Astronauts aboard the International Space Station will undertake a spacewalk Saturday morning to try to repair a leak in their cooling system.
The leak appears to be ammonia used in a power supply. It was spotted midmorning on Thursday. Commander Chris Hadfield reported seeing "a very steady stream of flakes or bits" floating away from the station. On the ground, mission control noticed a steady drop in ammonia levels on one of the station's eight power channels. The same channel had problems back in November of 2012.
Astronauts Chris Cassidy and Tom Marshburn will undertake the roughly six-hour space walk. They hope to be able to identify the source of the leak while ammonia snow is still dribbling out. They will also replace a pump that may be the cause of the problem.
The leak isn't dangerous, and for now, NASA says, power can rerouted. But if it isn't repaired, it could impact research, especially if the station experiences a problem in another of its power systems.
"If we have to be down one power system for a long period of time, that is a significant impact to us," says Mike Suffredini, the station's program manager.