The Viking Mars Mission

In October 1957, the Soviet Union launched the first satellite, Sputnik. Over the next 20 years, the Space Race saw the USSR and the USA compete in a series of space spectaculars as each tried to show off their economic and technological superiority. But during this time, there was also some excellent science being done, which got far fewer headlines. One of the most successful of these was the Viking program to study the planet Mars.

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Viking Lander, California Science Center

Sputnik was a simple hollow metal sphere with a radio transmitter inside. The first American satellite, Explorer I, was not much better, though it did carry a Geiger counter to measure radiation levels in space. The Russian rockets were much more powerful than the American, though, and their bigger payload capacity meant that Soviet satellites soon became larger and more sophisticated. Sputnik 2, launched in November 1957, carried the first living organism into space–a dog named Laika. In May 1958, Sputnik 3, weighing almost a ton and a half, carried twelve instruments to study the Earth’s atmosphere. After the success of Sputnik 3, the Soviets were ready to attempt to send unmanned probes to the rest of the solar system, including Mars.

But all the early attempts failed. From 1960 to 1971, the Soviets launched a total of 9 unmanned probes intended to reach Mars. Many of them blew up on launch; others lost radio contact in space on the way there. In 1964, the US joined the race, launching its Mariner probes, which were intended to fly close to the planet and photograph its surface. Mariner 3, in 1964, failed, but Mariner 4, in July 1965, passed Mars at a distance of about 6,000 miles, sent back the first closeup photos of the surface, and detected a thin CO2 atmosphere and a very weak magnetic field. Two more fly-by missions, Mariner 6 and Mariner 7, followed in 1969.

In 1971, the first attempt was made, by the Soviet Union, to land a probe on the Martian surface. Called “Mars 2”, it reached Mars orbit in November 1971 and dropped its lander, which malfunctioned on the way down and crashed on the surface, returning no data. It was, however, the first man-made object to impact the surface of Mars. A week later, the Mars 3 probe successfully landed and transmitted measurements of temperature and atmospheric conditions. During this time, the American Mariner 9 entered orbit around Mars and sent back high-resolution photos of the Martian surface.

After the success of the Moon landing in 1969, though, NASA had made some ambitious plans for space exploration. One of these was a program for a manned space station called “Skylab”. Another was the “Voyager Mars” program. In the Voyager Mars project, a modified Saturn 1B rocket would launch a modified Apollo Command Module as an unmanned probe that would enter Mars orbit and then land on the surface. Later, the plan was changed–now a Saturn V would launch a modified Mariner probe into orbit around Mars, which would then drop a modified Surveyor probe (used for unmanned Moon landings) to the Martian surface. Two Voyager Mars landings were planned–they were intended to serve as reconnaissance missions in support of a manned Mars landing sometime in the 1980’s. The total cost would be about $2 billion.

Once the US reached the Moon, however, the political interest in space exploration plummeted. Several planned Apollo landings were cut, and the entire Voyager Mars program was cancelled.

But NASA kept the idea alive, drawing up plans for a simpler, cheaper Mars program called “Viking”. The Viking project would use a Titan III rocket with an added Centaur upper stage to launch a simplified version of the Voyager Mars orbiter/lander. Although it was greatly scaled down from its predecessor, the Viking mission was still the most expensive NASA Mars program proposed to that time (the total budget was $1 billion, or $3.4 billion in today’s dollars), and NASA had to fight hard to win funding for two missions, Viking 1 and Viking 2, which would be flown within just a few days of each other.

Each Viking craft consisted of two parts: the orbiter, and the lander. The orbiter was a modified version of the Mariners that had already been successfully sent to Mars. They were designed to carry the lander to Mars, release it, then stay in orbit to conduct photography and instrument study of the Martian atmosphere and surface. Not counting fuel, the orbiter weighed around 2,000 pounds. Power came from internal nickel-cadmium batteries and four solar panels. The lander was a modified Surveyor lunar probe, which carried a battery of scientific instruments including cameras, wind sensors, seismometers, and a series of instruments designed to look for possible life in the Martian soil. The Viking lander weighed around 1300 pounds.

