2025 to deliver two lunar landers—Firefly Aerospace's Blue Ghost and Japanese company ispace's Hakuto-R. After the lunar delivery, the upper stage was supposed to fall back to Earth and burn up in the atmosphere. Instead the object, which is about the height of a five-story building, went AWOL, entering into orbit around Earth at a similar distance as the moon, setting up an eventual collision with our natural satellite.Amateur astronomer Bill Gray, who first observed the stray rocket, predicts that the crash will occur at around 2:35 a.m. EDT. The impact is likely to hit close to the Einstein crater, according to Gray. Because it will appear on the very edge of the sunlit side of the moon as seen from our planet, Earthlings might get a glimpse of some of the ejecta plume—the cloud of dust and debris that the collision will create. The 10,800-pound piece of space junk will hit the moon at around 5,400 miles per hour and with similar energy to three tons of TNT.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.The new simulations from the University of Texas at Austin's Computational Fluid Physics Lab preview what the collision might look like as it happens.A simulation of a rocket impacting the surface of the moonComputational Fluid Physics Lab | The University of Texas at AustinHowever, Gray warned in a recent blog post that viewers will almost certainly not be able to see the actual collision. In a recent preprint paper co-authored by Gray, astronomers explained that detecting the impact flash will likely be challenging because of the probable crash location on the moon’s sunlit hemisphere. Indeed, no artificial or natural impact flashes have ever been seen on the lit surface of the moon, they write.Instead, scientists may be able to observe the aftermath. The plume of debris the spacecraft creates as it slams into the lunar surface could take minutes after the crash to rise far enough to become visible from the moon's limb (it's outer, visible edge), according to Gray.This simulation gives an idea of what that might look like.This collision simulation shows the moon's outer edge, or limbComputational Fluid Physics Lab | The University of Texas at AustinThis is not the first time a piece of space junk has hit the moon, and as more and more spacecraft launch into orbit and beyond, it is unlikely to be the last. Tracking such errant bits and pieces of hardware is difficult, but as NASA and other space agencies gear up to establish permanently staffed lunar bases, doing so will take on more urgency.It’s Time to Stand Up for ScienceIf you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.