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.