NASA ordered its astronauts to take refuge inside a docked SpaceX Crew Dragon spacecraft and prepare for potential evacuation of the International Space Station, but the crew returned to normal operations shortly afterwardsBy Lee Billings edited by Clara MoskowitzThe Russian segment of the International Space Station can be seen in this 2021 photo. Chronic air leaks from Russian modules are of increasing concern for the station’s safety and longevity. NASAAstronauts on the International Space Station (ISS) briefly took shelter and prepared for a potential evacuation due to worsening air leaks from a Russian-built module, a NASA official said today.The leaks are thought to arise from microscopic cracks in the PrK transfer tunnel, a small vestibule attached to the aft end of the Zvezda Service Module, which leads to a docking port for cargo spacecraft. Zvezda was the first contribution to the ISS by Russia’s space agency, Roscosmos, and was installed in July 2000. Engineers first noticed the leaks in 2019, but despite multiple efforts across the years to seal them and identify their underlying cause they have remained a chronic problem. As the leaks have continued, the orbital habitat now loses on the order of a pound of air pressure per day.“Following new leaks, Roscosmos has elected to proceed with a more extensive repair operation on Friday, June 5,” said NASA spokesperson Bethany Stevens in a post on the X social media platform. “Out of an abundance of caution, NASA has directed all four of the agency’s SpaceX Crew-12 members and NASA astronaut Chris Williams to assume an elevated safety posture in the [SpaceX] Dragon spacecraft while the repair is underway.”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.At least three Crew-12 astronauts—NASA’s Jessica Meir and Jack Hathaway, the European Space Agency’s Sophie Adenot—sought refuge in docked Crew Dragon spacecraft alongside Williams. Crew-12 also includes Roscosmos’s Andrey Fedyaev, but it was unclear whether he also took shelter alongside his crewmates as directed. Fedyaev’s Russian colleagues Sergey Kud-Sverchkov and Sergey Mikayev remained outside of Dragon to address the situation.Shortly after the astronauts entered Dragon, officials at NASA’s Mission Control Center at the space agency’s Johnson Space Center radioed a directive for them to exit the “safe haven configuration,” noting that “our Russian colleagues have elected to perform measurements only today.”Stevens clarified her earlier remarks in a follow-up statement on X: “Roscosmos has paused Friday’s structural repair efforts inside the Zvezda service module transfer tunnel, known as PrK, as more measurements and data is assessed… We look forward to working with Roscosmos on a collaborative approach to address the leaks.”Despite the shelter order, which may have arisen from miscommunication between NASA and Roscosmos mission controllers, the astronauts were probably not in any imminent danger, says Jonathan McDowell, an astrophysicist and space-situational awareness consultant. Onboard air supplies could easily make up the ongoing losses from the leaks. Even so, he says the situation “is potentially extremely serious.”“The worry is that a small crack could suddenly get catastrophically bigger,” he says. “That's unlikely but not impossible, and that would risk loss of the station and crew.”The scare highlights ongoing concerns over the safety of the aging ISS, which has now been in orbit for more than a quarter century and is well beyond its intended design life. The leaking PrK tunnel has become one of the most significant issues on the station, with NASA officially elevating the problem to its highest category of concern in internal safety evaluations. Protocols are already in-place to address the leaks, with the hatch leading from Zvezda to the PrK transfer tunnel kept closed unless access to Zvezda is needed. When that hatch is opened, a corresponding hatch capping the U.S. sections of the ISS is closed, to limit any catastrophic decompression to Russia’s segment.NASA has announced plans to retire the ISS by 2030, with deorbiting planned to occur shortly thereafter, but various efforts to further extend the space station’s life are ongoing.Additional reporting by Meghan BartelsThis is a breaking news story and will be updated.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. 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