The spacecraft descended on parachutes, splashing down in calm Pacific waters near San Diego at 3:41 a.m. Eastern time (12:41 a.m. Pacific time). The capsule was hoisted out of the sea onto the deck of a SpaceX recovery ship and its hatch opened after 4 a.m., with the first of the returning astronauts exiting the capsule just before 4:30 a.m.

All four Crew 11 fliers looked healthy and in good spirits on a space-to-ground television broadcast of the change of command ceremony with no indication of which astronaut may have experienced the undisclosed medical issue that triggered Crew 11's early departure.

NASA says a crew member on the International Space Station is unwell. The agency canceled a planned spacewalk for Thursday and is taking the rare step of ending the Crew-11 mission early.

In a new study, terrestrial bacteria-infecting viruses were still able to infect their E. coli hosts in near-weightless "microgravity" conditions aboard the International Space Station, but the dynamics of virus-bacteria interactions differed from those observed on Earth.