HOUSTON — Two astronauts ventured outside Friday for the last spacewalk of the shuttle Atlantis' mission to the international space station, working to attach science experiments to the exterior of the new Columbus lab.

Spacewalkers Rex Walheim and Stanley Love floated out of the hatch as the space station passed over the Pacific Ocean west of southern Chile.

They were scheduled to spend about 6 1/2 hours installing the experiments, retrieving an old space station gyroscope and, if there is time, examining a tiny chip on a handrail near the spacewalk hatch and a jammed solar rotary joint.

The first piece of equipment that Walheim and Love installed is an observatory to monitor the sun.

Love pulled the experiment module out of the shuttle's cargo pay and held onto it while catching a ride on the station's robotic arm to the outside of Columbus. The spacewalkers then bolted the module down.

"Nice work you guys," Mission Control radioed after they finished that task.

The other equipment, to be installed later Friday, will carry several experiments requiring exposure to the uniquely harsh environment of space.

Once those are attached to Columbus and the gyroscope is stowed in the shuttle's cargo bay, the spacewalkers hope to turn their attention to two trouble spots on the station.

The chip — discovered by Love during Monday's spacewalk and thus dubbed Love Crater — is the apparent result of a micrometeorite strike. It may be where spacewalking astronauts have torn their gloves over the past year or so. To find out, Walheim and Love will run a spare glove over the hole to see if the material snags.

The pair also hopes to have time to inspect the rotary joint, which is needed to turn one of the space station's two sets of huge solar wings. Spacewalkers have peered inside several times since the joint broke last fall, but NASA is still trying to determine what is causing the metal parts to grind, clogging the joint with shavings.

While the spacewalkers are outside, other crew members will continue working inside Columbus to get the lab ready to produce science in the coming days.

The astronauts awoke Friday to a song by German Drafi Deutscher whose title, NASA said, translates to "Marble Breaks and Iron Bends." German astronaut Hans Schlegel said the tune, popular in his youth, talks about finding one great love.

"I'm very fortunate that I found that in my wife, Heike," he said.

Atlantis is scheduled to undock from the space station on Monday and land in Florida on Wednesday.