“Because false negatives in biology do not present…acute risks,” the authors write, “they receive much less attention. Nevertheless, they are still missed opportunities to detect life.”
One of the most-cited examples of the power of no in exobiological experiments occurred during the missions of the Viking 1 and 2 spacecraft, which landed on Mars on July 20, 1976 and Sept. 3, 1976 respectively. During the course of the missions, the twin spacecraft scooped up samples of Martian soil and treated them with nutrients, water, and heat, to see if the samples would show signs of biology, such as releasing radioactively tagged carbon gasses, or absorbing carbon monoxide and carbon dioxide in the soil. In at least two of the studies such possible signs of Martian metabolism were detected, but again, scientists dismissed the results since abiotic processes could account for the reactions too.
