Astronauts Mike Fincke and Greg Chamitoff completed a seven-hour, 24-minute spacewalk at 7:39 a.m. on May 27, NASA reported. The primary objectives for the spacewalk were accomplished, including stowing the 50-foot-long boom and adding a power and data grapple fixture to make it the Enhanced International Space Station Boom Assembly, available to extend the reach of the space station's robotic arm.

This was the final spacewalk conducted by space shuttle astronauts. It also was the last of the four spacewalks for the STS-134 mission, for a mission total of 28 hours, 44 minutes. At 5:02 a.m., Fincke and Chamitoff surpassed the 1,000th hour astronauts and cosmonauts have spent spacewalking in support of space station assembly and maintenance, the space agency said.

The milestone occurred four hours and 47 minutes into the spacewalk, the 159th in support of station assembly and maintenance, totaling 1,002 hours and 37 minutes. It was the 248th spacewalk U.S. astronauts have conducted and the 118th from space station airlocks.

It was Fincke's ninth spacewalk for a total time of 48 hours and 37 minutes; he is sixth on the all-time list. At about 8 p.m. on May 27, he will become the U.S. astronaut who has spent the most number of days in space, surpassing Peggy Whitson's record of 377 days in space. It was Chamitoff's second spacewalk for a total time of 13 hours and 43 minutes.

While the Endeavour crew wraps up its final spacewalk, NASA also announced it has ended operational planning activities for the Mars rover Spirit and transitioned the Mars Exploration Rover Project to a single-rover operation focused on Spirit's still-active twin, Opportunity.

Spirit last communicated on March 22, 2010, as Martian winter approached and the rover's solar-energy supply declined. The rover operated for more than six years after landing in January 2004 for what was planned as a three-month mission. NASA checked frequently in recent months for possible reawakening of Spirit as solar energy available to the rover increased during Martian spring. A series of additional re-contact attempts ended May 27, designed for various possible combinations of recoverable conditions.

"Our job was to wear these rovers out exploring, to leave no unutilized capability on the surface of Mars, and for Spirit, we have done that," said Mars Exploration Rover project manager John Callas of NASA's Jet Propulsion Laboratory (JPL).

The trove of data from Spirit could still yield future science revelations. Years of analysis of some 2005 observations by the rover's Alpha Particle X-ray Spectrometer, Miniature Thermal Emission Spectrometer and Moessbauer Spectrometer produced a report last year that an outcrop on Husband Hill bears a high concentration of carbonate. Steve Squyres of Cornell University, principal investigator for Spirit and Opportunity, said this is evidence of a wet, non-acidic ancient environment that may have been favorable for microbial life.

"What's most remarkable to me about Spirit's mission is just how extensive her accomplishments became," said Squyres. "What we initially conceived as a fairly simple geologic experiment on Mars ultimately turned into humanity's first real overland expedition across another planet. Spirit explored just as we would have, seeing a distant hill, climbing it and showing us the vista from the summit. And she did it in a way that allowed everyone on Earth to be part of the adventure."