Viking 1

By Marty McDowell/NASA

On August 20, 1975, the United States launched Viking 1. First successful soft landing and pictures from the surface of Mars. In fact, it took an interesting and controversial photo that sparked nearly two decades of debate about extraterrestrial life.

The Vikings were the first robotic spacecraft to land on Mars. Their mission was to determine whether life had ever existed in any biological form on the red planet. The first pair of orbiters and landers, Viking 1, was launched on August 20, 1975, followed on September 9 of that year by the second set, dubbed Viking 2. The initial job of both orbiters was to find suitable landing sites for the landers. Later, the orbiters recorded images of the entire surface of Mars, providing informative pictures of volcanoes, lava plains, immense canyons, cratered areas, and valleys. The Viking landers transmitted images of the surface, took samples and analyzed them for composition and signs of life, studied atmospheric composition and meteorology, and deployed seismometers.

NASA The Viking 1 Lander sampling arm created a number of deep trenches as part of the surface composition and biology experiments on Mars. The digging tool on the sampling arm (at lower center) could scoop up samples of material and deposit them into the appropriate experiment. Some holes were dug deeper to study soil which was not affected by solar radiation and weathering. Image courtesy of NASA.

Each spacecraft consisted of an orbiter and a lander. After orbiting Mars and returning images used for landing site selection, the orbiter and lander detached and the lander entered the martian atmosphere and soft-landed at the selected site. The orbiters continued imaging and other scientific operations from orbit while the landers deployed instruments on the surface. The fully fueled orbiter-lander pair had a mass of 3530 kg. After separation and landing, the lander had a mass of about 600 kg and the orbiter 900 kg. The lander was encased in a bioshield at launch to prevent contamination by terrestrial organisms. The total cost of the Viking project was roughly one billion dollars.

The Viking mission was planned to continue for 90 days after landing. Each orbiter and lander operated far beyond its design lifetime. Viking Orbiter 1 functioned until July 25, 1978, while Viking Orbiter 2 continued for four years and 1,489 orbits of Mars, concluding its mission August 7, 1980. Because of the variations in available sunlight, both landers were powered by radioisotope thermoelectric generators -- devices that create electricity from heat given off by the natural decay of plutonium. That power source allowed long-term science investigations that otherwise would not have been possible. The last data from Viking Lander 2 arrived at Earth on April 11, 1980. Viking Lander 1 made its final transmission to Earth November 11, 1982.

Source: NASA.

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Space References (Videos):
Cosmos. PBS, 2000.
Stephen Hawking's Universe. PBS, 1997.
Hyperspace. BBC, 2002.
Life Beyond Earth PBS, 1999.
The Planets. BBC, 1999.
Understanding The Universe. A&E, 1996.