The two astronauts have been on at the International Space Station since last June after the ship they arrived in experienced helium leaks and thruster issues, requiring a new ship for the ride back to Earth.

“Future built environments, including space stations, could benefit from intentionally fostering diverse microbial communities that better mimic the natural microbial exposures experienced on Earth, rather than relying on highly sanitized spaces,” says co-first author Rodolfo Salido at UC San Diego.

A launch pad problem prompted SpaceX to delay a flight to the International Space Station on Wednesday to replace NASA’s two stuck astronauts . The new crew needs to get to the International Space Station before Butch Wilmore and Suni Williams can head home after nine months in orbit.

NASA and SpaceX on Wednesday delayed the launch of a replacement crew of four astronauts to the International Space Station that would have set in motion the long-awaited homecoming of U.S. astronauts Butch Wilmore and Suni Williams.