A SpaceX capsule has departed the International Space Station carrying a four-member crew on an emergency return flight to Earth necessitated by an unspecified serious medical condition afflicting one of the astronauts aboard.
The Crew Dragon capsule, which is carrying two US NASA astronauts, a Japanese crewmate and a Russian cosmonaut, undocked from the space station and began its descent from orbit about 9:20am AEDT (2220 GMT).
NASA astronauts Mike Fincke and Zena Cardman, Roscosmos cosmonaut Oleg Platonov, and JAXA (Japan Aerospace Exploration Agency) astronaut Kimiya Yui are headed for a splashdown in the Pacific Ocean off the California coast early on Thursday, local time.
Live video from a NASA webcast of the departure showed the capsule separating from the ISS and drifting away from the orbiting laboratory as the two vehicles soared some 418 kilometres over the Earth, south of Australia.
The astronauts were seen strapped into the Crew Dragon cabin, seated side by side and wearing their helmeted white and black space suits as the undocking proceeded.
The plan to bring all four members of Crew-11 home a few weeks ahead of schedule was announced January 8, with NASA Administrator Jared Isaacman saying one of the astronauts faced a "serious medical condition" that required immediate medical attention on the ground.
NASA officials have not identified which of the four crew members was experiencing a medical issue or described its nature, citing privacy concerns.
The crew arrived at the space station after a launch to orbit from Florida in August.
Mr Fincke, the station's designated commander, and Ms Cardman, assigned as flight engineer, had been scheduled to conduct a six-hour-plus spacewalk last week to install hardware outside the station.
The spacewalk was cancelled on January 7 over what NASA then characterised as a "medical concern" with an astronaut.
NASA Chief Health and Medical Officer James Polk later said the medical emergency did not involve "an injury that occurred in the pursuit of operations".
If all goes as planned, the splashdown will conclude what ended up being a 167-day mission.
Reuters