As a nearly five-hour spacewalk Saturday morning drew to a close, the two astronauts replaced a suspected faulty pump in an effort to fix an ammonia coolant leak on the International Space Station.
Astronauts Thomas Marshburn and Christopher Cassidy began their spacewalk at 8:44 a.m. Saturday. The two successfully replaced a 60-pound pump box which NASA suspected was the source of the leaking ammonia coolant. They found no evidence of the frozen ammonia flakes that had originally led them to the pump box. The astronauts also found no evidence of damage to the pump box.