MOSCOW (AP) — Two Russian crewmembers on the International Space Station ventured into open space Wednesday to conduct scientific research and help maintain the orbiting outpost. Oleg Kononenko and Alexey Ovchinin worked to retrieve several scientific experiments intended to study the impact of space flight that were mounted on the space station's exterior. They also cleaned some of the space station's windows, mounted handrails to facilitate future spacewalks and performed other maintenance. The spacewalk was scheduled to last 6½ hours, but the two managed to do the job quicker and wrapped up the mission in just over six hours. It was the fifth spacewalk for Kononenko and the first one for Ovchinin. Their crewmates — NASA's Anne McClain, Nick Hague and Christina Koch and David Saint-Jacques of the Canadian Space Agency — watched their progress from inside the orbiting outpost. Kononenko is set to return to Earth with McClain and Saint-Jacques next month following a 6 1/2-month stint in orbit. Ovchinin will replace him as the station's commander. For the spacewalk, the two attached stickers to their spacesuits paying tribute to Alexei Leonov, a legendary Russia cosmonaut who became the first human to walk in space on March 18, 1965. Speaking from the open space, they congratulated Leonov on his 85th birthday, which is coming Thursday.