The two missions were ready in 1975. Viking 1 was launched on August 20, 1975, and Viking 2 followed on September 2. It took almost a year for the two probes to reach Mars, and Viking 1 finally entered orbit around the Red Planet on June 19, 1976, with Viking 2 following on August 7.

Touchdown on the surface of Mars for Viking 1 was scheduled for July 4, 1976–the nation’s Bicentennial. But as the probe orbited around the planet, high-resolution photography of the surface showed that the planned landing site, at Chryse, was far rockier and rougher than had been thought, and it was decided to delay the landing to find a better site. On July 12, the NASA team selected a new landing site at Chryse Planitia, about 365 miles away from the original location. The new landing date was set for July 20, the anniversary of the Apollo Moon landing. Viking 2 reached Mars orbit in August, and landed a few hundred miles away at Utopia Planitia.

Although the Viking missions had only been planned to last for 90 days, they both continued to function for several years. The Viking 2 Orbiter returned data and photos until July 1978, while the Viking 1 Orbiter lasted until August 1980. The Viking 2 Lander stopped sending data in April 1980, and the Viking 1 Lander lasted until November 1982. The Orbiters photographed about 97% of the planet’s surface, revealing features that looked like canyons, volcanoes, and ancient riverbeds. The Landers revealed that the surface soil was an iron-rich powder with several types of volcanic rock, that the atmosphere was very thin and consisted mostly of carbon dioxide, and that the surface temperature at the landing sites varied from day to night, from 1 degree F to minus 178 degrees F.

But the most eagerly anticipated experiments were those that were designed to find potential life on Mars. The Viking Landers each carried three instruments to look for life. The first of these was the Labelled Release Experiment, which took a sample of Mars soil, added a small amount of nutrient solution containing radioactive Carbon-14, then monitored the sample to search for signs of radioactive C-14 being released as a metabolic waste product. The second package was the Carbon Assimilation Experiment, which introduced radioactive Carbon-14 to soil and air samples and then looked for concentrations of C-14 that would indicate the presence of microbes that had ingested it. And the third test was the Gas Exchange Experiment, which added a nutrient solution to a soil sample and then monitored for any buildup of gases which would indicate the release of metabolic waste products.

At first, the results of the Viking experiments were staggering: the Gas Exchange Experiment showed a significant release of oxygen, and the Carbon Assimilation Experiment showed a marked concentration of C-14. It was exactly what the scientists had expected to see if there was microbial life present in the Martian soil.

But, alas, those hopes were quickly dashed. The oxygen release happened too quickly to be attributed to metabolism, and the C-14 concentrations quickly dropped off rather than increasing as they would if Martian microbes were multiplying in the soil. Further investigation concluded that both results had been the product of unusual chemical reactions in the Martian soil, and not the result of biological activity. Mars, at least currently, was lifeless.

But despite that disappointment, the Viking mission was a tremendous success. Data from Viking 1 and Viking 2 provided nearly all of our knowledge about Mars throughout the 70’s and 80’s, and the photos of surface features from the orbiters gave the first indications that Mars had liquid water–and possibly life–in its geological past.

Today, the engineering model of the Viking Landers, originally built for testing by Lockheed-Martin for NASA, is on display at the California Science Center in Los Angeles.

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2 thoughts on “The Viking Mars Mission”

  1. I was still a kid at the time, but I well remember my excitement when photos of the Martian surface were published in magazines here. It’s as Carl Sagan once remarked: Mars is a place. The photos reminded me pretty much of the Karoo here in South Africa. 🙂

    I think it’s pretty unlikely that there is any life on Mars at present. But who knows what fossils may be dug up there in the future…

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