As their colleagues on the ground signified the 40th anniversary of a man’s stepping onto the Moon’s surface, astronauts on the International Space Station tended to a more mundane task: fixing a toilet.

A pump on the recently installed toilet in the American laboratory, Destiny, broke Sunday, contaminating part of the system. The pump’s function was to inject chemicals that helped separate liquids from solid waste.

Col. Gennady I. Padalka, the station commander, and Frank De Winne, a flight engineer, replaced some of the parts, and the toilet was operational on Monday.

Image Dr. David A. Wolf worked on the end of the International Space Station's robotic arm on the external stowage platform on Monday. Credit... NASA TV, via Reuters

In the interim, the seven astronauts from the space shuttle Endeavour, which docked Friday, had to use the toilet on the shuttle while the six station crew members already aboard the station used a second toilet in the Russian module.