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Vikings on Mars

NASA’s 1976 Search for Life


Annie Prud’homme-Genereux
Continuing Studies and Executive Education
Capilano University


Three experiments carried out by the Mars Viking landers in 1976 remain, to this day, our only attempt to detect life on another planet. All other efforts have looked for the presence of elements or conditions thought to be necessary for life rather than for the presence of life itself. This case study struggles with the difficulties of designing experiments to detect life when there is no consensus as to what life is. Students play the role of interns working at NASA where they propose experiments, work to understand the actual experiments carried out, analyze the data, and propose revised experiments. This case requires between one and three hours to complete, depending on the format used (jigsaw or two variations on an interrupted case, explained in the teaching notes). Little background is required. The case has been used in both an astrobiology course and a freshmen general biology course for non-majors, and works equally well either to introduce the question "what is life" or to review the topic at the end of a course.


  • Identify characteristics that distinguish life from non-life.
  • Recognize assumptions (and levels of assumptions) inherent in the design of experiments to detect life.
  • Design experiments to detect the presence of life.
  • Become aware of the difficulty in designing such experiments (and the assumptions that must be made along the way).
  • Gain knowledge about the experiments performed by the Mars Viking landers to assess the presence of life and their results.
  • Predict and critically evaluate the results of experiments.
  • Come to a consensus about conclusions that can be drawn from the Viking missions.
  • Use information about challenges encountered during the Viking missions, and current knowledge, to propose improved experiments.


Mars; Viking; astrobiology; definition of life; what is life; metabolism; catabolism; anabolism; NASA; extraterrestrial; isotope; labeled release; pyrolytic release

Topical Areas


Educational Level

High school, Undergraduate lower division, Undergraduate upper division, Graduate



Type / Methods

Interrupted, Jig-Saw, Role-Play



Subject Headings

Astronomy  |   Biochemistry  |   Biology (General)  |   Interdisciplinary Sciences  |   Microbiology  |   Science (General)  |  

Date Posted


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