SpaceX scrubbed the launch of a relief crew on Wednesday night, delaying the handoff for NASA astronauts who have been awaiting a return trip to Earth.

The Crew-10 mission will send four astronauts to the space station to take over for Butch Wilmore and Suni Williams’ crew, finally allowing their return home.

NASA astronauts Butch Wilmore and Sunita Williams face potential long-term health issues after a nine-month space mission. They may experience irreversible physical damage due to microgravity, such as bone density loss and muscle atrophy,