An ailing astronaut returned to Earth with three others on Thursday, ending their space station mission more than a month early in NASA's first medical evacuation.

SpaceX guided the capsule to a middle-of-the-night splashdown in the Pacific near San Diego, less than 11 hours after the astronauts exited the International Space Station.

"It's so good to be home," said NASA astronaut Zena Cardman, the capsule commander.

It was an unexpected finish to a mission that began in August and left the orbiting lab with only one American and two Russians on board. NASA and SpaceX said they would try to move up the launch of a fresh crew of four; liftoff is currently targeted for mid-February.

Cardman and NASA's Mike Fincke were joined on the return by Japan's Kimiya Yui and Russia's Oleg Platonov. Officials have refused to identify the astronaut who developed the health problem last week or explain what happened, citing medical privacy.

While the astronaut was stable in orbit, NASA wanted them back on Earth as soon as possible to receive proper care and diagnostic testing. The entry and splashdown required no special changes or accommodations, officials said, and the recovery ship had its usual allotment of medical experts on board.

The astronauts will receive more in-depth medical checks at a local hospital before flying to their home base in Houston, NASA said. Platonov's return to Moscow was unclear.

The astronauts emerged from the capsule, one by one, after it was aboard the recovery ship. They were helped onto reclining cots and then whisked away for standard medical checks, waving to the cameras.

Jared Isaacman, the space agency's new administrator, watched the action from NASA's Mission Control in Houston.

NASA stressed repeatedly over the past week that this was not an emergency. The astronaut fell sick or was injured on Jan. 7, prompting NASA to call off the next day's spacewalk by Cardman and Fincke, and ultimately resulting in the early return. It was the first time NASA cut short a spaceflight for medical reasons. The Russians had done so decades ago.

The space station has gotten by with three astronauts before, sometimes even with just two. NASA said it will be unable to perform a spacewalk, even for an emergency, until the arrival of the next crew, which has two Americans, one French and one Russian astronaut.