America's bicentennial Mars landers were spectacular:
Viking Probes From Earth Landed on Mars in 1976
The story of Viking 1 The story of Viking 2
Planetary exploration moved into a new era with the landing of science instrument packages on the Red Planet.
Viking 2 photo of the red rocky Martian field
click NASA image to enlarge
Viking 1 image collection »
Viking 2 image collection »
In particular, America's bicentennial attempts to land on the planet were highly successful.
Viking 1 and Viking 2 carried the American flag across millions of miles of interplanetary space to photograph Mars and its moons Phobos and Deimos, and then land on the Red Planet in 1976.
The Vikings were by far the most scientifically-profitable Martian operations until the late 1990s.
Landing on faraway places. What's so great about planetary landers?
- They are able to make actual contact with the surface and the atmosphere at the surface.
- They can make first hand measurements of soil and weather.
- They can dig beneath the surface to see what's down there.
- They can send back close-up photos of the region around the lander.
- If they have mobility, landers can explore larger areas of the planet's surface.
- Over time, they can report seasonal and long-term changes in Martian surface features.
The Mars Global Surveyor spacecraft orbiting the Red Planet has photographed the Viking 2 lander down on the surface »»
Viking 1
America's Viking 1 was launched September 9, 1975, and went into orbit around Mars on June 19, 1976. It carried two television cameras which made 26,000 photos of Mars and the Martian moons Phobos and Deimos.
NASA COLLECTION OF VIKING 1 IMAGES
The lander parachuted to the Martian surface on July 20, 1976, where it worked for 6.5 years until Nov. 13, 1982.
It housed a weather station, seismometer and soil analyzer. The seismometer failed. The television camera showed a red rocky surface, a dusty pink sky, sand dunes and no large life forms. The soil was found to be mostly silicon and iron. Surface temperatures ranged from +20 to -120 degrees. The winds were recorded at 30 mph.
The first-ever detailed measurements of the surface and atmospheric conditions of the Red Planet began that July 20 as the Viking 1 lander touched down on a rocky Martian desert called Plains of Gold (Chryse Planitia). That unmanned landing on Mars came seven years to the day after the first Apollo manned landing on the Moon.
During and after its descent, Viking 1 measured the composition and structure of the Martian atmosphere. It found:The atmospheric pressure on the Plains of Gold -- which is a basin some 1.2 miles (2 kilometers) below an imaginary reference "sea level" on Mars -- was about 7.5 millibars. By comparison, sea-level pressure on Earth is about 1,000 millibars.
- 95 percent carbon dioxide, 2 to 3 percent nitrogen, 1 to 2 percent argon, and tiny traces of oxygen and water vapor.
- Ozone to screen out ultraviolet light was almost nonexistent.
- Water vapor also was almost totally absent near the Winter polar cap, but in the Summer hemisphere, where both Viking 1 and Viking 2 landed, water vapor existed in amounts about 5/100 that found in the driest parts of Earth.
Detailed anaylsis of the atmosphere turned up evidence that, in the past, atmospheric pressure was probably higher, supporting conclusions derived from observation of dry river channels.
Temperatures at the Viking landing sites depended on the time of day:Winds were a gentle 6 to 8 mph with occasional gusts of 30 to 40 mph.
- After dark the Viking 1 lander chilled to -123 deg F (187 K), but warmed during the day to -20 deg F (244 K).
- Soil temperatures were higher than those in the thin Martian atmosphere near ground and rose above freezing during the Summer months.
- By contrast, polar temperatures during Winter were -197 deg F (146 K). The more northerly Viking 2 recorded such low temperatures during Winter months.
The Viking 1 lander surveyed the terrain:Scientists weres urprised to see a light pinkish-grey Martian sky, not the dark blue they had expected. The coloring may have come from fine dust particles suspended in the atmosphere.
- It was surrounded by a dusty, red plain littered with both dark and reddish rocks.
- One boulder measured 3 feet by 10 feet (1 by 3 meters).
- Drifting soil had piled up near the rocks and formed a dune field not far from the lander.
Viking 2
America's Viking 2 was launched August 20, 1975, and went into orbit around Mars on August 7, 1976. It carried two television cameras which made 26,000 photos of Mars and the Martian moons Phobos and Deimos.
NASA COLLECTION OF VIKING 1 IMAGES
The lander parachuted to the Martian surface on September 3, 1976, where it worked for 3.5 years until April 2, 1980.
It housed a weather station, seismometer and soil analyzer. The lander found wind, minor marsquakes, a red rocky surface, a dusty pink sky, sand dunes and no large life forms. The soil was mostly silicon and iron. Surface temperatures ranged from +20 to -120 degrees. The winds were recorded at 30 mph.
The lander touched down that September 3 in Utopia, a Martian region much farther north than the Plains of Gold. Viking 2 was at latitude 48 degrees north compared to the 22.5 degrees north latitude of Viking 1.
The spot where Viking 2 planted itself was more of a rock-strewn plain and less dusty than the Viking 1 site some 4,660 miles (7,500 kilometers) away.
Rocks were abundant at Utopia. Most showed the same reddish stain from iron oxide seen at the Viking 1 site.
The soil of Mars where both Vikings landed was like basaltic lava, but heavily enriched in iron and depleted in aluminum. The iron was in a highly oxidized state. Results of chemical and biological analysis on the spot suggested the presence of superoxides, peroxides, and ozonides. Those unusual compounds contribute to the color of the Martian deserts. They probably were formed by the small amount of water vapor and the ultraviolet light that reaches the surface.
At the time of landing, Viking 2 found nearly three times as much water vapor in the air over Utopia as Viking 1 had observed over the Plains of Gold.
Mars seemed less active than Earth because very little seismic noise was recorded by seismometers.
