Viking 1 — to the surface of Mars
Launched on 20 August 1975, Viking 1 landed on Mars the following July and sent pictures and data for more than six years. It was the first lander to work on the Martian surface for a long time, and the first to test Martian soil for life.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On 20 August 1975 Viking 1 left Cape Canaveral. It was really two spacecraft joined together: an orbiter to circle Mars and a lander to set down on it. After ten months in space it entered orbit around Mars on 19 June 1976. It did not land right away, though. The team first wanted the orbiter to take close-up pictures of the possible landing sites.
The landing had been planned for 4 July 1976, the 200th birthday of the United States. But the orbiter's pictures showed that the first site was too rough to be safe. So the team searched for a new site, and the landing slipped by sixteen days. Viking 1 came down on the plain called Chryse Planitia on 20 July. By chance, it was exactly seven years after Apollo 11 had landed on the Moon.
The lander's first picture showed one of its own footpads resting on pebbly ground. When the colour pictures arrived, people learned that the Martian sky is not blue but a pale, pinkish tan. The colour comes from fine red dust floating in the air and scattering sunlight. These pictures shaped how people imagined Mars for many years afterwards.
The lander was built to work for 90 days, but it kept going for more than six years. In November 1982 a faulty command sent from Earth accidentally overwrote the software that pointed its antenna, and contact was lost. The orbit view reproduces the ten-month journey from Earth to orbit around Mars.
Mission goals
Viking was the first to show that a spacecraft could land on Mars and keep working there for a long time. The Soviet Mars 3 had reached the surface in 1971, but it fell silent after sending signals for only about 20 seconds. The two Viking landers, by contrast, recorded Martian temperature, air pressure and wind season after season for years. For the first time, the weather on Mars was watched for more than a full Martian year.
Viking's best-known task was to look for signs of life in the soil. In one experiment, adding nutrients to the soil released gas, which looked as though something might be alive. But another experiment found no organic molecules, the building blocks of living things. So most scientists concluded that the gas came from chemical reactions in the soil, not from life. Even so, the question has never been completely settled.
These puzzling results changed the direction of Mars exploration. Instead of looking straight for life, NASA decided to look first for signs of water and for places where life could once have lived. Pathfinder, Spirit, Curiosity and Perseverance followed that plan one after another.
Mission chronology and background
The air on Mars is very thin, about 1 percent as dense as Earth's. A parachute alone could not slow the lander enough. So the Viking lander opened its parachute about 6 km up and then fired braking rockets from about 1.5 km, gently descending the last stretch. It touched down at about 2.4 metres per second, roughly the speed of a brisk walk.
If microbes from Earth reached Mars, the results of the life experiments could not be trusted. So before launch each Viking lander, sealed inside a protective shell, was heated to 111 °C for 40 hours to sterilise it. Efforts like this to avoid contaminating other worlds with Earth life are called planetary protection.
Its twin, Viking 2, landed on Utopia Planitia on 3 September 1976 and worked until its batteries failed in April 1980. No spacecraft landed on Mars again for 21 years, until Pathfinder bounced down on airbags in 1997. In 2008 the Phoenix lander found chemicals called perchlorates in Martian soil. Scientists then suggested that these may have destroyed organic molecules during Viking's analysis.
Where to see it — sky and simulator
The Viking 1 lander still stands on Chryse Planitia, at about 22.7° N, 48° W. No telescope on Earth can see it, but the Mars Reconnaissance Orbiter, circling Mars since 2006, has photographed it from above. In those pictures the lander appears as a bright spot only a few pixels across.
Mars itself is visible to the naked eye as a reddish star. Select it in the sky view to see its height, direction and rising time from where you are. Move the orbit view to 20 July 1976 and it reproduces where Earth and Mars were around the Sun on the day of the landing.
See this for yourself — replay the moment in the orbit view
FAQ
Why did it land on 20 July?
It was meant to land on 4 July, but the first site proved too rough, and finding a new one took sixteen days. The new date happened to be the seventh anniversary of Apollo 11's Moon landing.
Did it find life?
Most scientists concluded that it did not. Gas was released, but no organic molecules were found, so the gas is thought to come from chemistry in the soil. The debate is not entirely closed.
How long did it work?
It was built for 90 days but worked for more than six years, until November 1982.
Why is the Martian sky pinkish?
Because fine red dust floating in the air scatters sunlight. Viking's colour pictures were the first to show it clearly.
Related
- Mariner 4 — first close-ups of Mars
- Curiosity launch
- Perseverance launch
- Mars — object index
- Perseverance — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.