Astronauts Butch Wilmore and Suni Williams will conduct a spacewalk outside the International Space Station to swab the orbiting lab for evidence of microorganisms.

NASA’s two stuck astronauts took their first spacewalk together Thursday, exiting the International Space Station almost eight months after moving in. Commander Suni Williams and Butch Wilmore removed a broken antenna and wiped the station’s exterior for evidence of any microbes that might still be alive after launching from Earth and escaping through vents.