An eight-day mission has turned into a nine-month space stint for two NASA astronauts who are finally set to come home. But why have they been away for so long - and what are the effects of such a lengthy stay in space?

The return mission for two astronauts stuck in space has been hit with another delay, NASA said Wednesday, as a joint operation with SpaceX was canceled.

NASA and SpaceX on Friday launched a long-awaited crew to the International Space Station that will let them bring home U.S. astronauts Butch Wilmore and Suni Williams, who have been stuck on the orbital lab for nine months.

The return mission for two astronauts stuck in space has been hit with another delay, US space agency NASA said on Wednesday. The two crew members of the Starliner, US astronauts Barry Wilmore and Sunita Williams,

A launch pad problem prompted SpaceX to delay a flight to the International Space Station on Wednesday to replace NASA's two stuck astronauts.