Viking Project

Occurred 46 years ago

Type

Orbiter, Lander

Launch

1975

Target

Mars

Status

Successful

NASA's Viking Project found a place in history in July 1976 when Viking 1 became the first U.S. mission to land a spacecraft safely on Mars and return images of the surface. The project consisted of two identical spacecraft, Viking 1 and Viking 2, each comprised of a lander and an orbiter. Each orbiter-lander pair flew together and entered Mars orbit; the landers then separated and descended to the planet's surface. The Viking 1 lander touched down on the western slope of Chryse Planitia, while the Viking 2 lander settled down at Utopia Planitia. The orbiters continued circling Mars for years past their expected three-month lifespans.

Spacecraft
Launch Date
Purpose
Result
Aug 20, 1975
Mars Orbit & Landing
Successful
Sep 9, 1975
Mars Orbit & Landing
Successful

Besides taking photographs and collecting other science data on the Martian surface, the two landers conducted three biology experiments designed to look for possible signs of life. These experiments discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in soil near the landing sites. According to scientists, Mars is self-sterilizing. They believe the combination of solar ultraviolet radiation that saturates the Martian surface, the extreme dryness of the soil, and the oxidizing nature of the soil chemistry prevent the formation of living organisms there.

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 continued for four years and 1,489 orbits of Mars, concluding its mission August 7, 1980, while Viking Orbiter 2 functioned until July 25, 1978. 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. Viking Lander 1 made its final transmission to Earth November 11, 1982. The last data from Viking Lander 2 arrived at Earth on April 11, 1980.

Two vintage illustrated diagrams of the Viking orbiters and landers. The drawings are labeled with the location of key instruments on the spacecraft.
A diagram of the twin Viking orbiters and landers.
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