Liquid water and life on Mars

摘要

Many objections have been raised to challenge a biological interpretation of the 1976 Viking Mission Labeled Release (LR) life detection experiment on Mars. Over the years, they have dwindled in the face of the failure of experiments and theories to demonstrate a nonbiological alternative. Recently, NASA's chief scientist, responding to the rapidly accumulating knowledge about life in extreme environments, reduce the remaining obstacles to a single one: the lack of liquid water. A model is consistent with the thermodynamics of the triple point of water. Viking and Pathfinder meteorological data are congruent with the model, as are Viking Lander images of deposits of water ice-frost and snow on the ground. The amounts of soil moisture predicted by the model are within the moisture content range of terrestrial soils in which the LR detected living microorganisms. The last objection to a biological interpretation of the LR Mars data is thus met. Consequential recommendations for the near-term planetary program are made.