VIKING 1 & 2 (1976)

I RISULTATI DELLA MISSIONE VIKING

Photo Gallery

 

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The lander seen here is the Science Test Lander. It has operational cameras and surface sampler.

The success of Mariner 9 was truly phenomenal. But did life actually exist on Mars? The observations of Mariner 9 did not prove or disprove the possibility. If it did exist, it would have to survive in an atmosphere of carbon dioxide, an atmosphere so thin that it would equal that of the Earth 20 miles (32 km) above the surface. It would have to survive the strong radiation of the sun, particularly ultraviolet radiation. It would have to survive sudden and extreme tem- perature changes ranging from a balmy SO degrees Farenheit (27’C) at noon-day on the equator to a chilling 150 degrees below zero ( – 65’C) at night. It would have to get along with little or no water. No water in liquid form appeared to exist on Mars, despite the appearance of erosion and dry ’river beds.’

 

 

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Orbiter main elements

 

 

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The Orbiter  cameras

 

 

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Lander main elements

 

 

 

 

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Project Scientist Gerald Soffen

during a test on a

Viking lander proptotype

in the California desert

(Gerald Soffen courtesy)

In the midst of all the questions, the Viking program came into being. Nearly ten years of planning and complex designs went into the Viking Project. Then on 20 August and 9 September 1975, the twin spacecraft were launched. They would cross 400 million miles (643,000,000 km) through the empty darkness of space to reach their goal, the ’red’ planet, Mars. It would be almost a year before they reached their destination. Each craft consisted of two parts: an orbiting satellite which would photograph the Martian surface and a lander which would separate from the satellite and descend to the planet’s surface. As it came closer to the chosen landing site, retrorockets would be fired to slow its descent. Parachutes would be deployed, slowing the descent further. Viking I began its orbit around Mars on 19 June 1976. Its task was to select a landing site for the lander. Three Russian probes had previously been des- troyed on impact with the Martian surface. Selecting the site was, therefore, no mean task. Over a billion dollars had gone into the Viking Project and NASA was not anxious to see the Viking lander come to such a fate. Out of cautiousness, the site that seemed most desirable would be smooth and fairly level. The data collected from the orbiter cameras and from the Earth-based radar scans would be conducted from the largest radiotelescope on Earth at Arecibo, Puerto Rico. Several possible sites were rejected as ’too rough’ before the site at Chryse Planitia (Plain of Gold) was chosen.

 

 

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Jet Propulsion Laboratory: the Mission Control Center

 

 

 

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The decision: land at Utopia Planitia

 

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The historic first photograph sent back from Mars, minutes after the successful landing of Lander 1 on July 20, 1976.

 

On 20 July 1976, Viking I landed successfully on Mars. Within an hour of the landing, the first photo of Mars were being radioed back to Earth. Viking scientists were jubilant. Poised on its three metal legs, the Viking lander began to function by activating all of its electronic sensors. It rotated its twin cameras, capable of giving a three dimensional view of the landscape, to focus on the horizon. The mass spectrometer tested the atmosphere to determine its composition. A metal arm rose up to check the weather conditions, temperature, barometric pressure, wind speed and direction. All of this data was relayed to the Viking orbiter, which in turn relayed it back to Earth. In size, the Viking lander was similar to a compact car. Literally all of its equipment, the cameras, the transmitters, sampler ’arm’ and over a dozen test devices and sensors were powered by a single 50 watt generator. This amounts to less power than that used by an average household light bulb. Within the limited confines of the lander were three automated chemical laboratories. These contained tiny ovens, filters, counters for radioactive tracers, a gas chromatograph which would identify che- mical substances and a lamp which would reproduce the weak sunlight found on Mars. All of this was packed into one cubic foot! Along with all of this were 300,000 transistors, 2000 other electronic parts, 1000 wire connections and 37 miniature valves. The miracle is that all of these functioned perfectly despite the great distances traveled, the ordeal of landing and the harsh climate of Mars. (The range of temperatures experienced on that first Martian day went from – 30 to – 86 C. ( – 23 to – 123 degrees Fahrenheit). The Viking far exceed their planned mission life (90 days). Lander 2 ceased transmissions in 1980, while Lander 1 lasted until 1982.

 

 

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A portrait of project members and spare lander, reflected in a mirror, was made at JPL by Lander camera. The left-toright scan took 12 minutes. Scientist at right were still posing long aftercolleagues had gone.

 

 

 

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The landers cameras

 

 

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If anything moves, landers cameras can spot it. Recording images slowly one vertical scan at a time, a camera can endlessly repeat a scan, building a band of light and dark. Any motion would break the pattern.

 

 

 

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The collector sempler of the landers

 

Most of the tests were aimed at discovering life or some evidence that life had existed on Mars. One cell contained a mixture that scientists dubbed ’chicken soup.’ Nutrient rich, it was supposed to encourage growth, reproduction or metabolization of whatever life form might exist on the planet. This was all accomplished with extremely complicated machinery.

 

 

 

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The trouble-some pin that prevented the extension of the boom during  the initial sequence of the extension.

 

 

 

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The Viking biology instruments

A delicate-looking steel arm with a shovel at its end would reach out to a distance of ten feet. At that point, it would turn at the wrist and drop to the ground. When the shovel made contact with the ground, it would click open. It would then push firmly into the soil, scooping up a sample and click closed. Then it would swivel its wrist again and retract the long arm. The precious load of soil was carried back to the spindly little craft. Over a cylinder covered by a wire screen, the arm paused. The shovel lid began vibrating violently. Dust and rock particles sifted from holes in the shovel. The earth samples disappeared into the craft. Within the craft, measured samples were carried by a rotating conveyor to several test cells. Each sample would receive a battery of tests, designed specifically to find evidence of life. Even with all this complex machinery, all the careful tests, scientists to this day cannot say with certainty whether there is life on Mars. Some of the experiments such as the ’labeled release’ test produced very strong evidence for the presence of some type of microbe similar to Earth bacteria or algae. In this test,

soil was moistened with the nutrient solution. Then the

 

amount of carbon-dioxide gas was measured as it was discharged from the soil.

 

 

The answer is still a calculated ’maybe.’

The amount of carbon dioxide released in this experiment was quite high; exactly what would be expected from the metabolism of micro- organisms. The results for this test were the same at each of the two Viking lander loca- tions. Each control test, in which the soil was first sterilized by heat, showed no release of any gas. This test alone would seem almost positive proof of living organisms on Mars. But the reactions from other tests were so strange that scientists declined to make any positive statements. One of the other life-detection tests called the Gas-Exchange Experiment produced a sudden and unexplainable burst of oxygen when Martian soil was exposed to moisture. Scientists felt this seemed to be a non living chemical reaction rather than a response produced by living organisms. Perhaps the ’labeled release’ test was also a chemical reaction. The biggest puzzle of all was the results of the GCMS (gas chromatograph mass spectrometer). The object of this experiment was to find organic (carbon- based) chemicals in the Martian soil. Carbons occur naturally, even in the depths of space. Carbon is one of the compounds common to all life. Yet the Martian soil yielded none of these organic chemicals. It was baffling. It is still baffling, although some recent tests done with Antarctic soil show much the same reactions as those done on Martian soil. Antarctica comes close to duplicating the temperatures and lack of moisture on Mars. Is there life on Mars.’

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