Astronauts have found metal shavings inside a joint needed to turn a set of solar power panels on the International Space Station.
The metal shavings were found when two astronauts from the space shuttle Discovery successfully completed the mission's second space walk.
Astronauts Scott Parazynski and Daniel Tani began their 6.5-hour jaunt early Sunday morning.
Tani was charged with inspecting the balky rotary joint for the station's solar wings and checked for possible sharp edges on a rail for the robotic arm.
While no sharp edges were found on the robotic arm railings, Tani noticed "metal shavings and unusual wear on a race ring," NASA's website reported.
"It's quite clear that it's metal-to-metal grating or something, and it's widespread,'' Tani said.
"Wow,'' said his spacewalking partner, Scott Parazynski.
NASA officials say the joint has been showing increased signs of friction recently.
The spacewalkers' other tasks included preparing an 18-tonne truss to for relocation and adding to equipment on the station's newly-installed module, Harmony.
The pair unbolted the cords that held the massive truss to the top of the station. Astronauts Stephanie Wilson and Doug Wheelock used the Canadarm 2 to detach the truss and move the solar array section to a temporary holding position for the night.
"Don't drop it!'' one of the spacewalkers joked.
Installation will take place during a third spacewalk scheduled for Thursday.
Parazynski also installed spacewalking handrails and other equipment to the outside of Harmony. Space shuttle Discovery delivered the school-bus sized compartment. The astronauts installed it during their first space walk.
Grapple fixtures were added to the module that will enable the Canadarm 2 to move the compartment from its current temporary location to its permanent home on the front of the Destiny laboratory.
The Italian-built, multi-port module will serve as the docking port for European and Japanese laboratories that are scheduled for launch in December. The installation of the new compartment will serve to effectively double the amount of laboratory space on the station.
The module will function as a central hub on the station, providing air, electricity and water for the crew. It was launched with sophisticated computer and electronic equipment pre-installed that was later tightly bolted down for the jarring trip to the space station.
The crew first entered Harmony on Saturday to collect air samples.
On Saturday, NASA officials decided against another inspection of shuttle Discovery's thermal shield, deeming it in good condition after Tuesday's launch.
