NASA evacuates ISS for first time in 25 years amid mystery astronaut illness

The four returning astronauts are aiming for an early Thursday morning splashdown in the Pacific near San Diego with SpaceX.

The returning crew includes commander Mike Fincke, flight engineer Zena Cardman, Japanese astronaut Kimiya Yui and Russian cosmonaut Oleg Platonov.

The decision cuts short their mission by more than a month.

The unidentified crew member was taken ill last week and the American space agency announced it would cut short the current Crew 11 mission so they can be seen by medical professionals on Earth.

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"Our timing of this departure is unexpected," NASA astronaut Zena Cardman said before the return trip, "but what was not surprising to me was how well this crew came together as a family to help each other and just take care of each other."

Officials refused to identify the astronaut who needed care last week and would not divulge the health concerns.

The ailing astronaut is "stable, safe and well cared for", outgoing space station commander Mike Fincke said earlier this week via social media.

"This was a deliberate decision to allow the right medical evaluations to happen on the ground, where the full range of diagnostic capability exists," he said.

The crew member is said to be stable, and the end to the mission is not being described as an emergency evacuation.

NASA Chief Health and Medical Officer Dr. James D. Polk said in a press conference last week that the ISS is equipped with a "robust suite of medical hardware," but it is lacking tools needed to complete a full overview of the astronauts condition.

He added that the medical issue has risen to the level where NASA would prefer to "complete that workup on the ground."