Viking 1 and 2
The landers that sniffed the Martian air, and so proved that some meteorites come from Mars.
Key facts
- Agency
- NASA (United States)
- Type of mission
- Orbiters and landers
- Target
- Mars: Chryse Planitia and Utopia Planitia
- Launched
- 20 August and 9 September 1975
- Status
- Completed 1982
Each Viking mission was a pair: an orbiter that mapped Mars from above and a lander that set down on the surface. Viking 1 landed on Chryse Planitia on 20 July 1976 and Viking 2 on Utopia Planitia on 3 September 1976. They sent back the first clear pictures from the Martian surface, tested the soil for signs of life and worked for years, the last lander until 1982.
A fingerprint in the air
Among the landers' most important measurements was the make-up of the thin Martian atmosphere: about 95% carbon dioxide, with nitrogen and argon, and particular ratios of isotopes of noble gases such as argon and xenon. That mixture is unlike Earth's air or any other known gas.
The link to meteorites
In the late 1970s a small group of meteorites, the shergottites, nakhlites and chassignites, looked suspicious. They were young volcanic rocks, a few hundred million to about 1.3 billion years old, far younger than rocks from asteroids, so they had to come from a planet that stayed volcanic for a long time.
In 1983 scientists measured gas trapped in pockets of shock-melted glass inside the Antarctic shergottite Elephant Moraine 79001. Its gases matched the Viking measurements of the Martian air almost exactly. The shock of the impact that launched the rock from Mars had sealed a sample of the atmosphere inside it. This was the proof that Martian meteorites are real, and it is still the strongest test for a meteorite claimed to be from Mars.
Key dates
| Date | What happened |
|---|---|
| 20 August 1975 | Viking 1 launched. |
| 9 September 1975 | Viking 2 launched. |
| 20 July 1976 | Viking 1 landed on Chryse Planitia. |
| 3 September 1976 | Viking 2 landed on Utopia Planitia. |
| November 1982 | Contact with the Viking 1 lander, the last working Viking craft, was lost. |
| 1983 | Gas trapped in the meteorite EETA 79001 was found to match the Viking measurements of the Martian air. |
See where this mission fits among all the others in the mission timeline.
Did you know?
The Viking 1 lander worked on Mars for more than six years.
The Martian meteorites were once called SNC meteorites, after Shergotty, Nakhla and Chassigny.