Two American astronauts have successfully removed a damaged pump on the International Space Station ahead of schedule.

Rick Mastracchio and Michael Hopkins began repairing the bad valve during a spacewalk on Saturday.

Mastracchio, who holds the record for spacewalks, called it “exciting” but also challenging. There was a brief scare when he reported a steady stream of ammonia leaking out of the pump and said some flakes brushed against his suit.

The pump will be replaced on Monday.