First color photograph of the Martian surface
Viking 1, the first probe to the Martian surface, to land and complete its mission successfully was launched August 20, 1975. It landed on July 20, 1976 on the western slope of Chryse Planitia (the Plains of Gold) and began transmitting about 25 seconds later.
It continued operating for about 6 years, the longest record until Opportunity broke the record on May 19, 2010. Contact was lost when a faulty command was sent from ground control to upload battery charging software but it overwrote data used by the antennae pointing software on November 11, 1982.