The US National Aeronautics and Space Administration (NASA) on Monday celebrates the first anniversary of its rover Spirit's landing on the Mars on Jan. 3, 2004. (Xinhua/Reuters)

    PASADENA, California, Jan. 3 (Xinhuanet) -- The US National Aeronautics and Space Administration (NASA) on Monday celebrated the first anniversary of its rover Spirit's landing on the Mars on Jan. 3, 2004.

Both Spirit and another NASA rover Opportunity, which landed on the Mars on Jan. 24, 2004, successfully completed their three-month primary missions in April. (Xinhua Photo/File)

    Both Spirit and another NASA rover Opportunity, which landed on the Mars on Jan. 24, 2004, had successfully completed their three-month primary missions in April. The unanticipated longevity allows the two rovers to keep working on the red planet.

    "Little did we know a year ago that we'd be celebrating a year of roving on the Mars. The success of both rovers is tribute to hundreds of talented men and women who have put their knowledge and labor into this team effort," NASA's Jet Propulsion Laboratory(JPL) Director Charles Elachi told a press briefing here.

    After the worst of the Martian winter, the twin rovers are in "amazingly good" shape, and both are strong enough to continue exploring, scientists with the JPL said.

    Spirit is exploring the Columbia Hills within the Gusev Crater on the Mars after it discovered a new type of rock in December, while Opportunity is driving toward the heat shield that protectedit during descent through the Martian atmosphere.

    Scientists hope to determine how deeply the atmospheric friction burnt the protective layer. These findings may help improve the ability to deliver future vehicles to the Mars or other planets.

    NASA's next Mars mission, the Mars Reconnaissance Orbiter, is due to launch in August, said the JPL, which has managed the Mars Exploration Rover project since 2000. Enditem