The NASA Viking Mission to Mars was composed of two spacecraft, Viking 1 and Viking 2,
each consisting of an orbiter and a lander. The primary mission objectives were to
obtain high-resolution images of the Martian surface, characterize the structure and
composition of the atmosphere and surface, and search for evidence of life.
Viking 1 was launched on August 20, 1975 and arrived at Mars in June 19, 1976. The
first month of orbit was devoted to imaging the surface to find appropriate landing
sites for the Viking Landers. On July 20, 1976 the Viking 1 Lander separated from
the Orbiter and touched down at Chryse Planitia.
Viking 2 was launched September 9, 1975 and entered Mars orbit on August 7, 1976.
The Lander touched down at Utopia Planitia in 1976. The Orbiters imaged the entire
surface of Mars at a resolution of 150 to 300 meters, and selected areas at 8 meters.
The Viking Landers transmitted images of the surface, took surface samples and analyzed
them for composition and signs of life, studied atmospheric composition and meteorology
and deployed seismometers. The results from the Viking experiments gave us our most
complete view of Mars to date.
The surface material at both landing sites was best characterized as iron-rich clay.
Measured temperatures at the landing sites ranged from 150 to 250 K, with a variation
over a given day of 35 to 50 K. Seasonal dust storms, pressure changes, and transport
of atmospheric gases between the polar caps were observed. The biology experiment
produced no evidence of life at either landing site.