Viking 1
Viking 1 was the first of two spacecraft sent to Mars as part of NASA's Viking program, landing on July 20, 1976. It was the first successful Mars lander in history. Viking 1 was operational on Mars for 2245 sols. Viking 1 held the record for the longest Mars surface mission of 2307 days or 2245 Martian solar days, until that record was broken by the Opportunity rover on May 19, 2010.