This screengrab from video provided by NASA TV shows the SpaceX Dragon departing from the ISS

Nasa began its first-ever medical evacuation from the International Space Station (ISS) on Wednesday, bringing back an astronaut in need of medical care along with three crewmates. The four astronauts, from the US, Russia, and Japan, are scheduled to splash down early Thursday morning in the Pacific near San Diego aboard a SpaceX capsule, cutting their mission short by over a month. “Our timing of this departure is unexpected,” Nasa astronaut Zena Cardman said before the return trip, “but what was not surprising to me was how well this crew came together as a family to help each other and just take care of each other.” Officials have not identified the astronaut requiring medical attention or revealed the specific health issues. Outgoing ISS commander Mike Fincke reassured that the astronaut is “stable, safe and well cared for,” noting that “this was a deliberate decision to allow the right medical evaluations to happen on the ground, where the full range of diagnostic capability exists.” Cardman, Fincke, Japan’s Kimiya Yui, and Russia’s Oleg Platonov were originally scheduled to remain on the station until late February. Nasa canceled a planned spacewalk on January 7 after the medical concern emerged and subsequently announced the crew’s early return. Officials emphasised that the health issue was unrelated to the spacewalk or other station operations and stressed that it was not an emergency situation. Nasa confirmed that standard splashdown and recovery procedures will be followed, with medical teams on hand aboard the Pacific recovery ship. It is not yet clear how soon all four astronauts will be flown from California to Houston, home of the Johnson Space Center.This was the first spaceflight for Cardman, a 38-year-old biologist and polar explorer, and Platonov, 39, a former Russian Air Force fighter pilot who had overcome a previous health issue that delayed his space debut. Fincke, 58, a retired Air Force colonel, and Yui, 55, a retired Japanese fighter pilot, were veteran space travelers. Fincke has spent more than 1½ years in orbit over four missions and conducted nine spacewalks, while Yui recently celebrated his 300th day in space across two missions. One US astronaut and two Russian cosmonauts remain aboard the ISS, just a month and a half into an eight-month mission that began with a Soyuz launch from Kazakhstan. Nasa and SpaceX are working to advance the launch of a replacement four-person crew from Florida, currently planned for mid-February.Nasa officials said it would have been riskier to leave the ailing astronaut in space for another month than to temporarily reduce the station crew by more than half. Until the next crew arrives, routine and emergency spacewalks, which require a two-person team with backup support, will be suspended. The medical evacuation marks the first major decision by Nasa’s new administrator, Jared Isaacman, who took office in December. “The health and the well-being of our astronauts is always and will be our highest priority,” Isaacman said when announcing the decision last week.Computer modeling had projected that a medical evacuation from the ISS would occur roughly once every three years, but Nasa had never faced such a situation in its 65-year history of human spaceflight. The Russians, however, have experienced similar events, including in 1985 when cosmonaut Vladimir Vasyutin returned early from Salyut 7 due to a serious illness.