BEIJING, April 27 (Xinhuanet) -- The second of NASA's twin Mars rovers has wrapped up its primary mission, on its 90th full day on the Red Planet.

    Opportunity and its twin, Spirit, have completed all the tasks NASA required before the space agency would consider the double mission a success.

    Opportunity will probably keep working through at least September, while Spirit is already well into its own extended mission.

    Each of the identical rovers have travelled at least 594m, took stereo and color panoramas of their surroundings, drove to at least eight locations and operated simultaneously with its twin for 60 days.

    The goal of the double mission is to scour Mars for geologic evidence the planet once was a wetter place capable of sustaining life. Opportunity has found that evidence.

    On the opposite side of Mars, Spirit has found evidence of only limited amounts of past moisture.

    (CRIENGLISH.com)