A four-ton SpaceX Falcon 9 upper stage left drifting after a 2025 lunar mission is expected to crash into the Moon at about 5,400 mph, likely striking Einstein Crater. The impact should occur at approximately 2:35 a.m. ET (0635GMT). Reuters reports: Such stages typically fall back into Earth's atmosphere and burn up or plunge into the ocean after boosting the rocket's payload to a precise spot in orbit. But because the January lunar lander mission required more thrust than missions closer to Earth, the rocket's second stage remained in space, floating aimlessly among thousands of other pieces of space junk that active satellites must steer clear of. It was not until earlier this year that astronomers determined that the rocket stage, which had dumped its remaining fuel and cannot be controlled, was on an orbital trajectory ending at the moon. "What has happened is essentially a mixture of solar activity and gravity forces have put it on a path toward the moon," Julianna Scheiman, SpaceX director of NASA science and Dragon programs, told reporters on Monday. "This may be of some -- probably minor -- scientific interest, and we may learn some things from it," said Bill Gray, creator of widely used astronomy software who published a report on the stage's impact in April. "It doesn't present any danger to anyone, though it does highlight a certain carelessness about how leftover space hardware (space junk) is disposed of." You can try to watch the impact via a livestream on YouTube; however, the area it's expected to hit (Einstein Crater) is on the moon's western limb, "which is often difficult to see from Earth," notes Reuters. It will also likely "kick up a plume of lunar dust that will likely be illuminated by sunlight but difficult to spot with the naked eye from Earth."

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"Space.com and The Guardian are reporting that the Falcon 9 upper stage leftover from the launch of the Firefly Blue Ghost-1 lander on Jan. 15, 2025 is due to impact the Moon on Aug. 5, 2026," writes longtime Slashdot reader fahrbot-bot. From a report: Onboard the same flight was the Hakuto-R Mission 2, called Resilience, a robotic lunar lander developed by the Japanese company ispace. According to a new study by an international team, the resulting impact plume may briefly be bright enough to see against the dark sky near the moon's edge. That means it might be visible to moongazers with sufficiently sensitive telescopes. This head-on collision of the errant stage is expected to occur near the Einstein and Bell craters near the western lunar limb. It may well be visible to ground and space-based assets. Using special physics simulations to model the impact, William Jo, a graduate research assistant at the University of Texas, Austin and colleagues predict the debris plume from the impact will have the central ejecta spike reaching roughly 47 miles to over 60 miles (75 kilometers to 100 kilometers) 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. "So the plume should be visible, though I'd stress this is a single nominal case. The real one will look different, and the numbers are on the optimistic side. But the point worth making is that the flash isn't really the story here." Jo emphasized that there's great slam-dunk science to be had. "Watching this one gives us a rare chance to open up ejecta-plume science and calibrate those models against a real event, which matters for every future thing we deliver to the moon," Jo said.

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