Officials at NASA and SpaceX have announced that they will return four astronauts from the International Space Station to Earth earlier than planned due to an “unexpected medical issue” with one of the crew members.

The SpaceX Crew-11 astronauts had been due to return to Earth late next month, but on Jan. 8, NASA announced its decision to cut the mission short due to a “medical concern with a crew member currently living and working aboard the orbital laboratory.” The crew member, who was not identified due to medical privacy guidelines, is in stable condition, NASA said.

“It's not an emergent evacuation,” James Polk, NASA's chief medical officer, said at a news conference. “But we are erring on the side of caution for the crew member and in their best interest.”

When are they coming home?

The four astronauts — NASA’s Mike Fincke and Zena Cardman, Japan Aerospace Exploration Agency astronaut Kimiya Yui and Roscosmos cosmonaut Oleg Platonov — are scheduled to depart the ISS on the Dragon Endeavour capsule at 5 p.m. ET on Jan. 14 and are expected to splash down off the coast of California on Jan. 15 at approximately 3:40 a.m. ET.

“After performing a series of departure burns to move away from the space station, Dragon will conduct multiple orbit-lowering maneuvers, jettison the trunk, and re-enter Earth’s atmosphere for splashdown,” NASA said in an updated mission overview. The crew will be evaluated by NASA’s medical team upon their return.

It will be the first-ever medical evacuation of astronauts from the ISS. Russian cosmonauts Sergey Kud-Sverchkov and Sergei Mikaev and NASA astronaut Chris Williams will remain on board the ISS to complete their six-month mission, which began in November.

Fincke is expected to relinquish control of the ISS to Kud-Sverchkov in a change-of-command ceremony on Monday.

How is everyone doing?

In a post on LinkedIn, Fincke, who has served as the mission commander, said that everyone on the ISS is doing well.

“As many of you have heard, our crew will be coming home just a few weeks earlier than planned due to an unexpected medical issue,” Fincke wrote. “First and foremost, we are all OK. Everyone on board is stable, safe, and well cared for. This was a deliberate decision to allow the right medical evaluations to happen on the ground, where the full range of diagnostic capability exists. It’s the right call, even if it’s a bit bittersweet.”

Fincke shared an image of himself and the three other Crew-11 astronauts smiling and flashing heart symbols.

“This photo was taken as we prepared our space suits for return — a normal, methodical step in getting ready to come home, and a reminder that this decision was made calmly and carefully, with people at the center,” Fincke wrote. “We’re leaving the ISS in great hands. ... We’re grateful for the teamwork, proud of the mission, and looking forward to coming home soon — back to our loved ones and to resolving any medical questions with the best care available.”