Two American astronauts and a Russian cosmonaut return to earth wrapping up a six-month mission at the International Space Station as tensions between Washington and Moscow threaten a rare area of cooperation. NASA astronauts Drew Feustel and Ricky Arnold and Oleg Artemyev of Roscosmos touched down on steppe land southeast of the Kazakh town of Dzhezkazgan at the expected time of 1145 GMT.