NASA astronauts are returning to Earth after nine months in space. Experts have said a prolonged period in space can come with changes to human physiology and psychology.

Astronauts Butch Wilmore and Suni Williams were scheduled to return home last year before issues with Boeing’s spacecraft extended their stay.

Butch Wilmore and Suni Williams returned to Earth in a SpaceX capsule after technical problems left them extending their stay on the International Space Station.