When astronauts Suni Williams and Butch Wilmore left Earth for the International Space Station two months ago, they left behind their bags for a critical piece of equipment. They were leading the first crewed test flight of Boeing's Starliner spacecraft, and they left without their own toiletries and other personal comforts - expecting to return to Earth within a week or so.
They have now been on the space station for more than 60 days, and NASA this week raised the possibility that they could remain there until early 2025 due to ongoing problems with their Starliner capsule.
Such an extension is not certain, as NASA officials hope to resolve some disagreements within the space agency over Starliner's safety. NASA said a decision should be made in mid-August.
However, NASA indicated that a months-long extension may be necessary if Starliner proves unsafe and they have to fall back on Plan B, with the astronauts returning home aboard a SpaceX Crew Dragon capsule instead.
What exactly would Williams and Wilmore do during the next six months in space?
Currently, the two are guests. They are not part of Expedition 71, the international crew of seven astronauts who serve as the official staff of the space station. However, NASA has said they have seamlessly integrated with the group and have taken up daily duties aboard the space laboratory.
But if their stay is extended through February, as NASA has indicated if Starliner can't bring them home, Williams and Wilmore would become full-time members of the expedition crew.
They would perform typical crew duties, such as conducting spacewalks outside the space station, maintaining the space laboratory and carrying out a tight schedule of scientific experiments.
And NASA confirmed that the Starliner astronauts are ready for such a transition.
"A few years ago we made the decision - knowing this was a test flight - to make sure we had the right resources, supplies and training for the crew, in case for some reason they needed to stay on the ISS for an extended period of time," Dana Weigel, NASA's manager of the International Space Station Program, said during a briefing on Wednesday.
"Butch and Suni are fully trained," Weigel added. "They're capable and up to date with EVA (spacewalks), with robotics, with all the things we expect them to do."
Joining Crew-9
Nothing is certain, but NASA indicated for the first time on Wednesday that it is considering flying the Boeing Starliner spacecraft home empty.
But that wouldn't leave Williams and Wilmore in space indefinitely. They would get a ride home on SpaceX's Crew-9 mission.
Crew 9 - a routine trip to the space station to replenish the expedition crew - will currently fly with four astronauts: NASA astronauts Zena Cardman, Nick Hague and Stephanie Wilson and cosmonaut Aleksandr Gorbunov of the Russian space agency Roscosmos.
Under NASA's contingency plan for Starliner, two of those astronauts were to be ejected from the mission, though authorities did not disclose which of the four crew members those would be.
The Crew Dragon spacecraft would then fly to the International Space Station with two empty seats, departing no earlier than Sept. 24, based on the most recent data shared by NASA.
Ballast, or pieces of metal that served as dead weight, would fly next to the two empty seats in Crew-9 to maintain the Crew Dragon's center of gravity.
The two Crew 9 astronauts would then join Williams and Wilmore aboard the space station. Together, they would complete the cast of Expedition 72. Additional Russian cosmonauts will also join the expedition. The expedition is scheduled to launch in September after a handover period.
As is customary for missions to the space station that tie in with an expedition, the Crew 9 astronauts will stay on board for about five or six months. Williams and Wilmore will therefore remain in space for another six months, in addition to the two months they have already spent in space.
Once they become part of Crew-9, they are put into a structured schedule, with their days planned hour by hour.
Olympic Games in orbit around the Earth
The astronauts have already gotten into some of that daily work. According to recent updates from NASA, Williams and Wilmore have spent their time so far maintaining the space station, inspecting hardware, organizing cargo, performing checks on Starliner, and assisting with science experiments and technical demonstrations.
Williams and Wilmore have had chances to have some fun in microgravity, though. NASA shared footage July 26 of the astronauts passing around a plastic flashlight on the space station and simulating Olympic events, including discus throwing and pommel horse riding. (Exercising is a key task for astronauts to avoid losing too much muscle and bone density in space.)
Williams has already proven that she is an excellent space athlete.
In 2012, during a previous trip to the International Space Station, she became the first person to complete a triathlon in space. Williams used a stationary bike, simulated swimming on a weightlifting machine and ran on a treadmill while strapped in with a harness to keep her from floating away.
She achieved this feat after running the Boston Marathon from the space station in 2007.
Williams and Wilmore spent 500 days in space together before flying the Starliner test flight. Williams said she even cried after leaving the space station after her last mission in 2012, unsure if she would ever return.
"This flight is a dream for her," a NASA commentator said during a livestream of the Starliner launch on June 5.
Long-term stay in space
It often happens that astronauts unexpectedly extend their stay on board the space station: by days, weeks or even months.
For example, NASA astronaut Frank Rubio was scheduled to spend about six months aboard the International Space Station for his first trip to low-Earth orbit, set to launch in September 2022. Instead, he spent 371 days in space after a coolant leak was discovered from his original flight - a Russian Soyuz capsule - while docked to the space station.
Rubio's year-long stay earned him an American record for the longest consecutive number of days in space.
Astronauts also regularly stay on the space station for days longer due to a variety of factors, such as bad weather on Earth or other changes in planning.
Without suitcase
Flying to the space station without the bags they'd packed for their mission may have complicated the comforts of the Starliner astronauts' extended stay. NASA decided to unload their luggage from the spacecraft to make room for a much-needed pump to repair a malfunctioning toilet aboard the space station.
The two astronauts may finally have a reprieve after a Northrop Grumman cargo mission arrived at the space station on Tuesday.
"We like to keep our options open, so we do have some supplies like clothing ... some personal food for (Williams and Wilmore), things like that," Bill Spetch, NASA's operations integration manager for the International Space Station Program, said during a news conference last week.
And there's no indication that food supplies will be running low anytime soon. Packed alongside the Northrop Grumman ship's 8,200 pounds of science experiments and cargo was a food shipment of meals and produce such as squash, radishes, carrots, blueberries, oranges, apples and coffee, Spetch said.
Still, NASA must make a quick decision about whether to bring Williams and Wilmore back or integrate them into the normal crew rotation, because the space station's food supplies and other resources are not unlimited.
"While they're out there, we have extra crew, we have extra hands, and they can do a lot more work. But they're also using more consumables, more supplies," Ken Bowersox, NASA's associate administrator for the Space Operations Mission Directorate, said Wednesday.
"At some point," he added, "we have to bring those people home and get back to a normal crew size on the ISS."
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