Viking 1
First successful Mars lander, operated over six years.
Viking 1 was the first of two spacecraft—each made up of an orbiter and a lander—launched under NASA's Viking program. Its lander made history on July 20, 1976, by becoming the first to successfully touch down on Mars. It remained active on the Martian surface for 2,307 days (more than six and a quarter years, or 2,245 Martian solar days), holding the record for the longest-running extraterrestrial surface mission until the Opportunity rover broke it on May 19, 2010.
The mission began with a Titan/Centaur launch on August 20, 1975, followed by an 11-month journey to Mars. The orbiter started sending back global images of the planet about five days before entering orbit. It entered Mars orbit on June 19, 1976, and was adjusted to a certification orbit of 1,513 by 33,000 kilometers with a 24.66-hour period on June 21. The original landing date was July 4, 1976—the U.S. Bicentennial—but images of the primary site showed it was too rugged for a safe landing. The landing was postponed until a safer location was found, and it finally occurred on July 20, the seventh anniversary of the Apollo 11 Moon landing. The lander separated from the orbiter at 08:51 UTC and touched down in Chryse Planitia at 11:53:06 UTC. It was the United States' first attempt at landing on Mars.
The orbiter carried two vidicon cameras for imaging, an infrared spectrometer to map water vapor, and infrared radiometers for thermal mapping. Its primary mission ended at the start of solar conjunction on November 5, 1976, and the extended mission began on December 14, 1976, after conjunction. In February 1977, the orbiter made close approaches to Phobos. Periapsis was lowered to 300 kilometers on March 11, 1977, and minor orbit adjustments were made over time, mainly to change the walk rate—how quickly the areocentric longitude shifted per orbit. On July 20, 1979, periapsis was raised to 357 kilometers. By August 7, 1980, the orbiter was low on attitude control gas, so its orbit was raised from 357 by 33,943 kilometers to 320 by 56,000 kilometers to avoid crashing into Mars and potentially contaminating it until 2019. Operations ended on August 17, 1980, after 1,485 orbits. A 2009 analysis concluded that, while an impact with Mars could not be ruled out, the orbiter was most likely still in orbit. It sent back more than 57,000 images.
The lander and its aeroshell separated from the orbiter at
- launch_date
- August 20, 1975
- landing_date
- July 20, 1976
- mission_end
- November 11, 1982
- field
- Space exploration
- nationality
- United States
- known_for
- First successful Mars lander; longest surface mission until 2010
Lore & Background
Viking 1 launched on a Titan/Centaur vehicle on August 20, 1975, and after an 11-month cruise, its orbiter began returning global images of Mars. The orbiter was inserted into Mars orbit on June 19, 1976, and the landing was initially planned for July 4, 1976, but was delayed due to rough terrain at the primary site. The lander separated from the orbiter on July 20, 1976, at 08:51 UTC and touched down at Chryse Planitia at 11:53:06 UTC, the seventh anniversary of the Apollo 11 Moon landing.
Reader's Guide
Viking 1's significance lies in its pioneering role as the first successful Mars lander, providing the first surface images and extensive data on Martian soil, atmosphere, and potential for life. Its biology experiments yielded mixed results: the labeled release experiment gave a positive response for life, while other tests were negative, leading to ongoing debate. The mission also demonstrated long-duration surface operations, lasting over six years until a faulty command ended contact. Its orbiter returned more than 57,000 images and operated until August 17, 1980. The lander was later named the Thomas Mutch Memorial Station.
Did You Know?
- The lander touched down on July 20, 1976, the seventh anniversary of the Apollo 11 Moon landing.
- Viking 1 operated on Mars for 2,307 days, the longest extraterrestrial surface mission until broken by Opportunity in 2010.
- The lander's labeled release experiment gave a positive result for life, but most scientists attribute it to inorganic chemical reactions.
- The orbiter's orbit was raised in 1980 to prevent impact with Mars until at least 2019.
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