In the middle to late 1970s, the United States embarked on a bold exploration of the outer Solar System. It began with the Viking probes, two identical spacecraft sent to Mars in the middle 1970s.
Each consisted of an orbiter and a lander. The lander was designed to photograph the surface, collect and analyze soil samples, and make meteorological observations.
The orbiter's duty was to image and map the planet's surface in detail. By the summer of 1980, the two
Viking landers had sent back
4,200 photos of the surface and three million weather reports. The images showed a desolate rock and sand-dune terrain stretching to the horizon and a dusty pink sky. Viking 1 measured light winds, with gusts of up to
30 miles per hour (50 km/h).
From afternoon to night, temperatures fell from
—20 to —120 degrees Fahrenheit (-30° to-85° C).
Each lander outlived its expected 90-day life span,
Viking 2's functioning until
April 1980, and Viking 1's operating until late November
1982. The orbiters, meanwhile, sent back more than 52,000 photographs.