The “Wolf trap” was a life-detection instrument designed by American microbiologist Wolf Vishniac for the Viking mission, which landed on Mars in 1976. Due to budget cuts, it was not included on either lander. The principle of the Wolf trap was to bring martian dust into a tube containing nutrients in liquid form. The instrument would then monitor the state of the liquid; if its pH or cloudiness changed after the martian dust was introduced, this would be an indication of life. Three other culture-based experiments were part of the Viking biology payload instead, but none measured direct changes in a liquid that was designed to support growth.
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