Astronauts are carrying out the last spacewalk of this mission to finish a clean and lube job that they began a week ago at the international space station. Spacewalkers Stephen Bowen and Shane Kimbrough will wrap up work on a jammed solar-wing rotary joint and, as a precaution, squirt extra grease on another joint that is working. Just before Monday's spacewalk began, NASA added a 16th day to space shuttle Endeavour's mission. Managers want to give the astronauts more time to fix a machine that's supposed to turn urine into drinking water. As the spacewalk is going on, astronauts inside will work on the machine. The water recycling equipment was delivered by Endeavour.