Yesterday NASA reported that an ammonia leak had been discovered on the ISS. Astronauts Tom Marshburn and Chris Cassidy are embarking on an emergency spacewalk to fix the problem. NASA TV is broadcasting the walk live, and you can follow along on the somewhat safer journey past the break.
Update (3:54PM ET): Nasa has reported within the last or so that the faulty pump has been successfully replaced. The entire spacewalk took about six and half hours to complete, according to NASA's Twitter.