Viking Lander 2 landed at Utopia Planitia on Mars on 3 September 1976.  Besides a lander for surface investigations there was also a paired orbiter to study Mars from orbit.  The Viking 1 & 2 orbiters and landers launched from Cape Canaveral in August and September 1975 and spent about a year cruising to Mars before becoming the first American mission to land safely on the surface of the red planet.  While the orbiters were solar powered, the landers were powered by small radioisotope thermoelectric generators (RTG) converting heat from decaying plutonium-236 into 70 watts of electrical power.  The generators provided a long-lived source of electricity and heat on Mars, where sunlight is half as strong as on Earth and temperatures during the Martian night can drop as low as -120 C (-184 F).

Viking Lander previously on display at the Kennedy Space Center Visitor Complex.

Viking Lander on display at the National Air and Space Museum in Washington, D.C.  Note the arm with a scoop on the end for collecting and delivering soil samples to the onboard science instruments.