The International Space Station Is Leaking Coolant

NASASunlight glints off the International Space Station with the blue limb of Earth providing a dramatic backdrop in this photo taken by an astronaut on the shuttle Endeavour just before it docked after midnight on Feb. 10, 2010 during the STS-130 mission.White flakes floating across your window would be a welcome sight for a kid on Christmas, but on Thursday it was a dangerous warning sign for astronauts aboard the International Space Station.

The white flakes were caused by an ammonia leak. The ammonia serves as a coolant for the station's solar arrays. The astronauts aren't in any immediate danger.

The leak is coming from the array's P6 truss structure, and seems to be in the same vicinity of a leak that the crew tried to repair back in November, though it's hard to tell without going out and taking a look at the problem.

The amount of ammonia leaking seems to be getting worse based on the video feed, though that could also be a factor of the station's orientation with the sun. Here's an image of some of the flakes — the white fluffy looking dots in on the black emptiness of space — which do surprisingly look a lot like snow:

NASA TV

The leak doesn't put the crew in danger, but a portion of the solar arrays are turned off and not supplying power that is essential to running the station. NASA is rerouting electricity from the other arrays to keep the station fully functional, according to a press release.

To repair the leak, astronauts Chris Cassidy and Tom Marshburn are prepping to go on an emergency space walk on Saturday. NASA won't decide to go ahead with the extravehicular activity until late Friday.

See the leak in action, and hear Commander Chris Hadfield talking to mission control about the leak in this NASA TV video: