Watch NASA's Emergency ISS Spacewalk Live Right Now (Updating)

Two days ago, astronauts on the ISS discovered some little white flakes suspiciously floating away from the station. And now, they're already floating outside in zero gravity to fix it. From planning to go-time, this has been the most impromptu spacewalk in NASA history, and you can tune in below.

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The goal of the jaunt is to fix the liquid ammonia cooling system needed to power one of the station's solar arrays. It's not a life or death situation fortunately, but it's a big enough deal to get to astronauts out to fix it, pronto.

So far, mission control has been painstakingly walking astronauts Chris Cassidy and Tom Marshburn through the process step by step by step by step, since there was no time to really brief them on the walk beforehand. This is one of the types of emergencies astronauts prepare for, so this should go off without a hitch, but there's about 6.5 hours of work to be done. When all is said and done, there's going to be some well-deserved sleeping going on in orbit. [NASA]

Update: Just 2.5 hours in and the busted pump has been successfully replaced.

Update 2: The pump is up and running, and now pumping ammonia. So far, everything's going fine, but we won't know if everything is definitely fixed for sure until its had a chance to work for a while.

Update 3: The astronauts are undergoing a "bake-out" and letting the sun get any excess ammonia off them before they head back inside.

Update 4: They're headed back towards the airlock now.

Update 5: Looks like mission accomplished; everyone is back inside.