– Xochielt Sanchez
Answer by Robert Frost:
"Can"? We don't know. Typically crew members stay for about six months. This March, however, we will launch an astronaut (Scott Kelly) and a cosmonaut (Mikhail Kornienko) that will stay there for a full year. By studying how they react in those second six months, we will gather more data that will help us understand how a two year journey to Mars will affect crew members. Both Scott and Mikhail have previously spent 6 months aboard ISS. Scott has a twin brother who is also an astronaut. He will be studied on the ground as a control.
The record for a single stay in space was made 20 years ago, aboard the space station Mir. Cosmonaut Valeri Polyakov was there for 437 days.