Butch Wilmore, a fellow astronaut, stuck in space with Williams, revealed how gravity will be the biggest challenge when the two astronauts return home.

Astronaut Sunita Williams is preparing for a tough transition back to Earth's gravity, after her long mission on the International Space Station (ISS). Her fellow astronaut, Butch Wilmore, emphasized the challenges they will encounter on their return. "Gravity is really tough, and that's what we feel when we get back," Wilmore told CNN.

NASA on Friday confirmed that it has moved up the return of stranded astronauts Butch Wilmore and Sunita Williams to mid-March. Williams and Wilmore have been aboard the International Space Station (ISS) since September.