Viking Landers

NASA's Viking Project found a place in history when it became the first U.S. mission to land a spacecraft safely on the surface of Mars and return images of the surface. Two identical spacecraft, each consisting of a lander and an orbiter, were built. Each orbiter-lander pair flew together and entered Mars orbit; the lander then separated and descended to the planet's surface.

Spacecraft connection to the Museum

The proof test article of the Viking Mars Lander is on display in the Boeing Milestones of Flight Hall exhibition at the National Air and Space Museum in Washington, DC. More details about the spacecraft are located on its label which is on the main floor.

Additional spacecraft information

When did Viking 1 & 2 launch from Earth and land on Mars?

Launch: Viking 1 launched on August 20, 1975, and Viking 2 on September 9, 1975 from Kennedy Space Center, Florida.

Mars Orbit: Viking 1 reached Mars orbit June 19, 1976; Viking 2 began orbiting Mars August 7, 1976.

Mars Landing: Viking 1 Lander July 20, 1976, landing site Chryse Planitia ("Golden Plain"). Viking 2 Lander September 3, 1976, landing site Utopia Planitia, Mars.

Mission Status: Inactive 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.

What were the mission goals for the Viking Landers?

Obtain high resolution images of the Martian surface
Characterize the structure and composition of the Martian atmosphere and surface
Search for evidence of life

What were some of the findings from the Viking Lander missions?

The Martian surface is a type of iron-rich clay that contains a highly oxidizing substance that releases oxygen when it is wetted.
The surface contains no organic molecules that were detectable at the parts-per-billion level -- less, in fact, than soil samples returned from the Moon by Apollo astronauts.
Nitrogen, never before detected, is a significant component of the Martian atmosphere, and enrichment of the heavier isotopes of nitrogen and argon relative to the lighter isotopes implies that atmospheric density was much greater than in the distant past.
Changes in the Martian surface occur extremely slowly, at least at the Viking landing sites. Only a few small changes took place during the mission lifetime.
The greatest concentration of water vapor in the atmosphere is near the edge of the north polar cap in midsummer. From summer to fall, peak concentration moves toward the equator, with a 30 percent decrease in peak abundance. In southern summer, the planet is dry, probably also an effect of the dust storms.
The density of both of Mars’ satellites is low -- about two grams per cubic centimeter -- implying that they originated as asteroids captured by Mars’ gravity. The surface of Phobos is marked with two families of parallel striations, probably fractures caused by a large impact that may nearly have broken Phobos apart.
Measurements of the round-trip time for radio signals between Earth and the Viking spacecraft, made while Mars was beyond the Sun (near the solar conjunctions), have determined delay of the signals caused by the Sun's gravitational field. The result confirms Albert Einstein's prediction to an estimated accuracy of 0.1 percent -- 20 times greater than any other test.
Atmospheric pressure varies by 30 percent during the Martian year because carbon dioxide condenses and sublimes at the polar caps.
The permanent north cap is water ice; the southern cap probably retains some carbon dioxide ice through the summer.
Water vapor is relatively abundant only in the far north during the summer, but subsurface water (permafrost) covers much if not all of the planet.
Northern and southern hemispheres are drastically different climatically, because of the global dust storms that originate in the south in summer.

What were some of the instruments on the Viking Landers and what were their purposes?

Imaging system - view the scene surrounding the lander, the surface sampler and other parts of the lander, the sun, Deimos, and Phobos to provide data for operational purposes and for geological and meteorological investigations
Gas chromatograph mass spectrometer - search for chemical compounds in the upper surface layer of Mars and measured atmospheric composition near the surface
Seismometer - determine the level of seismic activity on Mars and its internal structure
X-ray fluorescence spectrometer - detect X rays emitted from samples of Martian surface materials irradiated by X rays from radioisotope sources (iron-55 and cadmium-109) -yielded surface composition data
Biological laboratory - search for the presence of Martian organisms by looking for metabolic products
Weather instrument package - analyze the meteorological environment near the planetary surface and obtained information about motion systems of various scales. The atmospheric parameters determined were pressure, temperature, wind speed, and wind direction
Remote sampler arm - a collector head, temperature sensor, and magnet on the end

What was the primary power source for the Viking Landers?

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.

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