NASA’s Viking 1 became the first successful lander to reach Mars.
Viking 1 launched on 20 August 1975 and entered Mars orbit on 19 June 1976. Its lander touched down in Chryse Planitia on 20 July 1976, while the orbiter photographed the planet and helped select and support the landing site. Viking 1 returned the first photographs taken from the Martian surface.
The lander studied Martian soil, weather and atmosphere. It carried three biology experiments designed to look for signs of microbial activity, but scientists did not accept the results as definitive evidence of life. Viking also measured surface temperatures, wind and atmospheric pressure.
Viking 1 operated far longer than its planned 90-day mission. Its lander transmitted data until 11 November 1982, and the orbiter continued observations until 1980. Viking 2 landed on Mars in September 1976, making the program the first successful pair of Mars landers.