"This week NASA hosted the Viking Mars Landers 40th anniversary symposium. In 1976 Viking 1 and 2 were the first landers to successfully land on Mars."
"NASA's Viking 1 and 2 missions to Mars, each consisting of an orbiter and a lander, became the first space probes to obtain high resolution images of the Martian surface; characterize the structure and composition of the atmosphere and surface; and conduct on-the-spot biological tests for life on another planet."
"Viking provided the first measurements of the atmosphere and surface of Mars. These measurements are still being analyzed and interpreted. The data suggested early Mars was very different from the present day planet. Viking performed the first successful entry, descent and landing on Mars. Derivations of a Viking-style thermal protection system and parachute have been used on many U.S. Mars lander missions since."