This Thursday, astronauts Suni Williams and Butch Wilmore are set to embark on an exciting mission outside the International Space Station (ISS). Their task? To swab the exterior of the orbiting lab in search of microorganisms that might be hanging out in the harsh environment of space.

The spacewalk, scheduled to begin at 8 a.m. ET, will last roughly 6.5 hours. Fans of space exploration can tune in to NASA’s live stream on their website or YouTube channel from 6:30 a.m. ET to catch all the action.

Williams, sporting a white suit with red stripes, and Wilmore in an unmarked suit, will team up for this critical mission. This marks Williams’ ninth spacewalk and Wilmore’s fifth. Their to-do list includes removing outdated radio equipment and prepping a spare joint for the ISS’s robotic arm, Canadarm2, which helps move supplies and even astronauts during spacewalks.

The highlight of their outing, though, is the ISS External Microorganisms experiment. The pair will swab areas near life support vents to see if the station is shedding any tiny life forms into space. While spacecraft and suits are sterilized before missions, humans naturally carry microorganisms that could survive the process.

Understanding which microorganisms can endure the sterilization process and thrive in space is crucial. This knowledge could help refine cleaning procedures for future missions, like NASA’s planned return to the Moon and eventual trip to Mars.

The experiment could also reveal how far these microorganisms might travel in space. On Earth, organisms that survive in extreme environments—like deep-sea hydrothermal vents—are called “extremophiles.” Scientists are curious if similar hardy life forms can exist in the unforgiving conditions of space.

Williams and Wilmore’s stay on the ISS has been extended due to issues with Boeing’s Starliner spacecraft, which brought them there in June. Originally set to return after eight days, the astronauts are now scheduled to come back no earlier than late March aboard SpaceX’s Crew Dragon capsule.

Despite the delay, the astronauts remain upbeat. “It doesn’t feel like we’re castaways,” Williams said in a recent interview. “We have a lot to do while we’re up here.”

This spacewalk is just one of many exciting steps in humanity’s journey to explore the cosmos—and maybe even uncover the secrets of life beyond Earth.