Space and Astronomy Atlas

How The Universe Works
Missions and Programs

Viking Program

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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
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
Cross-Tradition Connections

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Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationViking program, lead section
Quote, Viking program, lead section
The Viking program consisted of a pair of identical American space probes
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationViking program, lead section (launch)
Quote, Viking program, lead section (launch)
Viking 1 was launched on August 20, 1975
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationViking program, Science objectives section
Quote, Viking program, Science objectives section
Obtain high-resolution images of the Martian surface
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationOperated By: NASA, Viking program, Specifications table
Quote, Operated By: NASA, Viking program, Specifications table
Operator NASA / JPL
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.
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 chemistryWikipedia (space and spaceflight articles)

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