Four astronauts are hours away from strapping into a spacecraft and departing the International Space Station about a month early after one of them experienced a health issue. The impending departure would mark the first time in the station's 25-year history that a crew on the orbital outpost has cut a mission short in order to be medically evacuated.

The four-person Crew-11 splashed down in the Pacific Ocean, concluding their ISS mission about a month earlier than planned.

In a post shared to social media earlier this week, outgoing space station commander Fincke said that the astronaut in need of medical care, who officials declined to identify, was “stable, safe and w...