Astronauts Barry Wilmore and Sunita Williams started their 17-hour journey home on Tuesday after months marooned on the International Space Station.
A SpaceX Dragon spacecraft carrying them, and Crew 9 mission members Nick Hague and Aleksandr Gorbunov, undocked from the orbiting laboratory and began the trip to the Earth at 5.05am GMT.
"They're on their way!" Nasa posted on X.
They were expected to splash down in the Gulf of Mexico near the Florida coast.
The Dragon spacecraft had flown four Crew 10 members from Florida’s Kennedy Space Center to the ISS on Sunday. Nasa astronauts Anne McClain and Nichole Ayers, Japan Aerospace Exploration Agency’s Takuya Onishi, and Kirill Peskov from Russia’s Roscosmos were expected to stay on the station for about six months.
Mr Wilmore and Ms Williams had lifted off to the ISS last June on what was supposed to be a routine test flight of Boeing's Starliner capsule to evaluate the spacecraft's capabilities.
They were scheduled to spend a week in space but technical problems forced their capsule to return without them, leaving them stranded with no way back home.
This was Ms Williams’ third trip to the space station. She spent 608 days in space across her stays, moving up to second on the list of the most experienced US astronauts.
Former astronaut Peggy Whitson spent about 675 days on the ISS over four flights.
The riskiest part of the crew’s journey back would be their reentry into the Earth’s atmosphere. The Dragon capsule would be moving 22 times the speed of sound during reentry and was likely to heat up to about 2,000C. It was expected to deploy two sets of parachutes to reduce its speed to under 32km per hour before splashing down.
Nasa said it would stream the capsule’s reentry and splashdown on its website as well as on X and YouTube.
Ms Williams and Mr Wilmore found themselves at the centre of a political storm with US president Donald Trump and his ally and SpaceX founder Elon Musk blaming the former Joe Biden Administration for leaving them high and dry on the ISS.
The astronauts refuted the narrative in interviews they provided from the space station. “That is been the rhetoric. That’s been the narrative from day one: stranded, abandoned, stuck – and I get it. We both get it,” Wilmore told CNN.
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