NASA's Viking 1 Mars orbiter ends mission after 4 years

On Aug. 7, 1980, NASA's Viking 1 orbiter shut down after four years circling Mars, far exceeding its planned 90-day mission. Launched in 1975, Viking 1 was the first spacecraft to land on Mars, and its orbiter helped select the landing site. The lander continued operating until 1983, when it lost contact with NASA.