As their emergency-pod flew through space, the crew was running out of oxygen. They had no choice but to take the risk and go back to Earth. Earth was closer than Mars, but if they went back to Earth, they'd fail the Mars exploration mission, which was going to most likely get them fired. But they had no choice. They had to get back home. Maybe they could get supplies and restart the mission. They headed towards Earth. On their way, debris hit their pod, forcing them out. They flew out into space, with no way of getting home.