NASA ISS Astronauts' Emergency EVA appears Successful in fixing Coolant Leak

In this Saturday, May 11, 2013 photo made available by NASA, astronaut Chris Cassidy and Tom Marshburn, not pictured, perform a space walk to inspect and replace a pump controller box on the International Space Station after an ammonia coolant leak was discovered. 

Credit: NASA

NASA says an impromptu spacewalk seems to have fixed a big ammonia leak at the International Space Station.

The "gusher" erupted last Thursday. Two days later, spacewalking astronauts replaced a suspect ammonia pump. NASA is now calling the old, removed pump "Mr. Leaky."

On Thursday, a Mission Control official said the spacewalking repairs definitely took care of the big leak.

Engineers don't know whether the pump replacement also took care of a smaller leak that has plagued the system for years.

It will take at least a couple months of monitoring to know the full status. Ammonia is used as a coolant in the space station's radiator system.

The leak forced one of the station's seven power channels to go offline. NASA hopes to resume normal operations early next week.