that space station. >> we're taking a look at the dramatic picture. of course as you point out, this was a hastily arranged space walk. anything could go wrong because nasa's not used to taking chances like this. they normally rehearse and do space walks with lots of information. how did you know that there was actually a problem? how did they find that leak? >> reporter: it was crew members on board the international space station, about 255 miles above the earth, who sow what flakes floating by in space. looked like snowflakes. this was bits of ammonia that had frozen there. there have been problems with ammon ammonia, so of it surmised that could be the problem. the two astronauts really are prepared to hastily exit and make repairs. that is part of the training for anything like this which could go suddenly wrong. so there is training to respond to this. and also in houston, astronauts