Missions and Programs

Viking Program

Robotic Mars Exploration Missions

A pair of identical robotic missions, Viking 1 and Viking 2, that each combined an orbiter and a lander to explore Mars. Both launched in 1975 and landed in 1976; Viking 1 was the first mission to land safely on Mars and return images from the surface. The landers carried the first biological experiments sent to another planet, whose inconclusive results left the question of microbial life on Mars unresolved, and the orbiters' imagery of ancient river valleys transformed scientific understanding of the planet through the late 1990s.

Facts
Mission Type
Paired Mars orbiter-and-lander mission 1
Launch Date
1975-08-20 1
End Date
1983-05-21 1
Outcome
Viking 1 achieved the first fully successful landing on Mars; the program's orbital imagery and its inconclusive biology experiments shaped scientific understanding of Mars for two decades, and the question of microbial life on Mars remains unresolved. 2
Target
Mars 3
Outcome
Success 3
Crewed
No 3
Mission Type
Mission Type (category)
Orbiter 1
Mission Type (category)
Lander / Rover 1
Connections

Open Questions

Operated By

Source Wikipedia (space and spaceflight articles)
Additional Source Viking program (Wikipedia)Article text

Spacecraft Of

Viking 1, Spacecraft
Source Wikipedia: Viking 1
Viking 2, Spacecraft
Source Viking 2 (Wikipedia)

Targets

Source Mars (Wikipedia)
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia Foundation
  • Mission Type (category): Orbiter
  • Mission Type (category): Lander / Rover
  • Mission Type: Paired Mars orbiter-and-lander mission
  • Launch Date: 1975-08-20
  • End Date: 1983-05-21
2. NASA Solar System Exploration
National Aeronautics and Space AdministrationNASA Science, Viking 1 mission page
Quote, NASA Science, Viking 1 mission page
NASA's Viking 1 made the first truly successful landing on Mars.
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3. Viking program (Wikipedia)
  • Lead paragraph
    a pair of identical American space probes, Viking 1 and Viking 2 both launched in 1975
  • Lead paragraph, target
    landed on Mars in 1976
  • Viking program, lead section
    The Viking program consisted of a pair of identical American space probes
  • Viking program, lead section (launch)
    Viking 1 was launched on August 20, 1975
  • Viking program, Science objectives section
    Obtain high-resolution images of the Martian surface
  • Viking program, Wikipedia, infobox (End of mission)
    The Viking program ended on May 21, 1983.
  • Operated By: NASA, Article text
    The mission effort began in 1968 and was managed by the NASA Langley Research Center.
  • In Group: NASA Mars Missions, Lead sentence
    The Viking program consisted of a pair of identical American space probes, Viking 1 and Viking 2 both launched in 1975, and landed on Mars in 1976.
View the Source
Mars (Wikipedia)
Targets: Mars, Article text
Quote, Targets: Mars, Article text
After the results of the Viking life-detection experiments, the hypothesis of a dead planet was generally accepted.
View the Source
Viking 2 (Wikipedia)
  • Includes: Viking 2, Lead paragraph, part-of
    The Viking 2 mission is part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission.
  • Spacecraft Of: Viking 2, Lead paragraph, mission-of
    The Viking 2 mission is part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission.
View the Source
Wikipedia: Viking 1
Wikimedia Foundation
  • Spacecraft Of: Viking 1, Article text
    Viking 1 is the first of two spacecraft, along with Viking 2, each consisting of an orbiter and a lander, sent to Mars as part of NASA's Viking program.
  • Includes: Viking 1, Article text
    Viking 1 is the first of two spacecraft, along with Viking 2, each consisting of an orbiter and a lander, sent to Mars as part of NASA's Viking program.
View the Source
Open Questions (1 open question)
Were the positive results from the Viking landers' biological experiments evidence of microbial life on Mars, or can they be explained by non-biological chemistry in the Martian soil?

The Viking landers' Labeled Release experiment produced results initially read as consistent with biological metabolism, but most scientists later concluded the same results were more likely caused by non-biological, highly oxidizing chemical reactions in the Martian soil. No follow-up mission has definitively settled which explanation is correct.

What would resolve this A mission capable of directly detecting biological molecules or organisms in Martian soil, rather than inferring metabolism indirectly from gas-exchange chemistry, or a complete explanation of the Labeled Release results from soil chemistry alone that leaves no ambiguity.
Astrobiology and planetary soil chemistryViking program (Wikipedia)

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