Astronauts at the International Space Station Successfully Fixed Leaky Pump

The impromptu five-hour mission was completed ahead of schedule.

Astronauts Chris Cassidy and Tom Marshburn completed the most impromptu spacewalk in NASA history ahead of schedule. The two men spent roughly five hours outside of the International Space Station repairing an ammonia pump used to cool the laboratory's engine system. 

The ammonia pump was the chief suspect when little flecks were spotted leaving the ISS two days ago by commander Chris Hadfield. Cassidy and Marshburn only had two days to prepare for the spacewalk, a terrifyingly small amount of time considering they have to go out into space. But this is one of the emergency scenarios they were trained for before being posted to the ISS

NASA scientists on the ground walked the two men through the pain-staking process of replacing the pump Saturday morning. They stayed outside while the pump was activated to make sure no flecks were seen forming around the newly installed pump. "No evidence of any ammonia leakage whatsoever. We have an airtight system — at the moment," Mission Control reported. After about an hour of observation the two were brought back inside. It was a job well done. "No leaks! We're bringing Tom & Chris back inside," Hadfield tweeted

The emergency situation thankfully never put the astronauts life in danger, but it was a stressful way for Hadfield and Marshburn to spend their last few days on the ISS. The two return to earth in a Russian Soyuz spaceship on Monday.