An orbiter and a lander
Viking 1 combined an orbiter and a lander. Launched in 1975, it reached Mars orbit in 1976. The orbiter photographed terrain for landing-site assessment, while the lander carried cameras, environmental instruments and soil experiments.
Orbital images revealed hazards at the initially selected site. The team continued its search and selected a location in western Chryse Planitia.
The descent of July 20, 1976
On July 20 the lander separated and entered the Martian atmosphere. Its aeroshell used atmospheric drag to slow the descent while thermal protection shielded the equipment. A parachute and terminal engines provided further deceleration. It touched down at about 11:53 UT and began transmitting pictures.
The first images showed rocks and soil beside the craft. Later scans covered a wider view, supplying detailed pictures of the surroundings in Chryse Planitia.
Sampling soil and recording weather
An arm delivered soil to instruments for chemical analysis and biology experiments. Sensors recorded temperature, pressure and wind through daily and seasonal changes. Images also showed particles, rocks and soil behaviour during sampling.
The preliminary 1976 study examined physical surface properties revealed by the landing feet and sampling operations. The experiments did not establish definitive evidence of life, and soil chemistry remained a subject of research.
Long-term work on another planet
Viking 1 established a long-running surface station with cameras, weather sensors and a laboratory. Orbital imagery could be compared with ground measurements. Operations extended far beyond the initially planned months and recorded multiple seasons.
The data supported work on local geology, atmosphere and soil, and preparation for later landing and surface operations. Mars could be examined both from orbit and through details measured on the ground.