When will the 'stranded' NASA astronauts return to Earth?

A pair of NASA astronauts stuck aboard the International Space Station (ISS) for more than nine months will return to Earth on Tuesday (March 18) at the earliest, NASA has said.

Astronauts Butch Wilmore and Suni Williams will depart the space station aboard a SpaceX Dragon capsule on Tuesday morning and splash down near Florida by the evening, if the weather permits.

Wilmore and Williams arrived at the ISS in June as part of Boeing's first Starliner Crew Test Flight. But a number of issues with Boeing's spacecraft — including five helium leaks and five failures of its reaction control system (RCS) thrusters — led to the mission being abandoned and the duo's time in space extended from eight days to nearly 300.

Their return, part of NASA's scheduled rotation between the ISS's Crew-9 and Crew-10 missions, was originally scheduled for Wednesday (March 19), but has been bumped forward to 5:57 pm ET on Tuesday (March 18) due to favorable weather conditions, according to NASA.

"The updated return target continues to allow the space station crew members time to complete handover duties while providing operational flexibility ahead of less favorable weather conditions expected for later in the week," NASA wrote in an announcement on Sunday (March 16).

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If everything goes according to plan, Wilmore and Williams will ride home on the Crew-9 Dragon capsule, called "Freedom", alongside fellow NASA astronaut Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov — half of the usual Crew-9 crew to allow space for the Starliner duo.

The Starliner astronauts' 300 consecutive days in space is nowhere near the current record of 437 days set by Russian Cosmonaut Valeri Polyakov in 1995, but it's still a long, and completely unexpected extension of the astronauts' shift aboard the ISS.

And it's also one that can have deleterious effects on the human body, causing the heart, bones and muscles to shrink over time under low gravity. These are well known side effects of long-term spaceflight that all astronauts must face, and not related to the extension of Wilmore and Williams' mission. To mitigate them, the astronauts have been doing two hours of resistance and endurance training every day.

"Mission managers will continue monitoring weather conditions in the area, as Dragon's undocking depends on various factors, including spacecraft readiness, recovery team readiness, weather, sea states, and other factors," NASA wrote in its update. "NASA and SpaceX will confirm the specific splashdown location closer to the Crew-9 return."

For those who want to watch Wilmore and Williams on their return, NASA will stream the event beginning on Monday (March 17) at 10:45 p.m. ET as the hatches close between Freedom and the ISS. The stream will then resume two hours later for undocking, which is expected at 1:05 a.m. ET. Live coverage will resume in the evening when the astronauts begin to reenter Earth’s atmosphere, currently scheduled for 5:11 p.m. ET.