NASA is bringing the Crew-11 astronauts back to Earth early after one encountered a medical issue that could not be dealt with aboard the orbiting outpost.

On Wednesday, the astronauts were preparing for a spacewalk scheduled for Thursday. However, after the spacewalk was postponed due to a medical concern, NASA concluded by the end of Thursday that bringing the crew back to Earth early – likely within the next few days – was the safest option.

NASA protected the astronaut's privacy, declining to identify which of the four crew members was affected or specify the condition's nature. Officials said the astronaut's condition was stable, requiring no emergency deorbit, and was unrelated to International Space Station operations.

Crew-11 consists of NASA astronauts Zena Cardman and Michael Fincke, JAXA astronaut Kimiya Yui, and Roscosmos cosmonaut Oleg Platonov. Cardman and Fincke were due to perform the spacewalk.

"This is not an injury that occurred in the pursuit of operations," said NASA Chief Health and Medical Officer James Polk during a briefing.

Freshly appointed NASA Administrator Jared Isaacman said: "It's the end of the Crew-11 mission right now. They've achieved almost all of their mission objectives."

The early departure will reduce the ISS's crew to three, including one US astronaut. NASA and its partners will attempt to advance the launch of the Crew-12 mission.

NASA Associate Administrator Amit Kshatriya noted that the ISS has operated with three crew members before, though the station was smaller then. He said "the vehicle is very autonomous and robust."

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NASA astronaut Chris Williams will maintain US operations solo until Crew-12 arrives. Kshatriya said Williams is "trained to do every task that we could ask him to do on the vehicle," with many ISS payloads operated from the ground.

This marks the first medical evacuation in the ISS's 25-year crewed history. Polk said that analysis models indicate a medical evacuation is expected every three years. The ISS's medical facilities can diagnose and treat many conditions without early returns.

Yet the incident highlights deep-space mission risks. Controllers could retrieve this astronaut. However, on Mars missions or even long-duration lunar trips, that option might not exist. ®