The NASA Viking Lander 1 successfully reached the surface of Mars in July 20, 1976, due to the testing AEDC conducted on the launch vehicle and the entry vehicle parachute system.
The Titan III/Centaur launch vehicle for the lander was tested in the Propulsion Wind Tunnel in the mid-1960s and the entry vehicle system was tested in PWT and the von Kármán Gas Dynamics Facility from 1969 through 1973.
Viking testing at the Arnold Engineering Development Center, Arnold Air Force Base, Tenn., focused on how the systems would endure the type of atmosphere and environment surrounding Mars.
Viking 1 collected samples and conducted biology experiments on Mars to search for signs of living organisms. The distance for Viking to travel to Mars was 500 million miles, which was a trip that took 11 months.
The lander collected data from Mars for more than six years according to a Viking mission overview by NASA in 2015.
The overview also reported, “The landers [Viking 1 and Viking 2] accumulated 4,500 up-close images of the Martian surface. The accompanying orbiters provided more than 50,000 images, mapping 97 percent of the planet.”
The data is continually analyzed, and the thermal protection system and parachute were used on other Mars lander missions such as the Mars Pathfinder and the Mars Exploration Rovers, Spirit and Opportunity.