As NASA celebrates the recent launch of the Perseverance Mars Rover, let’s take a look back at the very first successful NASA spacecraft landing on Mars. It happened during the United States Bicentennial celebration year of 1976. The Viking Project would send a pair of space probes to Mars. Each pair would consist of two parts, an orbiter to circle Mars and a lander to touch down on the surface. These two orbiters and two landers would make the most detailed study of the red planet ever attempted up to that time. The Viking Landers would also be the first spacecraft to have dedicated life detection experiments to search for current signs of living organisms on Mars. Both landers would also be sterilized before launch to prevent contamination of Mars with organisms from Earth.
On August 20, 1975, Viking 1 was launched, followed by Viking 2 on September 9. It would take the spacecraft ten months to reach Mars with Viking 1 entering orbit on June 19, 1976. On July 20 the Viking 1 lander would separate from the orbiter and attempt to land in an area of Mars known as Chryse Planitia or the “Golden Plain”. The landing date also happened to coincide with the seventh anniversary of the Apollo 11 Moon landing that occurred on July 20, 1969. The Viking Landers would land using a combination of parachutes and propulsive rockets. Because of the time delay in sending and receiving signals with Earth, all of the landing sequence would have to be accomplished by a previously designed computer guidance program. This program would tell the lander exactly when to jettison the heat shield, deploy the parachute, and fire the descent rocket engines.
Lander Separation from the Orbiter Viking 1 Lander NASA illustration of Viking Landing Sequence
Fortunately for NASA, everything went as planned and Viking 1 successfully touched down on Mars on July 20, 1976 making July 20 an even more significant date in NASA history. A few weeks later, on August 7, 1976,Viking 2 was also able to make a successful landing in the Utopia Planitia region of Mars. NASA now had four operational probes to study Mars with. Two orbiters above the planet and two landers on the surface. Because the landers were designed to be stationary, they would remain in the spot where they initially touched down for the entire mission. It would not be until July 1997 that a wheeled rover, Sojourner, would be able to explore Mars.
Besides photographing the landing area and collecting other science data on the Martian surface, the two Viking Landers conducted three biology experiments designed to look for possible signs of life. These experiments discovered unexpected and unusual 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 mission biologists, Mars is self-sterilizing. They believe the combination of solar ultraviolet radiation that saturates the surface, the extreme dryness of the soil and the oxidizing nature of the soil chemistry prevent the formation of living organisms in the Martian soil. The question of life on Mars at some time in the distant past remains open.
The two landers were nuclear powered, using radioisotope thermoelectric generators that turn heat energy into electrical energy. Because of this, the landers were very long lived making long term observations possible. Viking Lander 1 made its final transmission to Earth on November 11, 1982 and the last data from Viking Lander 2 was received on April 11, 1980. The Viking Project was a spectacular success for NASA. Both the orbiters and landers revolutionized our understanding of the Martian environment. As the Perseverance Rover begins its journey to Mars, it is important to remember that the Vikings cleared the way by proving that vehicles could land safely on Mars 44 years ago.