The first spacecraft on Mars safely. The one that started it all. The Viking mission had two trials, both consisting of a lander-orbiter pair that would operate in tandem to give Mission Control as much data as possible. Both missions were very successful, landing in 1976 on the Plains of Gold for Viking 1 and Utopia Planitia for Viking 2. They contained several instruments to measure biological signs, chromatography units and mass spectrometers, seismometers, soil analysis systems, and weather instruments.
We consider some of the greatest data collected by the Vikings to be their full color images, transmitting some of the most detailed images that had ever been seen of a planet besides our own. However, data about the planet sent back revealed the first signs of organochemical activity on the surface of the planet, but it was concluded that Mars could not sustain life in its current state due to the intense solar radiation that penetrates the Martian surface quite easily as well as the highly oxidizing, rocky soil. Other early signs of a metal core on Mars and weather data were very important to our knowledge of how it may have changed over time.
Perhaps the greatest revolution in the Viking 1 & 2 tandems was their power system; both used thermoelectric generators powered by radioactive plutonium that extended their lives far beyond the 90 days initially expected; the heat generated by the decomposition of the plutonium resulted in both orbiters lasting for multiples of that 90 days. Viking 1’s orbiter functioned for 4 years until August 7, 1980 and 2’s finally failed on July 25, 1978. The landers lasted even longer, with radio silence only beginning on November 11, 1982 and April 11, 1980, respectively.