A Russian and German astronaut, Scott Kelly and Mikhail Kornienko, respectively, began the first of 342 days aboard the International Space Station on Saturday, a mission about twice as long as usual. Kornienko and Kelly are accompanied by another Russian astronaut, Gennady Padalka, who will stay for six months. The mission marks NASA’s first attempt at a one-year- spaceflight; its goal is to study the effects of prolonged weightlessness on the human body, a potential step to a mission to Mars.
