The Soyuz TMA-18M spacecraft is bringing American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko back to Earth after completing their mission at the International Space Station. Sergey Volkov is also returning to Earth with them. Kelly and Kornienko completed an ISS record year-long mission. The previous time a mission this long was completed on board the Russian Mir space station more than 20 years ago. Kelly participated in NASA's experiment on collecting valuable data on the effect of long duration weightlessness on the human body that will be used to formulate a human mission to Mars. After he comes back, NASA will compare his vital statistics with those of his twin brother.