Astronaut Scott Kelly Completes His First Space Walk

— -- Mission accomplished.

Commander Scott Kelly and his American co-worker, Dr. Kjell Lindgren, completed their first-ever space walk today lasting seven hours and 16 minutes as they completed a series of upgrades to the outside of the International Space Station, NASA officials said.

First up was the installation of a thermal cover on the station's Alpha Magnetic Spectrometer, which is a particle physics detector.

They also greased the space station's robotic Canadarm2, which has previously been used to grab SpaceX's Dragon capsule on cargo resupply missions. The astronauts finished up their first space walk by routing several cables to prepare new parking spots for future U.S. commercial crew spacecraft.

The space walk is the 189th to happen at the International Space Station and NASA's 32nd to service the low-Earth orbit outpost, according to the space agency.

Lindgren arrived in space in July, marking the flight engineer's first trip.

Kelly is currently halfway through a year-long stay at the International Space Station and on Thursday will become the U.S. astronaut who has lived in space the longest during a single U.S. spaceflight, according to NASA.

Kelly is participating in a study along with his twin, former astronaut Mark Kelly, about the long-term effects on humans in space. The implications of the study are expected to help NASA better prepare for one day sending humans to Mars.