Viking program
Two American probes that landed on Mars in 1976.
In 1975, NASA launched two nearly identical spacecraft, Viking 1 and Viking 2, which both reached Mars and set down on its surface in 1976. The project, overseen by the NASA Langley Research Center, had been in development since 1968. Each probe had two sections: an orbiter to photograph the planet from above and a lander to study it from the ground. The orbiters also acted as communication relays for the landers after touchdown. This program grew out of an earlier, more ambitious NASA concept called Voyager Mars, which is unrelated to the later Voyager deep-space missions.
Viking 1 lifted off on August 20, 1975, and Viking 2 followed on September 9, both launched on Titan IIIE rockets with Centaur upper stages. Viking 1 entered Mars orbit on June 19, 1976, and Viking 2 arrived on August 7. After spending over a month in orbit sending back images to help pick landing spots, the orbiters and landers separated. The landers then plunged through the Martian atmosphere and made soft landings at the chosen sites. Viking 1’s lander touched down on July 20, 1976, more than two weeks before Viking 2 reached orbit. Viking 2’s lander soft-landed on September 3. The orbiters kept taking pictures and doing science from orbit while the landers worked on the surface. The program ended in 1982.
The mission cost roughly $1 billion at launch, about $6 billion in 2024 dollars. It was considered a success and provided most of what scientists knew about Mars until the late 1990s and early 2000s.
The science goals were to get high-resolution images of the Martian surface, figure out the structure and makeup of the atmosphere and surface, and look for signs of life.
The orbiters’ main jobs were to carry the landers to Mars, scout and confirm landing sites, relay communications for the landers, and do their own research. Each orbiter, based on the Mariner 9 design, was an octagon about 2.5 meters across. The fully fueled orbiter-lander combo weighed 3,527 kilograms. After separation and landing, the lander weighed about 600 kilograms and the orbiter about 900 kilograms. The total launch mass was 2,328 kilograms, with 1,445 kilograms of that being propellant and attitude control gas. The ring-shaped structure had eight faces, each 0.457 meters high, with alternating widths of 1.397 and 0.508 meters. The whole thing stood 3.29 meters tall from the lander attachment points at the
- Launch dates
- Viking 1: August 20, 1975; Viking 2: September 9, 1975
- Mars landing dates
- Viking 1: July 20, 1976; Viking 2: September 3, 1976
- Program termination
- 1982
- Project cost
- Roughly US$1 billion at launch (about $6 billion in 2024)
- Total launch mass
- 2,328 kg (5,132 lb)
- Lander mass after landing
- About 600 kg (1,300 lb)
- Orbiter mass after separation
- 900 kg (2,000 lb)
Lore & Background
The Viking program grew from NASA's earlier Voyager Mars program, unrelated to the later Voyager deep space probes. Each spacecraft comprised an orbiter and a lander; the orbiters photographed the surface from orbit and served as communication relays for the landers. Viking 1 entered Mars orbit on June 19, 1976, and Viking 2 on August 7. After more than a month of orbital imaging for landing site selection, the landers detached and soft-landed at chosen sites. The Viking 1 lander touched down on July 20, 1976, and Viking 2 on September 3. The orbiters continued imaging and scientific operations from orbit while the landers deployed instruments on the surface. The program terminated in 1982.
Reader's Guide
The Viking program was considered successful and formed most of the body of knowledge about Mars through the late 1990s and early 2000s. Its science objectives included obtaining high-resolution images, characterizing the atmosphere and surface, and searching for evidence of life. The orbiters discovered many geological forms typically formed from large amounts of water, revolutionizing ideas about water on Mars. They found huge river valleys, branched stream networks in the southern hemisphere, and regions called 'Chaotic Terrain' that seemed to have quickly lost great volumes of water. The landers were sterilized at 111 °C for 40 hours to prevent contamination. Astronomer Carl Sagan helped choose landing sites. The project cost roughly US$1 billion at launch, equivalent to about $6 billion in 2024.
Did You Know?
- Each lander was sterilized at 111 °C for 40 hours to prevent contamination of Mars by Earth organisms.
- The orbiters' solar panels comprised 34,800 solar cells and produced 620 W of power at Mars.
- The Viking program grew from NASA's earlier Voyager Mars program, which was not related to the successful Voyager deep space probes.
- Astronomer Carl Sagan helped choose landing sites for both Viking probes.
Frequently Asked Questions
What are the Viking program derelict landers?
They are two nearly identical NASA spacecraft that touched down on Mars in 1976 and have sat abandoned on the planet's surface ever since.
Where and when did Viking 1 and Viking 2 land?
Viking 1 set down on July 20, 1976, with Viking 2 following on September 3 of the same year. Both probes had launched from Earth in 1975.
What did each Viking spacecraft consist of?
Every probe carried two main parts: an orbiter that photographed Mars from above and a lander that conducted surface experiments. After touchdown, the orbiters also served as communication relays for their respective landers.
When did the Viking program officially end?
NASA terminated the program in 1982, leaving both landers permanently derelict on the Martian surface with no further human contact.
What earlier NASA concept gave rise to the Viking program?
The project grew out of a more ambitious earlier proposal known as Voyager Mars, a name that has no relation to the subsequent Voyager deep-space missions.
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