 In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds.Later much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission.Venus and Mars are the two planets outside of Earth, humans have conducted surface missions on with unmanned robotic spacecraft.