NASA astronauts landed safely back on Earth after a medical emergency forced them to head back early during a mission at the International Space Station.

NASA astronauts Zena Cardman and Mike Fincke landed off the coast of San Diego at 3:41 a.m., alongside Japanese astronaut Kimiya Yui and Russian cosmonaut Oleg Platonov. The landing marks the only time in the ISS’s 25 years that a mission has been cut short due to a medical emergency.